12th Class Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank

done Case Based (MCQs) - Current Electricity Total Questions - 60

• question_answer1)

  Direction: Q.1 to Q.5

  According to Ohm's law, the current flowing through a conductor is directly proportional to the potential difference across the ends of the conductor i.e., \[I\propto V\Rightarrow \frac{V}{I}=R\], where R is resistance of the conductor. Electrical resistance of a conductor is the obstruction posed by the conductor to the flow of electric current through it. It depends upon length, area of cross-section, nature of material and temperature of the conductor. We can write, \[R\propto \frac{l}{A}\] or \[R=\rho \frac{l}{A}\],where \[\rho \] is electrical resistivity of the material of the conductor.

  Read the above passage carefully and give the answer of the following questions.

  Dimensions of electric resistance is:
  A)
  \[[M{{L}^{2}}{{T}^{-2}}{{A}^{-2}}]\]         done clear
  B)
  \[[M{{L}^{2}}{{T}^{-3}}{{A}^{-2}}]\] done clear
  C)
  \[[{{M}^{-1}}{{L}^{-2}}{{T}^{-1}}A]\]                    done clear
  D)
  \[[{{M}^{-1}}{{L}^{2}}{{T}^{2}}{{A}^{-1}}]\] done clear
  View Solution play_arrow

• question_answer2)
  If \[1\mu A\] current flows through a conductor when potential difference of 2V is applied across its ends, then the resistance of the conductor is:
  A)
  \[2\times {{10}^{6}}\Omega \]              done clear
  B)
  \[3\times {{10}^{5}}\Omega \] done clear
  C)
  \[1.5\times {{10}^{5}}\Omega \]                       done clear
  D)
  \[5\times {{10}^{7}}\Omega \] done clear
  View Solution play_arrow

• question_answer3)
  Specific resistance of a wire depends upon:
  A)
  length               done clear
  B)
  cross-sectional area done clear
  C)
  mass                done clear
  D)
  None of these done clear
  View Solution play_arrow

• question_answer4)
  The slope of the graph between potential difference and current through a conductor is:
  A)
  a straight line         done clear
  B)
  curve done clear
  C)
  first curve then straight line done clear
  D)
  first straight line then curve done clear
  View Solution play_arrow

• question_answer5)
  The resistivity of the material of a wire 1.0 m long, 0.4 mm in diameter and having a resistance of \[2.0\,\Omega \] is
  A)
  \[1.57\times {{10}^{-6}}\,\Omega m\] done clear
  B)
  \[5.25\times {{10}^{-7}}\,\Omega m\] done clear
  C)
  \[7.12\times {{10}^{-5}}\,\Omega m\]    done clear
  D)
  \[2.55\times {{10}^{-7}}\,\Omega m\] done clear
  View Solution play_arrow

• question_answer6)

  Direction: Q.6 to Q.10

  The flow of charge in a particular direction constitutes the electric current. Current is measured in Ampere. Quantitatively, electric current in a conductor across an area held perpendicular to the direction of flow of charge is defined as the amount of charge is flowing across that area per unit time.

  Current density at a point in a conductor is the ratio of the current at that point in the conductor to the area of cross-section of the conductor of that point.

  The given figure shows a steady current flows in a metallic conductor of non-uniform cross-section. Current density depends inversely on area, so, here \[{{J}_{1}}>{{J}_{2}}\], as \[{{A}_{1}}<{{A}_{2}}\].

  Read the above passage carefully and give the answer of the following questions.

