JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank

done Electric Conduction, Ohm's and Resistance Total Questions - 133

• question_answer1)
  Current of 4.8 amperes is flowing through a conductor. The number of electrons per second will be        [CPMT 1986]
  A)
                     \[3\times {{10}^{19}}\] done clear
  B)
             \[7.68\times {{10}^{21}}\] done clear
  C)
                     \[7.68\times {{10}^{20}}\]                                           done clear
  D)
             \[3\times {{10}^{20}}\] done clear
  View Solution play_arrow

• question_answer2)
  When the current \[i\] is flowing through a conductor, the drift velocity is \[v\]. If  \[2i\]  current is flowed through the same metal but having double the area of cross-section, then the drift velocity will be
  A)
                                                                                                                                           \[v/4\]                             done clear
  B)
             \[v/2\] done clear
  C)
                     \[v\] done clear
  D)
                                       \[4v\] done clear
  View Solution play_arrow

• question_answer3)
  When current flows through a conductor, then the order of drift velocity of electrons will be                      [CPMT 1986]
  A)
                     \[{{10}^{10}}\,m/\sec \]   done clear
  B)
             \[{{10}^{-2}}\,cm/\sec \] done clear
  C)
                     \[{{10}^{4}}\,cm/\sec \] done clear
  D)
                                       \[{{10}^{-1}}\,cm/\sec \] done clear
  View Solution play_arrow

• question_answer4)
  Every atom makes one free electron in copper. If 1.1 ampere current is flowing in the wire of copper having 1 mm diameter, then the drift velocity (approx.) will be (Density of copper \[=9\times {{10}^{3}}\,kg\,{{m}^{-3}}\] and atomic weight = 63) [CPMT 1989]
  A)
                     \[0.3\,mm/\sec \]       done clear
  B)
             \[0.1\,mm/\sec \] done clear
  C)
                     \[0.2\,mm/\sec \]       done clear
  D)
                     \[0.2\,cm/\sec \] done clear
  View Solution play_arrow

• question_answer5)
  Which one is not the correct statement             [NCERT 1978]
  A)
             \[1\,volt\times 1\,coulomb=1\,joule\] done clear
  B)
                     \[1\,volt\times 1\,ampere=1\,joule/second\] done clear
  C)
                     \[1\,volt\times 1\,watt=1\,H.P.\] done clear
  D)
                     Watt-hour can be expressed in eV done clear
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• question_answer6)
  If a 0.1 % increase in length due to stretching, the percentage increase in its resistance will be            [MNR 1990; MP PMT 1996; UPSEAT 1999; MP PMT 2000]
  A)
                     0.2 %                                done clear
  B)
             2 % done clear
  C)
                     1 %                                    done clear
  D)
             0.1 % done clear
  View Solution play_arrow

• question_answer7)
  The specific resistance of managing is \[50\times {{10}^{-8}}\,ohm\times m\]. The resistance of a cube of length \[50\,cm\] will be
  A)
                     \[{{10}^{-6}}\,ohm\] done clear
  B)
             \[2.5\times {{10}^{-5}}\,ohm\] done clear
  C)
                                  \[{{10}^{-8}}\,ohm\]       done clear
  D)
                  \[5\times {{10}^{-4}}\,ohm\] done clear
  View Solution play_arrow

• question_answer8)
                                       The resistivity of iron is\[1\times {{10}^{-7}}\,ohm-m\]. The resistance of a iron wire of particular length and thickness is 1 ohm. If the length and the diameter of wire both are doubled, then the resistivity in \[ohm-m\] will be                          [CPMT 1983; DPMT 1999]
  A)
                     \[1\times {{10}^{-7}}\] done clear
  B)
             \[2\times {{10}^{-7}}\] done clear
  C)
                     \[4\times {{10}^{-7}}\]      done clear
  D)
             \[8\times {{10}^{-7}}\] done clear
  View Solution play_arrow

• question_answer9)
  The temperature coefficient of resistance for a wire is \[0.00125/{}^\circ C\]. At 300K its resistance is 1 ohm. The temperature at which the resistance becomes 2 ohm is                                 [IIT 1980; MP PET 2002; KCET 2003; MP PMT 2001; Orissa JEE 2002]
  A)
                     1154 K done clear
  B)
                                       1100 K done clear
  C)
                     1400 K                              done clear
  D)
             1127 K done clear
  View Solution play_arrow

• question_answer10)
  When the length and area of cross-section both are doubled, then its resistance                                              [MP PET 1989]
  A)
                     Will become half          done clear
  B)
             Will be doubled done clear
  C)
                     Will remain the same done clear
  D)
             Will become four times done clear
  View Solution play_arrow

• question_answer11)
  The resistance of a wire is 20 ohms. It is so stretched that the length becomes three times, then the new resistance of the wire will be                                                      [MP PET 1989]
  A)
                     6.67 ohms                       done clear
  B)
             60.0 ohms done clear
  C)
                     120 ohms                        done clear
  D)
             180.0 ohms done clear
  View Solution play_arrow

• question_answer12)
  The resistivity of a wire                      [MP PMT 1984; DPMT 1982]
  A)
                     Increases with the length of the wire done clear
  B)
                     Decreases with the area of cross-section done clear
  C)
                     Decreases with the length and increases with the cross-section of wire done clear
  D)
                     None of the above statement is correct done clear
  View Solution play_arrow

• question_answer13)
  Ohm's law is true
  A)
                     For metallic conductors at low temperature done clear
  B)
                     For metallic conductors at high temperature done clear
  C)
                     For electrolytes when current passes through them done clear
  D)
                     For diode when current flows done clear
  View Solution play_arrow

• question_answer14)
  The example for non-ohmic resistance is       [MP PMT 1978]
  A)
                     Copper wire                  done clear
  B)
             Carbon resistance done clear
  C)
                     Diode done clear
  D)
             Tungston wire done clear
  View Solution play_arrow

• question_answer15)
  Drift velocity \[{{v}_{d}}\] varies with the intensity of electric field as per the relation                                      [CPMT 1981; BVP 2003]
  A)
                     \[{{v}_{d}}\propto E\] done clear
  B)
             \[{{v}_{d}}\propto \frac{1}{E}\] done clear
  C)
                     \[{{v}_{d}}=\text{constant}\]                                    done clear
  D)
             \[{{v}_{d}}\propto {{E}^{2}}\] done clear
  View Solution play_arrow

• question_answer16)
  On increasing the temperature of a conductor, its resistance increases because                                                [CPMT 1982]
  A)
                     Relaxation time decreases done clear
  B)
                     Mass of the electrons increases done clear
  C)
                     Electron density decreases done clear
  D)
                     None of the above done clear
  View Solution play_arrow

