JEE Main & Advanced Physics Electro Magnetic Induction Question Bank

done Application of EMI (Motor, Dynamo, Transformer) Total Questions - 86

• question_answer1)
  Which of the following does not depend upon the magnetic effect of some sort
  A)
              Moving coil galvanometer done clear
  B)
              Hot wire ammeter done clear
  C)
              Dynamo done clear
  D)
              Electric motor done clear
  View Solution play_arrow

• question_answer2)
  Use of eddy currents is done in the following except
  A)
              Moving coil galvanometer     done clear
  B)
              Electric brakes done clear
  C)
              Induction motor                 done clear
  D)
              Dynamo done clear
  View Solution play_arrow

• question_answer3)
   Plane of eddy currents makes an angle with the plane of magnetic lines of force equal to
  A)
             \[{{40}^{o}}\]                        done clear
  B)
             \[{{0}^{o}}\] done clear
  C)
             \[{{90}^{o}}\]                        done clear
  D)
             \[{{180}^{o}}\] done clear
  View Solution play_arrow

• question_answer4)
  Which of the following is constructed on the principle of electromagnetic induction                         [MP PMT 2002]
  A)
              Galvanometer                     done clear
  B)
             Electric motor done clear
  C)
              Generator                             done clear
  D)
             Voltmeter done clear
  View Solution play_arrow

• question_answer5)
  A transformer is based on the principle of  [AIIMS 1998; AFMC 2005]
  A)
              Mutual inductance            done clear
  B)
             Self  inductance done clear
  C)
              Ampere's law                      done clear
  D)
             Lenz's law done clear
  View Solution play_arrow

• question_answer6)
  Which of the following is not an application of eddy currents       [CBSE PMT 1989]
  A)
             Induction furnace               done clear
  B)
             Galvanometer damping done clear
  C)
             Speedometer of automobiles                                           done clear
  D)
             X-ray crystallography done clear
  View Solution play_arrow

• question_answer7)
  The core of a transformer is laminated to reduce energy losses due to [CBSE PMT 1990; Karnataka CET (Med.) 2001]
  A)
             Eddy currents                       done clear
  B)
              Hysteresis done clear
  C)
             Resistance in winding        done clear
  D)
              None of these done clear
  View Solution play_arrow

• question_answer8)
  The pointer of a dead-beat galvanometer gives a steady deflection because                                       [MP PMT 1994]
  A)
             Eddy currents are produced in the conducting frame over which the coil is wound done clear
  B)
             Its magnet is very strong done clear
  C)
             Its pointer is very light done clear
  D)
             Its frame is made of abonite done clear
  View Solution play_arrow

• question_answer9)
  The device that does not work on the principle of mutual induction is                     [KCET 1994]
  A)
             Induction coil                        done clear
  B)
             Motor done clear
  C)
             Tesla coil                                 done clear
  D)
             Transformer done clear
  View Solution play_arrow

• question_answer10)
  Eddy currents are produced when [CBSE PMT 1993; AFMC 2002]
  A)
             A metal is kept in varying magnetic field done clear
  B)
             A metal is kept in the steady magnetic field done clear
  C)
             A circular coil is placed in a magnetic field done clear
  D)
             Through a circular coil, current is passed done clear
  View Solution play_arrow

• question_answer11)
  If rotational velocity of a dynamo armature is doubled, then induced e.m.f. will become               [MP PMT 1991; AIIMS 2000]
  A)
             Half                                           done clear
  B)
             Two times done clear
  C)
             Four times                             done clear
  D)
             Unchanged done clear
  View Solution play_arrow

• question_answer12)
  Dynamo is a device for converting
  A)
             Electrical energy into mechanical energy done clear
  B)
             Mechanical energy into electrical energy done clear
  C)
             Chemical energy into mechanical energy done clear
  D)
             Mechanical energy into chemical energy done clear
  View Solution play_arrow

• question_answer13)
  The working of dynamo is based on principle of [CPMT 1984]
  A)
             Electromagnetic induction done clear
  B)
             Conversion of energy into electricity done clear
  C)
             Magnetic effects of current done clear
  D)
             Heating effects of current done clear
  View Solution play_arrow

• question_answer14)
  Choke coil works on the principle of          [MP PET/PMT 1988]
  A)
             Transient current                done clear
  B)
              Self induction done clear
  C)
             Mutual induction                done clear
  D)
              Wattless current done clear
  View Solution play_arrow