  What is the current flowing through a conductor, if one million electrons are crossing in one millisecond through a cross-section of it?                                    
  A)
              \[2.5\times {{10}^{-10}}A\]               done clear
  B)
  \[1.6\times {{10}^{-10}}A\] done clear
  C)
              \[7.5\times {{10}^{-9}}A\]                    done clear
  D)
  \[8.2\times {{10}^{-11}}A\] done clear
  View Solution play_arrow

• question_answer7)
  SI unit of electric current is:
  A)
  Cs                     done clear
  B)
  \[N{{s}^{-2}}\]     done clear
  C)
  \[C{{s}^{-1}}\]                        done clear
  D)
  \[{{C}^{-1}}{{s}^{-1}}\] done clear
  View Solution play_arrow

• question_answer8)
  A steady current flows in a metallic conductor of non-uniform cross-section. Which of these quantities is constant along the conductor?                        
  A)
  Electric field            done clear
  B)
  Drift velocity           done clear
  C)
  Current                          done clear
  D)
  Current density done clear
  View Solution play_arrow

• question_answer9)
  A constant current / is flowing along the length of a conductor of variable cross-section as shown in the figure. The quantity which does not depend upon the area of cross-section is
  A)
  electron density               done clear
  B)
  current density        done clear
  C)
  drift velocity            done clear
  D)
  electric field                     done clear
  View Solution play_arrow

• question_answer10)
  When a current of 40 A flows through a conductor of area \[10\,{{m}^{2}}\], then the current density is:
  A)
  \[4\text{ }A/{{m}^{2}}\] done clear
  B)
  \[1\text{ }A/{{m}^{2}}\]  done clear
  C)
  \[2A/{{m}^{2}}\]                     done clear
  D)
  \[8\text{ }A/{{m}^{2}}\] done clear
  View Solution play_arrow

• question_answer11)

  Direction: Q.11 to Q.15

  Metals have a large number of free electrons nearly \[{{10}^{28}}\] per cubic metre. In the absence of electric field, average terminal speed of the electrons in random motion at room temperature is of the order of \[{{10}^{5}}m{{s}^{-1}}\]. When a potential difference V is applied across the two ends of a given conductor, the free electrons in the conductor experiences a force and are accelerated towards the positive end of the conductor. On their way, they suffer frequent collisions with the ions/atoms of the conductor and lose their gained kinetic energy. After each collision, the free electrons are gain accelerated due to electric field, towards the positive end of the conductor and lose their gained kinetic energy in the next collision with the ions/atoms of the conductor. The average speed of the free electrons with which they drift towards the positive end of the conductor under the effect of applied electric field is called drift speed of the electrons.

  Read the above passage carefully and give the answer of the following questions.

  Magnitude of drift velocity per unit electric field is      
  A)
  current density        done clear
  B)
  current                    done clear
  C)
  resistivity                       done clear
  D)
  mobility     done clear
  View Solution play_arrow

• question_answer12)
  The drift speed of the electrons depends on:           
  A)
  dimensions of the conductor           done clear
  B)
  number density of free electrons in the conductor       done clear
  C)
  Both (a) and (b) done clear
  D)
  Neither (a) nor (b) done clear
  View Solution play_arrow

• question_answer13)
           We are able to obtain fairly large currents in a conductor because:
  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 speds 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
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• question_answer14)
  Drift speed of electrons in a conductor is very small i.e., \[i={{10}^{-4}}m{{s}^{-1}}\]. The electric bulb glows immediately. When the switch is closed because:
  A)
  drift velocity of electron increases when switch is closed    done clear
  B)
  electrons are accelerated towards the negative end of the conductor done clear
  C)
  the drifting of electrons takes place at the entire length of the conductor                                     done clear
  D)
  the electrons of conductor move towards the positive end and protons of conductor move towards negative end of the conductor done clear
  View Solution play_arrow

• question_answer15)
  The number density of free electrons in a copper conductor is \[8.5\times {{10}^{28}}{{m}^{-3}}\]. How long does an electron take to drift from one end of a wire 3.0 m long to its other end? The area of cross-section of the wire is \[2.0\times {{10}^{-6}}{{m}^{2}}\] and it is carrying a current of 3.0 A.
  A)
  \[8.1\times {{10}^{4}}s\]          done clear
  B)
  \[2.7\times {{10}^{4}}s\] done clear
  C)
  \[9\times {{10}^{3}}s\]             done clear
  D)
  \[3\times {{10}^{3}}s\] done clear
  View Solution play_arrow

• question_answer16)

  Direction: Q.16 to Q.20

  The resistance of a conductor at temperature \[t{}^\circ C\]is given by \[{{R}_{t}}={{R}_{0}}(1+\alpha t)\]

  where R, is the resistance at t° C, Ry is the resistance at \[0{}^\circ C\] and \[\alpha \] is the characteristics constants of the material of the conductor.