• question_answer17)
  In a conductor 4 coulombs of charge flows for 2 seconds. The value of electric current will be      [CPMT 1984]
  A)
                     4 volts                              done clear
  B)
             4 amperes done clear
  C)
                     2 amperes                      done clear
  D)
             2 volts done clear
  View Solution play_arrow

• question_answer18)
  The specific resistance of a wire is \[\rho \], its volume is 3\[{{m}^{3}}\] and its resistance is 3 ohms, then its length will be                                                                                              [CPMT 1984]
  A)
                     \[\sqrt{\frac{1}{\rho }}\] done clear
  B)
                                       \[\frac{3}{\sqrt{\rho }}\] done clear
  C)
                     \[\frac{1}{\rho }\sqrt{3}\]                                           done clear
  D)
             \[\rho \sqrt{\frac{1}{3}}\] done clear
  View Solution play_arrow

• question_answer19)
  \[62.5\times {{10}^{18}}\] electrons per second are flowing through a wire of area of cross-section 0.1\[{{m}^{2}}\], the value of current flowing will be                                                                          [CPMT 1984]
  A)
                     1 A done clear
  B)
                                       0.1 A done clear
  C)
                     10 A done clear
  D)
                     0.11 A done clear
  View Solution play_arrow

• question_answer20)
  A piece of wire of resistance 4 ohms is bent through \[180{}^\circ \] at its mid-point and the two halves are twisted together, then the resistance is                                                                [CPMT 1971]
  A)
                     8 ohms done clear
  B)
                                       1 ohm done clear
  C)
                     2 ohms done clear
  D)
                                       5 ohms done clear
  View Solution play_arrow

• question_answer21)
  When a piece of aluminium wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance will become                                 [NCERT 1974; AIIMS 1997; MH CET 2000; UPSEAT 2001; CBSE PMT 2002]
  A)
                                                       Two times done clear
  B)
                                       Four times done clear
  C)
                     Eight times                     done clear
  D)
             Sixteen times done clear
  View Solution play_arrow

• question_answer22)
  A wire 100\[cm\] long and 2.0\[mm\] diameter has a resistance of 0.7 ohm, the electrical resistivity of the material is
  A)
                     \[4.4\times {{10}^{-6}}ohm\times m\] done clear
  B)
                                       \[2.2\times {{10}^{-6}}ohm\times m\] done clear
  C)
                     \[1.1\times {{10}^{-6}}ohm\times m\]                  done clear
  D)
             \[0.22\times {{10}^{-6}}ohm\times m\] done clear
  View Solution play_arrow

• question_answer23)
  A certain wire has a resistance \[R\]. The resistance of another wire identical with the first except having twice its diameter is                                                                                                         [CPMT 1999]
  A)
                     \[2\,R\] done clear
  B)
                                       \[0.25\,R\] done clear
  C)
                     \[4\,R\] done clear
  D)
                                       \[0.5\,R\] done clear
  View Solution play_arrow

• question_answer24)
  In hydrogen atom, the electron makes \[6.6\times {{10}^{15}}\] revolutions per second around the nucleus in an orbit of radius \[0.5\times {{10}^{-10}}m\]. It is equivalent to a current nearly
  A)
                     1 A done clear
  B)
                                       1 mA                                                                                                                     done clear
  C)
                     \[1\,\mu A\]                  done clear
  D)
             \[1.6\times {{10}^{-19}}A\] done clear
  View Solution play_arrow

• question_answer25)
  A wire of length 5\[m\] and radius 1\[mm\] has a resistance of 1 ohm. What length of the wire of the same material at the same temperature and of radius 2\[mm\] will also have a resistance of 1 ohm
  A)
                     1.25\[m\] done clear
  B)
                                       2.5\[m\] done clear
  C)
                     10\[m\] done clear
  D)
                                       20\[m\] done clear
  View Solution play_arrow

• question_answer26)
  When there is an electric current through a conducting wire along its length, then an electric field must exist
  A)
                     Outside the wire but normal to it done clear
  B)
                     Outside the wire but parallel to it done clear
  C)
                     Inside the wire but parallel to it done clear
  D)
                     Inside the wire but normal to it done clear
  View Solution play_arrow

• question_answer27)
  Through a semiconductor, an electric current is due to drift of
  A)
                     Free electrons done clear
  B)
                     Free electrons and holes done clear
  C)
                     Positive and negative ions done clear
  D)
                     Protons done clear
  View Solution play_arrow

• question_answer28)
  In an electrolyte \[3.2\times {{10}^{18}}\] bivalent positive ions drift to the right per second while \[3.6\times {{10}^{18}}\] monovalent negative ions drift to the left per second. Then the current is
  A)
                     1.6 amp to the left      done clear
  B)
             1.6 amp to the right done clear
  C)
                     0.45 amp to the right done clear
  D)
                     0.45 amp to the left done clear
  View Solution play_arrow

• question_answer29)
  A metallic block has no potential difference applied across it, then the mean velocity of free electrons is \[T\] = absolute temperature of the block)
  A)
                     Proportional to \[T\] done clear
  B)
                     Proportional to \[\sqrt{T}\] done clear
  C)
                     Zero done clear
  D)
                     Finite but independent of temperature done clear
  View Solution play_arrow

• question_answer30)
  The specific resistance of all metals is most affected by
  A)
                     Temperature                done clear
  B)
             Pressure done clear
  C)
                     Degree of illumination      done clear
  D)
             Applied magnetic field done clear
  View Solution play_arrow

• question_answer31)
  The positive temperature coefficient of resistance is for
  A)
                     Carbon done clear
  B)
                                       Germanium done clear
  C)
                     Copper                            done clear
  D)
             An electrolyte done clear
  View Solution play_arrow

• question_answer32)
  The fact that the conductance of some metals rises to infinity at some temperature below a few Kelvin is called
  A)
                     Thermal conductivity         done clear
  B)
             Optical conductivity done clear
  C)
                     Magnetic conductivity      done clear
  D)
             Superconductivity done clear
  View Solution play_arrow

• question_answer33)
  Dimensions of a block are \[1\,cm\times 1\,cm\times 100\,cm\]. If specific resistance of its material is \[3\times {{10}^{-7}}ohm-m\], then the resistance between the opposite rectangular faces is                                                                                            [MP PET 1993]
  A)
                     \[3\times {{10}^{-9}}ohm\]                                        done clear
  B)
             \[3\times {{10}^{-7}}ohm\] done clear
  C)
                     \[3\times {{10}^{-5}}ohm\]                                        done clear
  D)
             \[3\times {{10}^{-3}}ohm\] done clear
  View Solution play_arrow

• question_answer34)
  In the above question, the resistance between the square faces is                                          [MP PET 1993]
  A)
                     \[3\times {{10}^{-9}}ohm\] done clear
  B)
                                       \[3\times {{10}^{-7}}ohm\] done clear
  C)
                     \[3\times {{10}^{-5}}ohm\]                                        done clear
  D)
             \[3\times {{10}^{-3}}ohm\] done clear
  View Solution play_arrow