• question_answer15)
  When the speed of a dc motor increases the armature current [CPMT 1984, 85; MP PMT 2004]
  A)
             Increases done clear
  B)
             Decreases done clear
  C)
             Does not change done clear
  D)
             Increases and decreases continuously done clear
  View Solution play_arrow

• question_answer16)
  The output of a dynamo using a splitting commutator is
  A)
             dc done clear
  B)
             ac done clear
  C)
             Fluctuating dc done clear
  D)
             Half-wave rectified voltage done clear
  View Solution play_arrow

• question_answer17)
  Which of the following statement is incorrect
  A)
             Both ac and dc dynamo have a field magnet done clear
  B)
             Both ac and dc dynamo have an armature done clear
  C)
             Both ac and dc dynamo convert mechanical energy into electrical energy done clear
  D)
             Both ac and dc dynamo have slip rings done clear
  View Solution play_arrow

• question_answer18)
  The coil of dynamo is rotating in a magnetic field. The developed induced e.m.f. changes and the number of magnetic lines of force also changes. Which of the following condition is correct                                    [MP PET 1993]
  A)
             Lines of force minimum but induced e.m.f. is zero done clear
  B)
             Lines of force maximum but induced e.m.f. is zero done clear
  C)
             Lines of force maximum but induced e.m.f. is not zero done clear
  D)
             Lines of force maximum but induced e.m.f. is also maximum done clear
  View Solution play_arrow

• question_answer19)
  Dynamo core is laminated because                    [MP PET 1995]
  A)
             Magnetic field increases done clear
  B)
             Magnetic saturation level in core increases done clear
  C)
             Residual magnetism in core decreases done clear
  D)
             Loss of energy in core due to eddy currents decreases done clear
  View Solution play_arrow

• question_answer20)
  Armature current in dc motor will be maximum when [CPMT 1986, 88; MP PET 1995]
  A)
             Motor has acquired maximum speed done clear
  B)
             Motor has acquired intermediate speed done clear
  C)
             Motor has just started moving done clear
  D)
             Motor is switched off done clear
  View Solution play_arrow

• question_answer21)
  The armature of dc motor has \[20\,\Omega \] resistance. It draws current of 1.5 ampere when run by 220 volts dc supply. The value of back e.m.f. induced in it will be [MP PMT 1999]
  A)
             150 V                                        done clear
  B)
             170 V done clear
  C)
             180 V                                        done clear
  D)
             190 V done clear
  View Solution play_arrow

• question_answer22)
  In an induction coil, the secondary e.m.f. is         [KCET 1994]
  A)
             Zero during break of the circuit done clear
  B)
             Very high during make of the circuit done clear
  C)
             Zero during make of the circuit done clear
  D)
             Very high during break of the circuit done clear
  View Solution play_arrow

• question_answer23)
  The number of turns in the coil of an ac­ generator is 5000 and the area of the coil is \[0.25\,{{m}^{2}}\]. The coil is rotated at the rate of 100 cycles/sec in a magnetic field of 0.2\[W/{{m}^{2}}\]. The peak value of the emf generated is nearly      [AMU 1995]
  A)
             786 kV                                      done clear
  B)
             440 kV done clear
  C)
             220 kV                                      done clear
  D)
             157.1 Kv done clear
  View Solution play_arrow

• question_answer24)
  In a dc motor, induced e.m.f. will be maximum [RPMT 1997]
  A)
             When motor takes maximum speed done clear
  B)
             When motor starts rotating done clear
  C)
             When speed of motor increases done clear
  D)
             When motor is switched off done clear
  View Solution play_arrow

• question_answer25)
  Work of electric motor is                                           [RPMT 1997]
  A)
             To convert ac into dc done clear
  B)
             To convert dc into ac done clear
  C)
             Both (a) and (b) done clear
  D)
             To convert ac into mechanical work done clear
  View Solution play_arrow

• question_answer26)
  In an induction coil with resistance, the induced emf will be maximum when                                       [RPMT 1996]
  A)
             The switch is put on due to high resistance done clear
  B)
             The switch is put off due to high resistance done clear
  C)
             The switch is put on due to low resistance done clear
  D)
             The switch is put off due to low resistance done clear
  View Solution play_arrow