  Over a limited range of temperatures, that is not too large. The resistivity of a metallic conductor is approximately given by \[{{\rho }_{t}}={{\rho }_{0}}(1+\alpha t)\].

  where, \[\alpha \] is the temperature coefficient of resistivity. Its unit is \[{{K}^{-1}}\] or \[{}^\circ {{C}^{-1}}\].

  For metals, a is positive i.e., resistance increases with rise in temperature.

  For insulators and semiconductors, \[\alpha \] is negative i.e., resistance decreases with rise in temperature.

  Read the above passage carefully and give the answer of the following questions.

  Fractional increase in resistivity per unit increase in temperature is defined as
  A)
  resistivity done clear
  B)
  temperature coefficient of resistivity done clear
  C)
  conductivity done clear
  D)
  drift velocity done clear
  View Solution play_arrow

• question_answer17)
  The material whose resistivity is insensitive to temperature is
  A)
  silicon                            done clear
  B)
  copper  done clear
  C)
  silver                             done clear
  D)
  nichrome done clear
  View Solution play_arrow

• question_answer18)
  The temperature coefficient of the resistance of a wire is 0.00125 per \[{}^\circ C\] At 300 K its resistance is \[1\Omega \]. The resistance of wire will be \[2\,\Omega \] at                        
  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_answer19)
  The temperature coefficient of resistance of an alloy used for making resistors is                                
  A)
  small and positive    done clear
  B)
  small and negative  done clear
  C)
  large and positive    done clear
  D)
  large and negative done clear
  View Solution play_arrow

• question_answer20)
       For a metallic wire, the ratio V/l (V = applied potential difference and l = current flowing) is
  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_answer21)

  Direction: Q.21 to Q.25

  In physics, an electric power measure of the rate of electrical energy transfer by an electric circuit per unit time. It is denoted by P and measured using the SI unit of power is the watt or one joule per second. Electric power is commonly supplied by sources such as electric batteries and produced by electric generators.

  The formula for electric power is given by P = VI

  where, P is the power, V is the potential difference in the  circuit, I is the electric current

  Power can also be written as

  \[P={{I}^{2}}R\] and \[P={{V}^{2}}/R\]

  The above two expressions are got by using Ohm's law, where, voltage, current and resistance are related by the following relation

  \[V=IR\]

  where, R is the resistance in the circuit, V is the potential difference in the circuit, I is the electric current.

  The given figure shows four bulbs 1, 2, 3 and 4, consume same power. The resistance of bulb 1 is \[36\,\Omega \].

  Read the above passage carefully and give the answer of the following questions.

  What is the resistance of the bulb 3?
  A)
  \[4\text{ }\Omega \]                    done clear
  B)
  \[\text{9 }\Omega \] done clear
  C)
  \[\text{18 }\Omega \]                 done clear
  D)
  \[\text{12 }\Omega \] done clear
  View Solution play_arrow

• question_answer22)
  What is the resistance of bulb 4?                     
  A)
  \[4\,\Omega \]                            done clear
  B)
  \[8\,\Omega \] done clear
  C)
  \[9\,\Omega \]                            done clear
  D)
  \[18\,\Omega \] done clear
  View Solution play_arrow

• question_answer23)
  If power of each bulb is 4 W, then the total current flowing through the circuit is:                                
  A)
  1 A                               done clear
  B)
  2 A     done clear
  C)
  4 A                               done clear
  D)
  12 A           done clear
  View Solution play_arrow