• question_answer35)
  There is a current of 20 amperes in a copper wire of \[{{10}^{-6}}\] square metre area of cross-section. If the number of free electrons per cubic metre is \[{{10}^{29}}\], then the drift velocity is
  A)
                     \[125\times {{10}^{-3}}m/sec\] done clear
  B)
                                       \[12.5\times {{10}^{-3}}m/sec\] done clear
  C)
                     \[1.25\times {{10}^{-3}}m/sec\]                               done clear
  D)
             \[1.25\times {{10}^{-4}}m/sec\] done clear
  View Solution play_arrow

• question_answer36)
  The electric intensity \[E\], current density \[j\] and specific resistance \[k\] are related to each other by the relation [DPMT 2001]
  A)
                     \[E=j/k\]                         done clear
  B)
             \[E=jk\] done clear
  C)
                     \[E=k/j\]                         done clear
  D)
             \[k=jE\] done clear
  View Solution play_arrow

• question_answer37)
  The resistance of a wire of uniform diameter \[d\] and length \[L\] is \[R\]. The  resistance of another wire of the same material but diameter \[2d\] and length \[4L\] will be [CPMT 1984; MP PET 2002]
  A)
                     \[2R\] done clear
  B)
                                       \[R\] done clear
  C)
                     \[R/2\] done clear
  D)
                                       \[R/4\] done clear
  View Solution play_arrow

• question_answer38)
  There is a current of 1.344 amp in a copper wire whose area of cross-section normal to the length of the wire is 1\[m{{m}^{2}}\]. If the number of free electrons per \[c{{m}^{3}}\] is \[8.4\times {{10}^{22}}\], then the drift velocity would be                                                                          [CPMT 1990]
  A)
                     1.0\[mm/sec\]             done clear
  B)
             1.0\[m/sec\] done clear
  C)
                     0.1\[mm/sec\]             done clear
  D)
             0.01\[mm/sec\] done clear
  View Solution play_arrow

• question_answer39)
  It is easier to start a car engine on a hot day than on a cold day. This is because the internal resistance of the car battery
  A)
                     Decreases with rise in temperature done clear
  B)
                     Increases with rise in temperature done clear
  C)
                     Decreases with a fall in temperature done clear
  D)
                     Does not change with a change in temperature done clear
  View Solution play_arrow

• question_answer40)
  5 amperes of current is passed through a metallic conductor. The charge flowing in one minute in coulombs will be [MP PET 1984]
  A)
                     5 done clear
  B)
                                       12 done clear
  C)
                     1/12                                  done clear
  D)
             300 done clear
  View Solution play_arrow

• question_answer41)
  Two wires of the same material are given. The first wire is twice as long as the second and has twice the diameter of the second. The resistance of the first will be                                                                                          [MP PMT 1993]
  A)
                     Twice of the second   done clear
  B)
             Half of the second done clear
  C)
                     Equal to the second   done clear
  D)
             Four times of the second done clear
  View Solution play_arrow

• question_answer42)
  An electric wire is connected across a cell of e.m.f. E. The current \[I\] is measured by an ammeter of resistance R. According to ohm's law                                          [MP PMT 1993]
  A)
                     \[E={{I}^{2}}R\] done clear
  B)
                                       \[E=IR\] done clear
  C)
                     \[E=R/I\]                         done clear
  D)
             \[E=I/R\] done clear
  View Solution play_arrow

• question_answer43)
  The resistances of a wire at temperatures \[t{}^\circ C\] and \[0{}^\circ C\] are related by                                            [MP PMT 1993]
  A)
                     \[{{R}_{t}}={{R}_{0}}(1+\alpha \,t)\] done clear
  B)
                                       \[{{R}_{t}}={{R}_{0}}(1-\alpha \,t)\] done clear
  C)
                     \[{{R}_{t}}=R_{0}^{2}(1+\alpha \,t)\]                     done clear
  D)
             \[{{R}_{t}}=R_{0}^{2}(1-\alpha \,t)\]                              done clear
  View Solution play_arrow

• question_answer44)
  An electric wire of length ?I? and area of cross-section \[a\] has a resistance R ohms. Another wire of the same material having same length and area of cross-section 4a has a resistance of                                         [MP PMT 1993]
  A)
                     4R                                      done clear
  B)
             R/4 done clear
  C)
                     R/16                                  done clear
  D)
             16R done clear
  View Solution play_arrow

• question_answer45)
  For which of the following the resistance decreases on increasing the temperature                                         [MP PET 1993]
  A)
                     Copper done clear
  B)
                                       Tungsten done clear
  C)
                     Germanium                   done clear
  D)
             Aluminium done clear
  View Solution play_arrow

• question_answer46)
  If \[n,\,e,\,\tau \] and m respectively represent the density, charge relaxation time and mass of the electron, then the resistance of a wire of length \[l\] and area of cross-section \[A\] will be [CPMT 1992]
  A)
                     \[\frac{ml}{n{{e}^{2}}\tau A}\] done clear
  B)
                                       \[\frac{m{{\tau }^{2}}A}{n{{e}^{2}}l}\] done clear
  C)
                     \[\frac{n{{e}^{2}}\tau A}{2ml}\] done clear
  D)
                                       \[\frac{n{{e}^{2}}A}{2m\tau l}\] done clear
  View Solution play_arrow

• question_answer47)
  The relaxation time in conductors                         [DPMT 2003]
  A)
                     Increases with the increase of temperature done clear
  B)
                     Decreases with the increase of temperature done clear
  C)
                     It does not depend on temperature done clear
  D)
                     All of sudden changes at 400 K done clear
  View Solution play_arrow

• question_answer48)
  Which of the following statement is correct
  A)
                     Liquids obey fully the ohm's law done clear
  B)
                     Liquids obey partially the ohm's law done clear
  C)
                     There is no relation between current and p.d. for liquids done clear
  D)
                     None of the above done clear
  View Solution play_arrow

• question_answer49)
  A certain piece of silver of given mass is to be made like a wire. Which of the following combination of length (L) and the area of cross-sectional  will lead to the smallest resistance    [MP PMT 1995; CBSE PMT 1997]
  A)
                     L and A done clear
  B)
             2L and A/2 done clear
  C)
             L/2 and 2 A done clear
  D)
             Any of the above, because volume of silver remains same done clear
  View Solution play_arrow

• question_answer50)
  The resistance of a wire is\[10\,\Omega \]. Its length is increased by 10% by stretching. The new resistance will now be [CPMT 2000; Pb PET 2004]
  A)
                     \[12\,\Omega \] done clear
  B)
             \[1.2\,\Omega \] done clear
  C)
                     \[13\,\Omega \]          done clear
  D)
             \[11\,\Omega \] done clear
  View Solution play_arrow