• question_answer27)
  An electric motor operating on a 60 V dc supply draws a current of 10 A. If the efficiency of the motor is 50%, the resistance of its winding is                               [AMU (Engg.) 2001]
  A)
             \[3\Omega \]                        done clear
  B)
             \[6\Omega \] done clear
  C)
             \[15\Omega \]                     done clear
  D)
             \[30\Omega \] done clear
  View Solution play_arrow

• question_answer28)
  A device which converts electrical energy into mechanical energy is                                         [KCET  2001]
  A)
             Dynamo                                  done clear
  B)
             generator done clear
  C)
             Electric motor                       done clear
  D)
             Induction coil done clear
  View Solution play_arrow

• question_answer29)
  An electric motor operates on a 50 volt supply and a current of 12A. If the efficiency of the motor is 30%, what is the resistance of the winding of the motor        [Kerala PET 2002]
  A)
             \[6\Omega \]                        done clear
  B)
             \[4\Omega \] done clear
  C)
             \[2.9\,\Omega \]                 done clear
  D)
             \[3.1\Omega \] done clear
  View Solution play_arrow

• question_answer30)
  A motor having an armature of resistance \[2\Omega \] is designed to operate at 220 V mains. At full speed, it develops a back e.m.f. of 210V. When the motor is running at full speed, the current in the armature is                                        [UPSEAT 2002]
  A)
             5A  done clear
  B)
             105A done clear
  C)
             110A                                         done clear
  D)
             215A done clear
  View Solution play_arrow

• question_answer31)
  Fan is based on                                                              [AFMC 2003]
  A)
             Electric Motor                       done clear
  B)
             Electric dynamo done clear
  C)
             Both                                         done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer32)
  A transformer is employed to [MP PET 1985; MP PMT 1993; RPET 1999]
  A)
             Obtain a suitable dc voltage done clear
  B)
             Convert dc into ac done clear
  C)
             Obtain a suitable ac voltage done clear
  D)
             Convert ac into dc done clear
  View Solution play_arrow

• question_answer33)
  What is increased in step-down transformer  [MP PMT/PET 1998; CPMT 1999]
  A)
             Voltage                                   done clear
  B)
              Current done clear
  C)
             Power                                      done clear
  D)
              Current density done clear
  View Solution play_arrow

• question_answer34)
  The core of a transformer is laminated so that [CPMT 1985; MP PMT 1994, 2000, 02, 03; BHU 1999]
  A)
             Ratio of voltage in the primary and secondary may be increased done clear
  B)
             Rusting of the core may be stopped done clear
  C)
             Energy losses due to eddy currents may be reduced done clear
  D)
             Change in flux is increased done clear
  View Solution play_arrow

• question_answer35)
  In transformer, core is made of soft iron to reduce [AIIMS 1998; UPSEAT 2001; AFMC 2005]
  A)
             Hysteresis losses done clear
  B)
             Eddy current losses done clear
  C)
             Force opposing electric current done clear
  D)
             None of the above done clear
  View Solution play_arrow

• question_answer36)
  The transformation ratio in the step-up transformer is
  A)
             1 done clear
  B)
             Greater than one done clear
  C)
             Less than one done clear
  D)
             The ratio greater or less than one depends on the other factors done clear
  View Solution play_arrow

• question_answer37)
  In a transformer 220 ac voltage is increased to 2200 volts. If the number of turns in the secondary are 2000, then the number of turns in the primary will be     [MP PET/PMT 1988]
  A)
             200 done clear
  B)
             100 done clear
  C)
             50   done clear
  D)
             20 done clear
  View Solution play_arrow

• question_answer38)
  The ratio of secondary to the primary turns in a transformer is 3 : 2. If the power output be P, then the input power neglecting all loses must be equal to [MP PMT 1984; KCET 2003]
  A)
             5 P  done clear
  B)
             1.5 P done clear
  C)
             P     done clear
  D)
             \[\frac{2}{5}P\] done clear
  View Solution play_arrow

• question_answer39)
  The primary winding of a transformer has 100 turns and its secondary winding has 200 turns. The primary is connected to an ac supply of 120 V and the current flowing in it is 10 A. The voltage and the current in the secondary are [MP PMT 1991; DPMT 2004]
  A)
             240 V, 5 A                               done clear
  B)
              240 V, 10 A done clear
  C)
             60 V, 20 A                               done clear
  D)
              120 V, 20 A done clear
  View Solution play_arrow