• question_answer24)
  What is the equivalent resistance of the circuit?        
  A)
  \[12\,\Omega \]                           done clear
  B)
  \[8\,\Omega \] done clear
  C)
  \[18\,\Omega \]               done clear
  D)
  \[16\,\Omega \] done clear
  View Solution play_arrow

• question_answer25)
  What is the voltage output of the battery, if the power of each bulb is 4 W?
  A)
  16 V                             done clear
  B)
  12 V done clear
  C)
  24 V                             done clear
  D)
  18 V done clear
  View Solution play_arrow

• question_answer26)

  Direction: Q.26 to Q.30

  Emf of a cell is the maximum potential difference between two electrodes of the cell when no current is drawn from the cell. Internal resistance is the resistance offered by the electrolyte of a cell when the electric current flows through it. The internal resistance of a cell depends upon the following factors; (i) distance between the electrodes   (ii)   nature   and temperature of the electrolyte (iii) nature of electrodes (iv) area of electrodes.

  For a freshly prepared cell, the value of internal resistance is generally low and goes on increasing as the cell is put to more and more use. The potential difference between the two electrodes of a cell in a closed circuit is called terminal potential difference and its value is always less than the emf of the cell in a closed circuit. It can be written as

  \[V=\varepsilon -Ir\].

  Read the above passage carefully and give the answer of the following questions.

  The terminal potential difference of two electrodes of a cell is equal to emf of the cell when:
  A)
  \[l\ne 0\]                        done clear
  B)
  \[l=0\] done clear
  C)
  Both (a) and (b)      done clear
  D)
  Neither (a) nor (b) done clear
  View Solution play_arrow

• question_answer27)
  A cell of emf \[\varepsilon \] and internal resistance r gives a current of 0.5 A with an external resistance of \[12\,\Omega \] and a current of 0.25 A with an external resistance of \[25\,\Omega \]. What is the value of internal resistance of the cell?
  A)
  \[5\,\Omega \]                            done clear
  B)
  \[1\,\Omega \] done clear
  C)
  \[7\,\Omega \]                            done clear
  D)
  \[3\,\Omega \] done clear
  View Solution play_arrow

• question_answer28)
  Choose the wrong statement.
  A)
  Potential difference across the terminals of a cell in a closed circuit is always less than its emf done clear
  B)
  internal resistance of a cell decrease with the decrease in temperature of the electrolyte done clear
  C)
  Potential difference versus current graphs for a cell is a straight line with a -ve slope done clear
  D)
  Terminal potential difference of the cell when it is being charged is given as \[V=\varepsilon +lr\] done clear
  View Solution play_arrow

• question_answer29)
  An external resistance R is connected to a cell of internal resistance r, the maximum current flows in the external resistance, when:
  A)
  R = r                            done clear
  B)
  R < r    done clear
  C)
  R > r                            done clear
  D)
  R = 1/r done clear
  View Solution play_arrow

• question_answer30)
  If external resistance connected to a cell has been increased to 5 times, the potential difference across the terminals of the cell increases from 10V to 30 V. Then, the emf of the cell is:
  A)
  30 V                 done clear
  B)
  60 V    done clear
  C)
  50 V                             done clear
  D)
  40 V done clear
  View Solution play_arrow

• question_answer31)

  Direction: Q.31 to Q.35

  A single cell provides a feeble current. In order to get a higher current in a circuit, we often use a combination of cells. A combination of cells is called a battery. Cells can be joined in series, parallel or in a mixed way.

  Two cells are said to be connected in series when negative terminal of one cell is connected to positive terminal of the other cell and so on. Two cells are said to be connected in parallel, if positive terminal of each cell is connected to one point and negative terminal of each cell connected to the other point. In mixed grouping of cells, a certains number of identical cells are joined in series, and all such rows are then connected in parallel with each other.