• question_answer51)
  Resistance of tungsten wire at \[150{}^\circ C\] is \[133\,\Omega \]. Its resistance temperature coefficient is \[0.0045/{}^\circ C\]. The resistance of this wire at \[500{}^\circ C\] will be           [DPMT 2004]
  A)
                     \[180\,\Omega \] done clear
  B)
                                       \[225\,\Omega \] done clear
  C)
                     \[258\,\Omega \]        done clear
  D)
                                                                \[317\,\Omega \] done clear
  View Solution play_arrow

• question_answer52)
  A metal wire of specific resistance \[64\times {{10}^{-6}}ohm-cm\] and length 198 cm has a resistance of  7 ohm, the radius of the wire will be                                         [MP PET 1994]
  A)
                     2.4 cm done clear
  B)
                                       0.24 cm done clear
  C)
                     0.024 cm                          done clear
  D)
             24 cm done clear
  View Solution play_arrow

• question_answer53)
  A copper wire of length 1 m and radius 1 mm is joined in series with an iron wire of length 2 m and radius 3 mm and a current is passed through the wires. The ratio of the current density in the copper and iron wires is [MP PMT 1994]
  A)
                     18 : 1 done clear
  B)
                                       9 : 1 done clear
  C)
                     6 : 1                                   done clear
  D)
             2 : 3 done clear
  View Solution play_arrow

• question_answer54)
  For a metallic wire, the ratio \[V/i\] \[(V=\] the applied potential difference, i = current flowing) is           [MP PMT 1994; BVP 2003]
  A)
                     Independent of temperature done clear
  B)
                     Increases as the temperature rises done clear
  C)
                     Decreases as the temperature rises done clear
  D)
                     Increases or decreases as temperature rises, depending upon the metal done clear
  View Solution play_arrow

• question_answer55)
  The resistance of a wire is R. If the length of the wire is doubled by stretching, then the new resistance will be [Roorkee 1992; AFMC 1995; KCET 1993; AMU (Med.) 1999; CBSE PMT 1999; MP PET 2001; UPSEAT 2001]
  A)
                     2R done clear
  B)
                                       4R done clear
  C)
                     R                                         done clear
  D)
             \[\frac{R}{4}\] done clear
  View Solution play_arrow

• question_answer56)
  Which of the following has a negative temperature coefficient                                  [AFMC 1995]
  A)
                     C                                         done clear
  B)
             Fe done clear
  C)
                     Mn                                    done clear
  D)
             Ag done clear
  View Solution play_arrow

• question_answer57)
  The reciprocal of resistance is                                  [AFMC 1995]
  A)
                     Conductance                 done clear
  B)
             Resistivity done clear
  C)
                     Voltage                            done clear
  D)
             None of the above done clear
  View Solution play_arrow

• question_answer58)
  A solenoid is at potential difference 60 V and current flows through it is 15 ampere, then the resistance of coil will be [AFMC 1995]
  A)
                     \[4\,\Omega \] done clear
  B)
                                       \[8\,\Omega \] done clear
  C)
                     \[0.25\,\Omega \]       done clear
  D)
             \[2\,\Omega \] done clear
  View Solution play_arrow

• question_answer59)
  All of the following statements are true except [Manipal MEE 1995]
  A)
                     Conductance is the reciprocal of resistance and is measured in Siemens done clear
  B)
                     Ohm's law is not applicable at very low and very high temperatures done clear
  C)
                     Ohm's law is applicable to semiconductors done clear
  D)
                     Ohm's law is not applicable to electron tubes, discharge tubes and electrolytes done clear
  View Solution play_arrow

• question_answer60)
  A potential difference of V is applied at the ends of a copper wire of length l and diameter d. On doubling only d, drift velocity                                                      [MP PET 1995]
  A)
                     Becomes two times   done clear
  B)
             Becomes half done clear
  C)
                     Does not change         done clear
  D)
             Becomes one fourth done clear
  View Solution play_arrow

• question_answer61)
  If the resistance of a conductor is 5 W at 50oC and 7 W at 100oC then the mean temperature coefficient of resistance of the material is                                                          [Pb PET 2000]
  A)
             \[0.008{{/}^{o}}C\] done clear
  B)
                                       \[0.006{{/}^{o}}C\] done clear
  C)
             \[0.004{{/}^{o}}C\]             done clear
  D)
             \[0.001{{/}^{o}}C\] done clear
  View Solution play_arrow

• question_answer62)
  The resistance of a discharge tube is                                                                    [AFMC 1996; CBSE PMT 1999]
  A)
                                                       Ohmic                                      done clear
  B)
             Non-ohmic done clear
  C)
                     Both A and B                 done clear
  D)
             Zero done clear
  View Solution play_arrow

• question_answer63)
  We are able to obtain fairly large currents in a conductor because                                             [Haryana CEE 1996]
  A)
                     The electron drift speed is usually very large done clear
  B)
                     The number density of free electrons is very high and this can compensate for the low values of the electron drift speed and the very small magnitude of the electron charge done clear
  C)
                     The number density of free electrons as well as the electron drift speeds are very large and these compensate for the very small magnitude of the electron charge done clear
  D)
                     The very small magnitude of the electron charge has to be divided by the still smaller product of the number density and drift speed to get the electric current done clear
  View Solution play_arrow

• question_answer64)
  A platinum resistance thermometer has a resistance of \[50\,\Omega \] at \[20{}^\circ C\]. When dipped in a liquid the resistance becomes \[76.8\,\Omega \]. The temperature coefficient of resistance for platinum is \[\alpha =3.92\times {{10}^{-3}}/{}^\circ C\]. The temperature of the liquid is
  A)
             \[100{}^\circ C\] done clear
  B)
                                       \[137{}^\circ C\] done clear
  C)
                     \[167{}^\circ C\]           done clear
  D)
             \[200{}^\circ C\] done clear
  View Solution play_arrow

• question_answer65)
  In a wire of circular cross-section with radius r, free electrons travel with a drift velocity V when a current I flows through the wire. What is the current in another wire of half the radius and of the same material when the drift velocity is 2V          [MP PET 1997]
  A)
                     2I done clear
  B)
                                       I done clear
  C)
                     \[I/2\]                              done clear
  D)
             \[I/4\] done clear
  View Solution play_arrow

• question_answer66)
  The resistivity of a wire depends on its    [MP PMT/PET 1998]
  A)
                     Length done clear
  B)
                                       Area of cross-section done clear
  C)
                     Shape                               done clear
  D)
             Material done clear
  View Solution play_arrow