• question_answer40)
  A step-down transformer is connected to 2400 volts line and 80 amperes of current is found to flow in output load. The ratio of the turns in primary and secondary coil is 20 : 1. If transformer efficiency is 100%, then the current flowing in primary coil will be                                               [MP PMT 1991]
  A)
             1600 A                                      done clear
  B)
              20 A done clear
  C)
             4 A done clear
  D)
              1.5 A done clear
  View Solution play_arrow

• question_answer41)
  A loss free transformer has 500 turns on its primary winding and 2500 in secondary. The meters of the secondary indicate 200 volts at 8 amperes under these conditions. The voltage and current in the primary is              [MP PMT 1996]
  A)
             100 V, 16 A                             done clear
  B)
              40 V, 40 A done clear
  C)
             160 V, 10 A                             done clear
  D)
              80 V, 20 A done clear
  View Solution play_arrow

• question_answer42)
  An ideal transformer has 100 turns in the primary and 250 turns in the secondary. The peak value of the ac is 28 V. The r.m.s. secondary voltage is nearest to             [MP PMT 1992]
  A)
             50 V                                          done clear
  B)
             70 V done clear
  C)
             100 V                                        done clear
  D)
              40 V done clear
  View Solution play_arrow

• question_answer43)
  A transformer is employed to reduce 220 V to 11 V. The primary draws a current of 5 A and the secondary 90 A. The efficiency of the transformer is                                                                 [MP PMT 1992, 2001, 04]
  A)
             20%                                           done clear
  B)
              40% done clear
  C)
             70%                                           done clear
  D)
              90% done clear
  View Solution play_arrow

• question_answer44)
  In a step-up transformer, the turn ratio is 1 : 2. A Leclanche cell (e.m.f. 1.5V) is connected across the primary. The voltage developed in the secondary would be  [MP PET 1992, 99; AIIMS 2000; MP PMT 2000; RPET 2001]
  A)
             3.0 V                                         done clear
  B)
             0.75 V done clear
  C)
             1.5 V                                         done clear
  D)
             Zero done clear
  View Solution play_arrow

• question_answer45)
  The alternating voltage induced in the secondary coil of a transformer is mainly due to   [MP PET 1992; MP PMT 1996]
  A)
             A varying electric field done clear
  B)
             A varying magnetic field done clear
  C)
             The vibrations of the primary coil done clear
  D)
             The iron core of the transformer done clear
  View Solution play_arrow

• question_answer46)
  We can reduce eddy currents in the core of transformer  [MP PET 1993]
  A)
             By increasing the number of turns in secondary coil done clear
  B)
             By taking laminated core done clear
  C)
             By making step-down transformer done clear
  D)
             By using a weak ac at high potential done clear
  View Solution play_arrow

• question_answer47)
  A 100% efficient transformer has 100 turns in the primary and 25 turns in its secondary coil. If the current in the secondary coil is 4 amp, then the current in the primary coil is                                                     [MP PMT 1990]
  A)
             1 amp                                      done clear
  B)
             4 amp done clear
  C)
             8 amp                                      done clear
  D)
             16 amp done clear
  View Solution play_arrow

• question_answer48)
  The efficiency of transformer is very high because [MP PET 1994]
  A)
             There is no moving part in a transformer done clear
  B)
             It produces very high voltage done clear
  C)
             It produces very low voltage done clear
  D)
             None of the above done clear
  View Solution play_arrow

• question_answer49)
  In a lossless transformer an alternating current of  2 amp is flowing in the primary coil. The number of turns in the primary and secondary coils are 100 and 20 respectively. The value of the current in the secondary coil is [MP PMT 1994]
  A)
             0.08 A                                       done clear
  B)
             0.4 A done clear
  C)
             5 A done clear
  D)
             10 A done clear
  View Solution play_arrow

• question_answer50)
  A transformer connected to 220 volt line shows an output of 2 A at 11000 volt. The efficiency is 100%. The current drawn from the line is                                             [MP PMT 1995]
  A)
             100 A                                        done clear
  B)
             200 A done clear
  C)
             22 A                                          done clear
  D)
             11 A done clear
  View Solution play_arrow