  Read the above passage carefully and give the answer of the following questions.

  To draw the maximum current from a combination of cells, how should the cells be grouped?
  A)
  Parallel done clear
  B)
  Series done clear
  C)
  Mixed grouping done clear
  D)
  Depends upon the relative values of internal and external resistances done clear
  View Solution play_arrow

• question_answer32)
  The total emf of the cells when n identical cells each of emf \[\varepsilon \] are connected in parallel is:
  A)
  \[n\varepsilon \]                          done clear
  B)
  \[{{n}^{2}}\varepsilon \] done clear
  C)
  \[\varepsilon \]                done clear
  D)
  \[\frac{\varepsilon }{n}\] done clear
  View Solution play_arrow

• question_answer33)
  4 cells each of emf 2 V and internal resistance of \[1\,\Omega \]are connected in parallel to a load resistor of \[2\,\Omega \]. Then the current through the load resistor is
  A)
  2 A                               done clear
  B)
  1.5 A     done clear
  C)
  1 A                               done clear
  D)
  0.888 A        done clear
  View Solution play_arrow

• question_answer34)
  If two cells out of n number of cells each of internal resistance ‘r’ are wrongly connected in series, then total resistance of the cell is
  A)
  2nr                    done clear
  B)
  nr - 4r  done clear
  C)
  nr                     done clear
  D)
  r                     done clear
  View Solution play_arrow

• question_answer35)

  Two identical non-ideal batteries are connected in parallel. Consider the following statements.

  (i) The equivalent emf is smaller than either of the two emfs.

  (ii) The equivalent internal resistance is smaller than either of the two internal resistances.

  A)
  Both (i) and (ii) are correct done clear
  B)
  (i) is correct but (ii) is wrong done clear
  C)
  (ii) is correct but (i) is wrong done clear
  D)
  Both (i) and (ii) are wrong done clear
  View Solution play_arrow

• question_answer36)

  Direction: Q.36 to Q.40

  Kirchhoff s circuit laws are two equalities that deal with the current and potential difference in the lumped element model of electrical circuits. They were first described in 1845 by German physicist Gustav Kirchhoff.

  Kirchhoff’s Current Law

  This law states that, for any node in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node.

  Kirchhoff’s Voltage Law

  The directed sum of the potential differences (voltages) around any closed loop is zero.

  Read the above passage carefully and give the answer of the following questions:

  Kirchhoff s current law is conservation of:            
  A)
  charge done clear
  B)
  energy  done clear
  C)
  potential                        done clear
  D)
  momentum             done clear
  View Solution play_arrow

• question_answer37)
              Kirchhoff’s current law can be written as:
  A)
  \[\Sigma \,V=0\]   done clear
  B)
  \[\Sigma \,l=0\] done clear
  C)
  \[\Sigma \,R=0\]             done clear
  D)
  \[\Sigma \,q=0\] done clear
  View Solution play_arrow

• question_answer38)
  Kirchhoff’s voltage law is the conservation of:
  A)
  energy                           done clear
  B)
  charge done clear
  C)
  current              done clear
  D)
  momentum done clear
  View Solution play_arrow

• question_answer39)
  Kirchhoff’s voltage law is applied over:
  A)
  closed circuit loop   done clear
  B)
  at a circuit node done clear
  C)
  across battery        done clear
  D)
  None of these done clear
  View Solution play_arrow

• question_answer40)
  The value of l in the figure shown is:
  A)
  19 A           done clear
  B)
                21 A   done clear
  C)
  4 A                   done clear
  D)
  8 A                       done clear
  View Solution play_arrow

• question_answer41)

  Direction: Q.41 to Q.45

  In 1942, a German physicist Kirchhoff’s extended Ohm's law to complicated circuits and gave two laws, which enable us to determine current in any part of such a circuit. According to Kirchhoff’s first rule, the algebraic sum of the currents meeting at a junction in a closed electric circuit is zero. The current flowing in a conductor towards the junction is taken as positive and the current flowing away from the junction is taken as negative. According to Kirchhoff’s second rule, in a closed loop, the algebraic sum of the emf’s and algebraic sum of the products of current and resistance in the various emf of the loop is zero. While traversing a loop, if negative pole of the cell is encountered first, then its emf is negative, otherwise positive.