• question_answer67)
  The conductivity of a superconductor is [Similar to KCET 1993; MP PMT/PET 1998]
  A)
                     Infinite done clear
  B)
                                       Very large done clear
  C)
                     Very small                      done clear
  D)
             Zero done clear
  View Solution play_arrow

• question_answer68)
  In a neon discharge tube \[2.9\times {{10}^{18}}\,N{{e}^{+}}\] ions move to the right each second while \[1.2\times {{10}^{18}}\] electrons move to the left per second. Electron charge is \[1.6\times {{10}^{-19}}C\]. The current in the discharge tube                                                             [MP PET 1999]
  A)
                     1 A towards right         done clear
  B)
             0.66 A towards right done clear
  C)
                     0.66 A towards left     done clear
  D)
             Zero done clear
  View Solution play_arrow

• question_answer69)
  A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/ quantities constant along the length of the conductor is/are                                      [KCET 1994, IIT 1997 Cancelled; CBSE PMT 2001]
  A)
                     Current, electric field and drift speed done clear
  B)
                     Drift speed only done clear
  C)
                     Current and drift speed done clear
  D)
                     Current only done clear
  View Solution play_arrow

• question_answer70)
  The resistivity of alloys \[={{R}_{\text{alloy}}}\]; the resistivity of constituent metals \[{{R}_{\text{metal}}}\]. Then, usually                                                        [KCET 1994]
  A)
             \[{{R}_{\text{alloy}}}={{R}_{\text{metal}}}\] done clear
  B)
                     \[{{R}_{\text{alloy}}}<{{R}_{\text{metal}}}\] done clear
  C)
                     There is no simple relation between \[{{R}_{\text{alloy}}}\] and \[{{R}_{\text{metal}}}\] done clear
  D)
                     \[{{R}_{\text{alloy}}}>{{R}_{\text{metal}}}\] done clear
  View Solution play_arrow

• question_answer71)
  Two wires A and B of same material and same mass have radius 2rand r. If resistance of wire A is \[34\,\Omega \], then resistance of B will be                                         [RPET 1997]
  A)
                     \[544\,\Omega \] done clear
  B)
                                       \[272\,\Omega \] done clear
  C)
                     \[68\,\Omega \]          done clear
  D)
             \[17\,\Omega \] done clear
  View Solution play_arrow

• question_answer72)
  Two rods of same material and length have their electric resistance in ratio \[1:2\]. When both rods are dipped in water, the correct statement will be                                                       [RPMT 1997]
  A)
                     A has more loss of weight done clear
  B)
                     B has more loss of weight done clear
  C)
                     Both have same loss of weight done clear
  D)
                     Loss of weight will be in the ratio \[1:2\] done clear
  View Solution play_arrow

• question_answer73)
  \[20\,\mu A\] current flows for 30 seconds in a wire, transfer of charge will be                                   [RPMT 1997]
  A)
             \[2\times {{10}^{-4}}C\]   done clear
  B)
             \[4\times {{10}^{-4}}C\] done clear
  C)
                     \[6\times {{10}^{-4}}C\]      done clear
  D)
             \[8\times {{10}^{-4}}C\] done clear
  View Solution play_arrow

• question_answer74)
  \[{{\sigma }_{1}}\] and \[{{\sigma }_{2}}\] are the electrical conductivities of Ge and Na respectively. If these substances are heated, then
  A)
                     Both \[{{\sigma }_{1}}\] and \[{{\sigma }_{2}}\] increase done clear
  B)
                     \[{{\sigma }_{1}}\] increases and \[{{\sigma }_{2}}\] decreases done clear
  C)
                     \[{{\sigma }_{1}}\] decreases and \[{{\sigma }_{2}}\] increases done clear
  D)
                     Both \[{{\sigma }_{1}}\] and \[{{\sigma }_{2}}\] decrease done clear
  View Solution play_arrow

• question_answer75)
  1.6 mA current is flowing in conducting wire then the number of electrons flowing per second is               [RPMT 1999]
  A)
             \[\text{1}{{0}^{\text{11}}}\]  done clear
  B)
             \[\text{1}{{0}^{\text{16}}}\] done clear
  C)
             \[\text{1}{{0}^{\text{19}}}\]  done clear
  D)
             \[\text{1}{{0}^{\text{15}}}\] done clear
  View Solution play_arrow

• question_answer76)
  A current I is passing through a wire having two sections P and Q of uniform diameters d and d/2 respectively.  If the mean drift velocity of electrons in sections P and Q is denoted by vP and vQ respectively, then    [Roorkee 1999]
  A)
             \[{{v}_{\text{P}}}={{v}_{\text{Q}}}\]                             done clear
  B)
             \[{{v}_{\text{P}}}={{v}_{\text{Q}}}\] done clear
  C)
             \[{{v}_{\text{P}}}=\frac{1}{4}{{v}_{\text{Q}}}\] done clear
  D)
             \[{{v}_{\text{P}}}=\text{ 2}{{v}_{\text{Q}}}\] done clear
  View Solution play_arrow

• question_answer77)
  If an electric current is passed through a nerve of a man, then man                                          [UPSEAT 1999]
  A)
   Begins to laugh done clear
  B)
             Begins to weep done clear
  C)
             Is excited done clear
  D)
             Becomes insensitive to pain done clear
  View Solution play_arrow

• question_answer78)
  The resistance of a coil is 4.2 W at 100o C and the temperature coefficient of resistance of its material is 0.004/o C.  Its resistance at 0o C is                                                         [KCET 1999]
  A)
             6.5 W                                        done clear
  B)
             5 W done clear
  C)
             3 W done clear
  D)
             4 W done clear
  View Solution play_arrow

• question_answer79)
  Masses of three wires of copper are in the ratio of 1 : 3 : 5 and their lengths are in the ratio of \[5:3:1.\] The ratio of their electrical resistances are                                 [AFMC 2000]
  A)
             1 : 3 : 5 done clear
  B)
                                       5 : 3 : 1 done clear
  C)
             1 : 15 : 125                              done clear
  D)
             125 : 15 : 1 done clear
  View Solution play_arrow

• question_answer80)
  Conductivity increases in the order of                 [AFMC 2000]
  A)
             Al, Ag, Cu done clear
  B)
             Al, Cu, Ag done clear
  C)
             Cu, Al, Ag                               done clear
  D)
             Ag, Cu, Al done clear
  View Solution play_arrow

• question_answer81)
  A uniform wire of resistance R is uniformly compressed along its length, until its radius becomes n times the original radius.  Now resistance of the wire becomes [KCET 2000]
  A)
             \[\frac{R}{{{n}^{4}}}\]       done clear
  B)
             \[\frac{R}{{{n}^{2}}}\] done clear
  C)
             \[\frac{R}{n}\]                      done clear
  D)
             nR done clear
  View Solution play_arrow