• question_answer51)
  The coils of a step down transformer have 500 and 5000 turns. In the primary coil an ac of 4 ampere at 2200 volts is sent. The value of the current and potential difference in the secondary coil will be                                         [MP PET 1996]
  A)
             20 A, 220 V                             done clear
  B)
             0.4 A, 22000 V done clear
  C)
             40 A, 220 V                             done clear
  D)
             40 A, 22000 V done clear
  View Solution play_arrow

• question_answer52)
  A power transformer is used to step up an alternating e.m.f. of 220 V to 11 kV to transmit 4.4 kW of power. If the primary coil has 1000 turns, what is the current rating of the secondary ? Assume 100% efficiency for the transformer [MP PET 1997]
  A)
             4 A done clear
  B)
             0.4 A done clear
  C)
             0.04 A                                       done clear
  D)
             0.2 A done clear
  View Solution play_arrow

• question_answer53)
  A step up transformer connected to a 220 V AC line is to supply 22 kV for a neon sign in secondary circuit. In primary circuit a fuse wire is connected which is to blow when the current in the secondary circuit exceeds 10 mA. The turn ratio of the transformer is                                      [MP PET 1997]
  A)
             50   done clear
  B)
              100 done clear
  C)
             150 done clear
  D)
              200 done clear
  View Solution play_arrow

• question_answer54)
  In a transformer the primary has 500 turns and secondary has 50 turns. 100 volts are applied to the primary coil, the voltage developed in the secondary will be  [MP PMT 1997]
  A)
             1 V done clear
  B)
             10 V done clear
  C)
             1000 V                                      done clear
  D)
             10000 V done clear
  View Solution play_arrow

• question_answer55)
  A transformer is used to                                          [MP PET 1999]
  A)
             Change the alternating potential done clear
  B)
             Change the alternating current done clear
  C)
             To prevent the power loss in alternating current flow  done clear
  D)
             To increase the power of current source done clear
  View Solution play_arrow

• question_answer56)
  A step-up transformer operates on a 230 V line and supplies a load of 2 ampere. The ratio of the primary and secondary windings is 1 : 25. The current in the primary is [CBSE PMT 1998]
  A)
             15 A                                          done clear
  B)
             50 A done clear
  C)
             25 A                                          done clear
  D)
             12.5 A done clear
  View Solution play_arrow

• question_answer57)
  The number of turns in the primary coil of a transformer is 200 and the number of turns in the secondary coil is 10. If 240 volt AC is applied to the primary, the output from the secondary will be        [BHU 1997; JIPMER 2000]
  A)
             48 V                                          done clear
  B)
             24 V done clear
  C)
             12 V                                          done clear
  D)
             6 V done clear
  View Solution play_arrow

• question_answer58)
  The primary winding of transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of 20 V, 50 Hz. The secondary will have an output of              [CBSE PMT 1997; AIIMS 1999]
  A)
             200 V, 50 Hz                           done clear
  B)
             2 V, 50 Hz done clear
  C)
             200 V, 500 Hz                         done clear
  D)
             2 V, 5 Hz done clear
  View Solution play_arrow

• question_answer59)
  A step-up transformer has transformation ratio of 3 : 2. What is the voltage in secondary if voltage in primary is 30 V                                                                         [BHU 1998; Pb. PMT 2004]
  A)
             45 V                                          done clear
  B)
             15 V done clear
  C)
             90 V                                          done clear
  D)
             300 V done clear
  View Solution play_arrow

• question_answer60)
  In a transformer, the number of turns in primary coil and secondary coil are 5 and 4 respectively. If 240 V is applied on the primary coil, then the ratio of current in primary and secondary coil is             [AFMC 1998; CPMT 2000; Pb. PET 2002]
  A)
             4 : 5                                           done clear
  B)
             5 : 4 done clear
  C)
             5 : 9                                           done clear
  D)
             9 : 5 done clear
  View Solution play_arrow

• question_answer61)
  A step-down transformer is connected to main supply 200V to operate a 6V, 30W bulb. The current in primary is [AMU (Engg.) 1999]
  A)
             3 A done clear
  B)
             1.5 A done clear
  C)
             0.3 A                                         done clear
  D)
             0.15 A done clear
  View Solution play_arrow