  Read the above passage carefully and give the answer of the following questions:

  The value of current / in the given circuit is:
  A)
  4.5 A                            done clear
  B)
  3.7 A     done clear
  C)
  2.0 A                            done clear
  D)
  2.5 A done clear
  View Solution play_arrow

• question_answer42)
  Point out the right statements about the validity of Kirchhoff's Junction rule.
  A)
  The current flowing towards the junction are taken as positive done clear
  B)
  The currents flowing away from the junction are taken as negative done clear
  C)
  Bending or reorienting the wire does not change the validity of Kirchhoff's Junction rule done clear
  D)
  All of the above done clear
  View Solution play_arrow

• question_answer43)
  Potential difference between A and B in the circuit shown here is
  A)
  4 V                               done clear
  B)
  5.6 V    done clear
  C)
  2.8 V                            done clear
  D)
  6 V done clear
  View Solution play_arrow

• question_answer44)
  A 5 V battery of negligible internal resistance is connected across a 200 V battery and a resistance of \[39\text{ }\Omega \] as shown in the figure. The value of current is
  A)
  5 A                               done clear
  B)
  3 A      done clear
  C)
  4 A                               done clear
  D)
  7.8 A done clear
  View Solution play_arrow

• question_answer45)
  Between any two points in a circuit, the sum of all………..is the same through any pathway.
  A)
  charge              done clear
  B)
  current done clear
  C)
  resistance                       done clear
  D)
  potential difference done clear
  View Solution play_arrow

• question_answer46)

  Direction: Q.46 to Q.50

  A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of the circuit is its ability to provide extremely accurate measurements.

  The resistance is adjusted until the bridge is "balanced" and no current flows through the galvanometer. At this point, the voltage between the two mid-points (B and D) will be zero.

  Therefore the ratio of the two resistances in the known leg is equal to the ratio of the two resistances in the unknown leg.

  Read the above passage carefully and give the answer of the following questions:

  In balanced Wheatstone bridge:                   
  A)
  potential at points B and D remain same done clear
  B)
  large current flows through the circuit done clear
  C)
  battery becomes over heated                         done clear
  D)
  resistances become small                        done clear
  View Solution play_arrow

• question_answer47)
  Wheatstone bridge is used to measure:
  A)
  unknown current    done clear
  B)
  unknown voltage done clear
  C)
  unknown charge     done clear
  D)
  unknown resistance done clear
  View Solution play_arrow

• question_answer48)
  Wheatstone bridge is implemented in lab using
  A)
  ammeter                        done clear
  B)
  voltmeter done clear
  C)
  meter bridge         done clear
  D)
  potentiometer done clear
  View Solution play_arrow

• question_answer49)
  Condition for balanced Wheatstone bridge:
  A)
  \[{{R}_{1}}/{{R}_{2}}={{R}_{3}}/{{R}_{x}}\]    done clear
  B)
  \[{{R}_{3}}={{R}_{1}}\times {{R}_{x}}\] done clear
  C)
  \[{{R}_{1}}={{R}_{3}}\times {{R}_{x}}\]          done clear
  D)
  None of these done clear
  View Solution play_arrow

• question_answer50)
  Wheatstone bridge is analogous to:
  A)
  cantilevel                       done clear
  B)
  simple level system done clear
  C)
  gear train                       done clear
  D)
  mechanical clutch done clear
  View Solution play_arrow

• question_answer51)
            

  Direction: Q.51 to Q.55

  Potentiometer: Potentiometer is a device which is used to find out the emf of any cell and it is also used to find the potential difference across any two points on a conductor correctly. In this device as long wire of manganin or constantan, copper strips, binding screws etc. are used. The principle of potentiometer is given as, the decrease in potential across any part of the wire is directly proportional to the length of that part of wire, provided the current and area of cross-section of the wire remain same.