• question_answer82)
  The resistance of a conductor is 5 ohm at 50oC and 6 ohm at 100oC.  Its resistance at  0oC is            [KCET 2000]
  A)
             1 ohm done clear
  B)
                                       2 ohm done clear
  C)
             3 ohm                                      done clear
  D)
             4 ohm done clear
  View Solution play_arrow

• question_answer83)
  If an electron revolves in the path of a circle of radius of \[0.5\text{ }\times \text{ }{{10}^{10}}m\]at frequency of \[5\text{ }\times \text{ }{{10}^{15}}cycles/s\]the electric current in the circle is (Charge of an electron \[=\text{ }1.6\text{ }\times \text{ }{{10}^{19}}C\]) [EAMCET 2000]
  A)
             0.4 mA done clear
  B)
                                       0.8 mA done clear
  C)
             1.2 mA                                     done clear
  D)
             1.6 mA done clear
  View Solution play_arrow

• question_answer84)
  Equal potentials are applied on an iron and copper wire of same length.  In order to have the same current flow in the two wires, the ratio r (iron)/r (copper) of their radii must be (Given that specific resistance of iron = \[1.0\times {{10}^{-7}}\]ohm?m and specific resistance of copper = \[1.7\times {{10}^{-8}}\]ohm-m) [MP PMT 2000]
  A)
             About 1.2 done clear
  B)
                                       About 2.4 done clear
  C)
             About 3.6                               done clear
  D)
             About 4.8 done clear
  View Solution play_arrow

• question_answer85)
  An electron (charge = 1.6 × 10?19 coulomb) is moving in a circle of radius 5.1 × 10?11m at a frequency of 6.8 × 1015 revolutions/sec.  The equivalent current is approximately [MP PET 2000]
  A)
             \[5.1\times {{10}^{-3}}\] amp done clear
  B)
                                       \[6.8\times {{10}^{-3}}\] amp done clear
  C)
             \[1.1\times {{10}^{-3}}\] amp done clear
  D)
             \[2.2\times {{10}^{-3}}\] amp done clear
  View Solution play_arrow

• question_answer86)
  A rod of a certain metal is 1.0 m long and 0.6 cm in diameter.  Its resistance is 3.0 × \[{{10}^{-3}}\] ohm.  Another disc made of the same metal is 2.0 cm in diameter and 1.0 mm thick.  What is the resistance between the round faces of the disc                                                      [MP PET 2000]
  A)
             \[\text{1}.\text{35 }\times ~{{10}^{-8}}hm\]              done clear
  B)
             2.70 × \[{{10}^{-7}}\] ohm done clear
  C)
             4.05 × \[{{10}^{-6}}\] ohm       done clear
  D)
             8.10 × \[{{10}^{-5}}\] ohm done clear
  View Solution play_arrow

• question_answer87)
  At what temperature will the resistance of a copper wire become three times its value at 0oC  (Temperature coefficient of resistance for copper = 4 × 10?3 per oC ) [MP PET 2000]
  A)
             \[{{400}^{o}}C\] done clear
  B)
                                       \[{{450}^{o}}C\] done clear
  C)
             \[{{500}^{o}}C\]                   done clear
  D)
             \[{{550}^{o}}C\] done clear
  View Solution play_arrow

• question_answer88)
  An electron revolves \[6\text{ }\times \text{ }{{10}^{15}}times/sec\]in circular loop.  The current in the loop is                      [MNR 1995; UPSEAT 2000]
  A)
             0.96 mA                                   done clear
  B)
             0.96 m A done clear
  C)
             28.8 A                                       done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer89)
  The charge of an electron is 1.6 × 10?19 C.  How many electrons strike the screen of a cathode ray tube each second when the beam current is 16 mA                 [AMU (Med.) 2000]
  A)
             \[{{10}^{17}}\]                      done clear
  B)
             \[{{10}^{19}}\] done clear
  C)
             \[{{10}^{19}}\]                      done clear
  D)
             \[{{10}^{17}}\] done clear
  View Solution play_arrow

• question_answer90)
  If potential \[V=100\pm 0.5\,Volt\] and current \[I=10\pm 0.2\] amp are given to us.  Then what will be the value of resistance                                                                          [RPET 2001]
  A)
             \[10\pm 0.7\,ohm\] done clear
  B)
                                       \[5\pm 2\,ohm\] done clear
  C)
             \[0.1\pm 0.2ohm\]             done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer91)
  A nichrome wire 50 cm long and one square millimetre cross-section carries a current of 4A when connected to a 2V battery.  The resistivity of nichrome wire in ohm metre is [EAMCET 2001]
  A)
             1 × \[{{10}^{-6}}\] done clear
  B)
                                       4 × \[{{10}^{-7}}\] done clear
  C)
             3 × \[{{10}^{-7}}\]               done clear
  D)
             2 × \[{{10}^{-7}}\] done clear
  View Solution play_arrow

• question_answer92)
  If an observer is moving with respect to a stationary electron, then he observes                                               [DCE 2001]
  A)
             Only magnetic field            done clear
  B)
             Only electric field done clear
  C)
             Both A and B done clear
  D)
             None of the above done clear
  View Solution play_arrow

• question_answer93)
  Calculate the amount of charge flowing in 2 minutes in a wire of resistance 10 W when a potential difference of 20 V is applied between its ends                              [Kerala (Engg.) 2001]
  A)
             120 C                                        done clear
  B)
             240 C done clear
  C)
             20 C                                           done clear
  D)
             4 C done clear
  View Solution play_arrow

• question_answer94)
  If a wire of resistance R is melted and recasted to half of its length, then the new resistance of the wire will be [KCET (Med.) 2001]
  A)
             R/4 done clear
  B)
             R/2 done clear
  C)
             R     done clear
  D)
             2R done clear
  View Solution play_arrow

• question_answer95)
  The drift velocity does not depend upon              [BHU 2001]
  A)
             Cross-section of the wire done clear
  B)
             Length of the wire done clear
  C)
             Number of free electrons       done clear
  D)
             Magnitude of the current done clear
  View Solution play_arrow

• question_answer96)
  There is a current of 40 ampere in a wire of \[{{10}^{-6}}\,{{m}^{2}}\] area of cross-section.  If the number of free electron per \[{{m}^{3}}\] is \[{{10}^{29}}\],  then the drift velocity will be            [Pb. PMT 2001]
  A)
             \[1.25\text{ }\times ~{{10}^{3}}m/s\] done clear
  B)
                                       \[2.50\text{  }\times ~{{10}^{-3}}m/s\] done clear
  C)
             \[25.0\text{  }\times ~{{10}^{-3}}m/s\] done clear
  D)
                                       \[250\text{  }\times ~{{10}^{-3}}m/s\] done clear
  View Solution play_arrow