• question_answer62)
  The number of turns in primary and secondary coils of a transformer are 100 and 20 respectively. If an alternating potential of 200 volt is applied to the primary, the induced potential in secondary will be                                              [RPET 1999]
  A)
             10 V                                          done clear
  B)
             40 V done clear
  C)
             1000 V                                      done clear
  D)
             20,000 V done clear
  View Solution play_arrow

• question_answer63)
  The ratio of secondary to primary turns is \[9:4.\] If power input is P, what will be the ratio of power output (neglect all losses) to power input                                              [DCE 1999]
  A)
             4 : 9                                           done clear
  B)
             9 : 4 done clear
  C)
             5 : 4                                           done clear
  D)
             1 : 1 done clear
  View Solution play_arrow

• question_answer64)
  Voltage in the secondary coil of a transformer does not depend upon.                                   [BHU 2000]
  A)
             Voltage in the primary coil done clear
  B)
             Ratio of number of turns in the two coils done clear
  C)
             Frequency of the source done clear
  D)
             Both (a) and (b) done clear
  View Solution play_arrow

• question_answer65)
   A transformer has turn ratio 100/1. If secondary coil has 4 amp current then current in primary coil is [RPET 2000]
  A)
             4 A done clear
  B)
             0.04 A done clear
  C)
             0.4 A                                         done clear
  D)
             400 A done clear
  View Solution play_arrow

• question_answer66)
  In a step-up transformer the turn ratio is 1:10. A resistance of 200 ohm connected across the secondary is drawing a current of 0.5 A. What is the primary voltage and current [MP PET 2000]
  A)
             50 V, 1 amp                           done clear
  B)
             10 V, 5 amp done clear
  C)
             25 V, 4 amp                           done clear
  D)
             20 V, 2 amp done clear
  View Solution play_arrow

• question_answer67)
  Large transformers, when used for some time, become hot and are cooled by circulating oil. The heating of transformer is due to                                                     [MP PET 2001]
  A)
             Heating effect of current alone done clear
  B)
             Hysteresis loss alone done clear
  C)
             Both the hysteresis loss and heating effect of current done clear
  D)
             None of the above done clear
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• question_answer68)
  In a step-up transformer the voltage in the primary is 220 V and the current is 5A. The secondary voltage is found to be 22000V. The current in the secondary (neglect losses) is    [Kerala PMT 2002]
  A)
             5 A done clear
  B)
             50 A done clear
  C)
             500 A                                        done clear
  D)
             0.05 A done clear
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• question_answer69)
  In a transformer, number of turns in the primary are 140 and that in the secondary are 280. If current in primary is 4A then that in the secondary is            [AIEEE 2002]
  A)
             4 A done clear
  B)
             2 A done clear
  C)
             6 A done clear
  D)
                  10 A done clear
  View Solution play_arrow

• question_answer70)
  A transformer has 100 turns in the primary coil and carries 8 A current. If input power is one kilowatt, the number of turns required in the secondary coil to have 500V output will be [MP PET 2002]
  A)
             100 done clear
  B)
             200 done clear
  C)
             400 done clear
  D)
             300 done clear
  View Solution play_arrow

• question_answer71)
     An ideal transformer has 500 and 5000 turn in primary and secondary windings respectively. If the primary voltage is connected to a 6V battery then the secondary voltage is  [Orissa JEE 2003]
  A)
             0     done clear
  B)
             60 V done clear
  C)
             0.6 V                                         done clear
  D)
             6.0 V done clear
  View Solution play_arrow

• question_answer72)
  In a primary coil 5A current is flowing on 220 volts. In the secondary coil 2200V voltage produces. Then ratio of number of turns in secondary coil and primary coil will be [RPET 2003]
  A)
             1 : 10                                         done clear
  B)
             10 : 1 done clear
  C)
             1 : 1                                           done clear
  D)
             11 : 1 done clear
  View Solution play_arrow

• question_answer73)
  A step up transformer has transformation ration 5 : 3. What is voltage in secondary if voltage in primary is 60 V [Pb. PET 2000]
  A)
             20 V                                          done clear
  B)
             60 V done clear
  C)
             100 V                                        done clear
  D)
             180 V done clear
  View Solution play_arrow

• question_answer74)
  In a step up transformer, 220 V is converted into 200 V. The number of turns in primary coil is 600. What is the number of turns in the secondary coil                                      [DCE 2004]
  A)
             60   done clear
  B)
             600 done clear
  C)
             6000                                          done clear
  D)
             100 done clear
  View Solution play_arrow