  Read the above passage carefully and give the answer of the following questions:

  Potentiometer (Rheostat) is used to find out
  A)
  emf                   done clear
  B)
  potential difference done clear
  C)
  Both (a) and (b)      done clear
  D)
  None of these done clear
  View Solution play_arrow

• question_answer52)
  The wire used in potentiometer is made of the material:
  A)
  constantan           done clear
  B)
  gold done clear
  C)
  iron                   done clear
  D)
  silver done clear
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• question_answer53)
  The metallic strips used in potentiometer are made of:
  A)
  copper               done clear
  B)
  iron done clear
  C)
  gold                  done clear
  D)
  manganin done clear
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• question_answer54)
  The decrease in potential across the wire is proportional to the length of the wire
  A)
  directly     done clear
  B)
  inversely done clear
  C)
  Both (a) and (b)         done clear
  D)
  None of these done clear
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• question_answer55)
  The potentiometer will give accurate result, if the area of cross-section of the wire
  A)
  increases           done clear
  B)
  decrease done clear
  C)
  remain same        done clear
  D)
  None of these done clear
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• question_answer56)

  Direction: Q.56 to Q.60

  Potentiometer is an apparatus used for measuring the emf of a cell or potential difference between two points in an electrical circuit accurately. It is also used to determine the internal resistance of a primary cell. The potentiometer is based on the principle that, if V is the potential difference across any portion of the wire of length l and resistance R, then \[V\propto l\] or \[V=kl\] where k is the potential gradient. Thus, potential difference across any portion of potentiometer wire is directly proportional to length of the wire of that portion. The potentiometer wire must be uniform. The resistance of potentiometer wire should be high.

  Read the above passage carefully and give the answer of the following questions:

  Which one of the following is true about potentiometer?
  A)
  Its sensitivity is low done clear
  B)
  It measures the emf of a cell very accurately     done clear
  C)
  It is based on deflection method                       done clear
  D)
  None of the above                                  done clear
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• question_answer57)
           A current of 1.0 mA is flowing through a potentiometer wire of length 4 cm and of resistance \[4\,\Omega \]. The potential gradient of the potentiometer wire is
  A)
              \[{{10}^{-3}}V{{m}^{-1}}\] done clear
  B)
  \[{{10}^{-5}}V{{m}^{-2}}\] done clear
  C)
              \[2\times {{10}^{-3}}V{{m}^{-1}}\] done clear
  D)
  \[4\times {{10}^{-3}}V{{m}^{-1}}\] done clear
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• question_answer58)
  Sensitivity of a potentiometer can be increased by:
  A)
  decreasing potential gradient along the wire done clear
  B)
  increasing potential gradient along the wire done clear
  C)
  decreasing current through the wire done clear
  D)
  increasing current through the wire done clear
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• question_answer59)
  A potentiometer is an accurate and versatile device to make electrical measurements of emf because the method involves
  A)
  potential gradient done clear
  B)
  a condition of no current flow through the galvanometer done clear
  C)
  a combination of cells, galvanometer and resistances done clear
  D)
  cells done clear
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• question_answer60)
  In a potentiometer experiment, the balancing length is 8m, when the two cells \[{{E}_{1}}\] and \[{{E}_{2}}\] are joined in series. When the two cells are connected in opposition the balancing lengths is 4 m. The ratio of emf of two cells \[({{E}_{1}}/{{E}_{2}})\] is
  A)
  \[1:2\]                            done clear
  B)
  \[2:1\] done clear
  C)
  \[1:3\]                            done clear
  D)
  \[3:1\] done clear
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