• question_answer97)
  At room temperature, copper has free electron density of \[8.4\times {{10}^{28}}\] per \[{{m}^{3}}\].  The copper conductor has a cross-section of \[{{10}^{6}}{{m}^{2}}\]and carries a current of 5.4 A.  The electron drift velocity in copper is                                            [UPSEAT 2002]
  A)
             400 m/s done clear
  B)
                                       0.4 m/s done clear
  C)
             0.4 m/s                                    done clear
  D)
             72 m/s done clear
  View Solution play_arrow

• question_answer98)
  The resistance of a 5 cm long wire is 10 W.  It is uniformly stretched so that its length becomes 20 cm.  The resistance of the wire is                                                                [MH CET 2002]
  A)
             160 W                                       done clear
  B)
             80 W done clear
  C)
             40 W                                         done clear
  D)
             20 W done clear
  View Solution play_arrow

• question_answer99)
  The resistance of an incandescent lamp is           [KCET 2002]
  A)
             Greater when switched off    done clear
  B)
             Smaller when switched on done clear
  C)
             Greater when switched on    done clear
  D)
             The same whether it is switched off or switched on done clear
  View Solution play_arrow

• question_answer100)
  In the figure a carbon resistor has bands of different colours on its body as mentioned in the figure.  The value of the resistance is                                                              [Kerala PET 2002]
  A)
             2.2 k W done clear
  B)
             3.3 k W done clear
  C)
             5.6 k W done clear
  D)
             9.1 k W done clear
  View Solution play_arrow

• question_answer101)
  By increasing the temperature, the specific resistance of a conductor and a semiconductor                          [AIEEE 2002]
  A)
             Increases for both              done clear
  B)
             Decreases for both done clear
  C)
             Increases, decreases         done clear
  D)
             Decreases, increases done clear
  View Solution play_arrow

• question_answer102)
  Which of the following is vector quantity           [AFMC 2002]
  A)
             Current density                   done clear
  B)
             Current done clear
  C)
             Wattless current                 done clear
  D)
             Power done clear
  View Solution play_arrow

• question_answer103)
   Masses of 3 wires of same metal are in the ratio 1 : 2 : 3 and their lengths are in the ratio 3 : 2 : 1.  The electrical resistances are in ratio                                                [CPMT 2002]
  A)
             1 : 4 : 9 done clear
  B)
                                       9 : 4 : 1 done clear
  C)
             1 : 2 : 3                                     done clear
  D)
             27 : 6 : 1 done clear
  View Solution play_arrow

• question_answer104)
  A current of 1 mA is flowing through a copper wire.  How many electrons will pass a given point in one second            \[\left[ e=\text{ }1.6\text{ }\times \text{ }{{10}^{19}}Coulomb \right]\]      [RPMT 2000; MP PMT 2002]
  A)
              6.25 × \[{{10}^{19}}\]        done clear
  B)
             6.25 × \[{{10}^{15}}\] done clear
  C)
             6.25 × \[{{10}^{31}}\] done clear
  D)
                                       6.25 × \[{{10}^{8}}\] done clear
  View Solution play_arrow

• question_answer105)
  The drift velocity of free electrons in a conductor is ?v? when a current ?i? is flowing in it.  If both the radius and current are doubled, then drift velocity will be                   [BHU 2002]
  A)
             v     done clear
  B)
             \[\frac{v}{2}\] done clear
  C)
             \[\frac{v}{4}\]                       done clear
  D)
             \[\frac{v}{8}\] done clear
  View Solution play_arrow

• question_answer106)
  A wire of radius r has resistance R.  If it is stretched to a radius of \[\frac{3r}{4}\], its resistance becomes               [BHU 2002]
  A)
             \[\frac{9R}{16}\]                  done clear
  B)
             \[\frac{16R}{9}\] done clear
  C)
             \[\frac{81R}{256}\]             done clear
  D)
             \[\frac{256R}{81}\] done clear
  View Solution play_arrow

• question_answer107)
  The resistance of a conductor increases with [CBSE PMT 2002]
  A)
             Increase in length               done clear
  B)
             Increase in temperature done clear
  C)
             Decrease in cross?sectional area done clear
  D)
             All of these done clear
  View Solution play_arrow

• question_answer108)
  A copper wire has a square cross-section, 2.0 mm on a side.  It carries a current of 8 A and the density of free electrons is \[8\times {{10}^{28}}\,{{m}^{-3}}\]. The drift speed of electrons is equal to [AMU (Med.) 2002]
  A)
             0.156 × \[{{10}^{-3}}\] m.s?1   done clear
  B)
             0.156 × \[{{10}^{-2}}\] m.s?1 done clear
  C)
             3.12 × \[{{10}^{-3}}\] m.s?1     done clear
  D)
             3.12 × \[{{10}^{-2}}\] m.s?1 done clear
  View Solution play_arrow

• question_answer109)
  Two wires of same material have length L and 2L and cross?sectional areas 4A and A respectively.  The ratio of their specific resistance would be             [MHCET 2002]
  A)
             1 : 2                                           done clear
  B)
             8 : 1 done clear
  C)
             1 : 8                                           done clear
  D)
             1 : 1 done clear
  View Solution play_arrow

• question_answer110)
  When a current flows through a conductor its temperature [MHCET 2002]
  A)
             May increase or decrease done clear
  B)
             Remains same done clear
  C)
             Decreases done clear
  D)
             Increases done clear
  View Solution play_arrow

• question_answer111)
  What length of the wire of specific resistance \[48\times {{10}^{-8}}\,\Omega \,\,m\] is needed to make a resistance of   4.2 W (diameter of wire = 0.4 mm) [CBSE PMT 2000; Pb. PMT 2002]
  A)
             4.1 m                                        done clear
  B)
             3.1 m done clear
  C)
             2.1 m                                        done clear
  D)
             1.1 m done clear
  View Solution play_arrow

• question_answer112)
  A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of          [AIEEE 2003]
  A)
             Each of these increases done clear
  B)
                                       Each of these decreases done clear
  C)
             Copper strip increases and that of germanium decreases done clear
  D)
             Copper strip decreases and that of germanium increases done clear
  View Solution play_arrow

• question_answer113)
  The length of a given cylindrical wire is increased by 100 %.  Due to the consequent decrease in diameter the change in the resistance of the wire will be                                                         [AIEEE 2003]
  A)
             300 % done clear
  B)
                                       200 % done clear
  C)
             100 %                                       done clear
  D)
             50 % done clear
  View Solution play_arrow

• question_answer114)
  Express which of the following setups can be used to verify Ohm?s law                  [IIT-JEE (Screening) 2003]
  A)
             done clear
  B)
                              done clear
  C)
                              done clear
  D)
    done clear
  View Solution play_arrow