• question_answer75)
  The output voltage of a transformer connected to 220 volt line is 1100 volt at 1 amp current. Its efficiency is 100%. The current coming from the line is                             [Pb. PET 2003]
  A)
             20 A                                          done clear
  B)
             10 A done clear
  C)
             11 A                                          done clear
  D)
             22 A done clear
  View Solution play_arrow

• question_answer76)
  Quantity that remains unchanged in a transformer is  [MP PMT/PET 1998; AIIMS 1999; J & K CET 2005]
  A)
             Voltage                                   done clear
  B)
             Current done clear
  C)
             Frequency                             done clear
  D)
             None of the above done clear
  View Solution play_arrow

• question_answer77)
  In a region of uniform magnetic induction \[B={{10}^{-2}}\,tesla\], a circular coil of radius 30 cm and resistance p2 ohm is rotated about an axis which is perpendicular to the direction of B and which forms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating current induced in the coil is                                               [CBSE PMT 1990]
  A)
             4p2 mA                                    done clear
  B)
             30 mA done clear
  C)
             6 mA                                         done clear
  D)
             200 mA done clear
  View Solution play_arrow

• question_answer78)
  In a transformer, the number of turns in primary and secondary are 500 and 2000 respectively. If current in primary is 48 A, the current in the secondary is  [Orissa PMT 2004]
  A)
             12 A                                          done clear
  B)
             24 A done clear
  C)
             48 A                                          done clear
  D)
             144 A done clear
  View Solution play_arrow

• question_answer79)
  In an inductor of inductance L = 100 mH, a current of \[I=10A\] is flowing. The energy stored in the inductor is [Orissa PMT 2004]
  A)
             5 J   done clear
  B)
             10 J done clear
  C)
             100 J                                         done clear
  D)
             1000 J done clear
  View Solution play_arrow

• question_answer80)
  The turn ratio of a transformers is given as 2 : 3. If the current through the primary coil is 3 A, thus calculate the current through load resistance                      [BHU 2005]
  A)
             1 A done clear
  B)
             4.5 A done clear
  C)
             2 A done clear
  D)
             1. 5 A done clear
  View Solution play_arrow

• question_answer81)
  Core of transformer is made up of                                                           [AFMC 2005]
  A)
             Soft iron                                  done clear
  B)
             Steel done clear
  C)
             Iron                                           done clear
  D)
             Alnico done clear
  View Solution play_arrow

• question_answer82)
  The induction coil works on the principle of        [KCET 2005]
  A)
             Self-induction                       done clear
  B)
             Mutual induction done clear
  C)
             Ampere's rule                      done clear
  D)
             Fleming's right hand rule done clear
  View Solution play_arrow

• question_answer83)
  A transformer with efficiency 80% works at 4 kW and 100 V. If the secondary voltage is 200 V, then the primary and secondary currents are respectively            [Kerala PMT 2005]
  A)
             40 A, 16 A                               done clear
  B)
             16 A, 40 A done clear
  C)
             20 A, 40 A                               done clear
  D)
             40 A, 20 A done clear
  View Solution play_arrow

• question_answer84)
  In a step up transformer, if ratio of turns of primary to secondary is 1 : 10 and primary voltage is 230 V. If the load current is 2A, then the current in primary is [Orissa PMT 2005]
  A)
             20 A                                          done clear
  B)
             10 A done clear
  C)
             2 A done clear
  D)
             1 A done clear
  View Solution play_arrow

• question_answer85)
  If a coil made of conducting wires is rotated between poles pieces of the permanent magnet. The motion will generate a current and this device is called                           [CPMT 2005]
  A)
             An electric motor                done clear
  B)
             An electric generator        done clear
  C)
             An electromagnet              done clear
  D)
             All of above done clear
  View Solution play_arrow

• question_answer86)
  A step-down transformer is used on a 1000 V line to deliver 20 A at 120 V at the secondary coil. If the efficiency of the transformer is 80% the current drawn from the line is  [Kerala PET 2005]
  A)
             3 A done clear
  B)
             30 A                                          done clear
  C)
             0.3 A                                         done clear
  D)
             2.4 A done clear
  View Solution play_arrow