• question_answer115)
  We have two wires A and B of same mass and same material.  The diameter of the wire A is half of that B.  If the resistance of wire A is 24 ohm then the resistance of wire B will be                                           [CPMT 2003]
  A)
             12 Ohm done clear
  B)
                                       3.0 Ohm done clear
  C)
             1.5 Ohm                                  done clear
  D)
             None of the above done clear
  View Solution play_arrow

• question_answer116)
  In a hydrogen discharge tube it is observed that through a given cross-section \[3.13\times {{10}^{15}}\] electrons are moving from right to left and \[3.12\times {{10}^{15}}\] protons are moving from left to right. What is the electric current in the discharge tube and what is its direction                                     [AFMC 1996]           
  A)
             \[1\,mA\,\]towards right done clear
  B)
             \[1mA\] towards left done clear
  C)
             \[2mA\] towards left         done clear
  D)
             \[2\,mA\] towards right done clear
  View Solution play_arrow

• question_answer117)
  A steady current i is flowing through a conductor of uniform cross-section. Any segment of the conductor has [MP PET 1996]
  A)
             Zero charge done clear
  B)
             Only positive charge done clear
  C)
             Only negative charge done clear
  D)
                     Charge proportional to current i done clear
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• question_answer118)
  The length of the wire is doubled. Its conductance will be                                                                                      [Kerala PMT 2004]
  A)
             Unchanged done clear
  B)
                                       Halved done clear
  C)
                     Quadrupled                   done clear
  D)
             1/4 of the original value done clear
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• question_answer119)
  A source of e.m.f. E = 15 V and having negligible internal resistance is connected to a variable resistance so that the current in the circuit increases with time as i = 1.2 t + 3. Then, the total charge that will flow in first five second will be                                                            [Kerala PMT 2004; J & K CET 2004]
  A)
             10 C done clear
  B)
                                       20 C done clear
  C)
                     30 C done clear
  D)
             40 C done clear
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• question_answer120)
  The new resistance of wire of R W, whose radius is reduced half, is          [J & K CET 2004; Pb PMT 2004]
  A)
             16 R done clear
  B)
                                       3 R done clear
  C)
                     2R                                      done clear
  D)
             R done clear
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• question_answer121)
  A resistance R is stretched to four times its length. Its new resistance will be       [ISM Dhanbad 1994; UPSEAT 2003]
  A)
                     4 R done clear
  B)
                                       64 R done clear
  C)
                     \[R/4\]                             done clear
  D)
             16 R done clear
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• question_answer122)
  What is the resistance of a carbon resistance which has bands of colours brown, black and brown             [DCE 1999]
  A)
             100 W done clear
  B)
             1000 W done clear
  C)
             10 W                                         done clear
  D)
             1 W done clear
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• question_answer123)
  The lead wires should have                                  [Pb. PMT 2000]
  A)
             Larger diameter and low resistance done clear
  B)
             Smaller diameter and high resistance done clear
  C)
             Smaller diameter and low resistance done clear
  D)
             Larger diameter and high resistance done clear
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• question_answer124)
  The alloys constantan and managing are used to make standard resistance due to they have [MH CET 2000; NCERT 1990]
  A)
             Low resistivity done clear
  B)
             High resistivity done clear
  C)
             Low temperature coefficient of resistance done clear
  D)
             Both B and C done clear
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• question_answer125)
  When a potential difference is applied across the ends of a linear metallic conductor       [MP PET 1997]
  A)
                     The free electrons are accelerated continuously from the lower potential end to the higher potential end of the conductor done clear
  B)
                     The free electrons are accelerated continuously from the higher potential end to the lower potential end of the conductor done clear
  C)
                     The free electrons acquire a constant drift velocity from the lower potential end to the higher potential end of the conductor done clear
  D)
             The free electrons are set in motion from their position of rest done clear
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• question_answer126)
  The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then            [CBSE PMT 2004]
  A)
             The resistance will be doubled and the specific resistance will be halved done clear
  B)
             The resistance will be halved and the specific resistance will remain unchanged done clear
  C)
             The resistance will be halved and the specific resistance will be doubled done clear
  D)
             The resistance and the specific resistance, will both remain unchanged done clear
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• question_answer127)
  A wire of diameter 0.02 metre contains 1028 free electrons per cubic metre. For an electrical current of 100 A, the drift velocity of the free electrons in the wire is nearly [UPSEAT 2004]
  A)
             \[1\times {{10}^{19}}m/s\] done clear
  B)
                                       \[5\times {{10}^{10}}m/s\] done clear
  C)
             \[2\times {{10}^{4}}m/s\]       done clear
  D)
             \[8\times {{10}^{3}}m/s\] done clear
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• question_answer128)
  The following four wires are made of the same material and are at the same temperature. Which one of them has highest electrical resistance                                   [UPSEAT 2004]
  A)
             Length = 50 cm, diameter = 0.5 mm done clear
  B)
             Length = 100 cm, diameter = 1 mm done clear
  C)
             Length = 200 cm, diameter = 2 mm done clear
  D)
             Length = 300 cm, diameter = 3 mm done clear
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• question_answer129)
  The colour sequence in a carbon resistor is red, brown, orange and silver. The resistance of the resistor is [DCE 2004]
  A)
             \[21\times {{10}^{3}}\pm 10%\] done clear
  B)
                                       \[23\times {{10}^{1}}\pm 10\] done clear
  C)
             \[21\times {{10}^{3}}\pm 5%\]                                         done clear
  D)
             \[12\times {{10}^{3}}\pm 5%\] done clear
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• question_answer130)
  A thick wire is stretched so that its length become two times. Assuming that there is no change in its density, then what is the ratio of change in resistance of wire to the initial resistance of wire                                   [MH CET 2004]
  A)
             2 : 1                                           done clear
  B)
             4 : 1 done clear
  C)
             3 : 1                                           done clear
  D)
             1 : 4 done clear
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• question_answer131)
  The length of the resistance wire is increased by 10%. What is the corresponding change in the resistance of wire [MH CET 2004]
  A)
             10%                                           done clear
  B)
             25% done clear
  C)
             21%                                           done clear
  D)
             9% done clear
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• question_answer132)
  The electric field E, current density J and conductivity s  of a conductor are related as                                     [Kerala PMT 2005]
  A)
             \[\sigma =E/j\] done clear
  B)
                                       \[\sigma =j/E\] done clear
  C)
             \[\sigma =jE\]                       done clear
  D)
             \[\sigma =1/jE\] done clear
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• question_answer133)
  Two wires that are made up of two different materials whose specific resistance are in the ratio 2 : 3, length 3 : 4 and area 4 : 5. The ratio of their resistances is  [Kerala PMT 2005]
  A)
             6 : 5                                           done clear
  B)
             6 : 8 done clear
  C)
                  5 : 8        done clear
  D)
                  1 : 2 done clear
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