Q.1
A 50 mH coil carries a current of 4 amp. The energy stored un joules is [ MPPMT 1999]
  • a) 0.4 J
  • b) 4.0 J
  • c) 0.8 J
  • d) 0.04J
Q.2
a magnet is moving with fast speed towards the coil at rest. Due to this, the induced electromotive force, the induced current and the induced charge in the coil are E, I and Q respectively. If the speed of the magnet is doubled, the incorrect statement is [ MPPMT 1995]
  • a) E increases
  • b) I increases
  • c) Q remains constant
  • d) Q increases
Q.3
The north pole of a magnet is brought near a metallic ring as shown in the figure. The direction of induced current in the ring will be [ MPPMT 1998]
ch-18_que_no-101_img_no1.png
  • a) Anticlock wise
  • b) clock wise
  • c) First anti clock wise and then clockwise
  • d) First clock wise and then anticlockwise
Q.4
The current in a self inductance L = 40 mH is to be increased uniformly from 1A to 11A in 4 milliseconds. The emf induced in inductor during the process is [ CBSE 1990]
  • a) 100volts
  • b) 0.4 volts
  • c) 40 volts
  • d) 440 volts
Q.5
power is transmitted from a power house on high voltage a.c. because [ Raj.PMT 1997]
  • a) electric current travels faster at higher voltage
  • b) it is more economical due to less power wastage
  • c) it is difficult to generate power at low voltage
  • d) chances of stealing transmission lines are minimized
Q.6
Faraday's law of electromagnetic induction is [ CBSE 1993]
  • a) related to law of conservation of charge
  • b) related to law of conservation of energy
  • c) related to third law of Newton
  • d) related to law of conservation of angular momentum
Q.7
The bob of simple pendulum is replaced by a magnet. The oscillations are set along the length of the magnet. A copper coil is added so that one pole of the magnet passes in and out of coil. The coil is short-circuited. Then which one of the following happens? [ CET 1994]
  • a) Period decreases
  • b) Period does not change
  • c) Oscillations are damped
  • d) Amplitude increases
Q.8
Eddy current is produced in a material when it is [ CBSE 1993]
  • a) heated
  • b) Placed in time varying magnetic field
  • c) placed iin an electric field
  • d) placed in a uniform magnetic field
Q.9
L, C, R represents the physical quantities inductance, capacitance and resistance respectively. The combination which have the dimensions of frequency are [ BIT 1992]
  • a) 1 / RC
  • b) RL / C
  • c) R / LC
  • d) C /L
Q.10
A wire coil carries the current i, The potential energy of the coil does not depend upon [ MPPMT 1993]
  • a) the value of i
  • b) the number of turns in the coil
  • c) whether the coil has an iron core or not
  • d) the resistance of coil
Q.11
A long horizontal metallic rod with length along the east-west direction is falling under gravity. The potential difference between its ends will [ MPPMT 1997]
  • a) be zero
  • b) be constant
  • c) increase with time
  • d) decrease with time
Q.12
The coil of a dynamo is rotating in a magnetic field. The developed induced emf changes and the number of magnetic lines of force also changes. Which of the following conditions is correct? [ MPPET 1993]
  • a) lines of force minimum but induced emf is zero
  • b) lines of force maximum but induced emf is zero
  • c) lines of force maximum but induced emf is not zero
  • d) lines of force maximum but induced emf is also maximum
Q.13
Not to develop eddy currents in the core of the transformer [ MPPMT 1993]
  • a) By increasing the number of turns in secondary coil
  • b) By taking laminated core
  • c) By making step-down transformer
  • d) By using a weak-alternating current at hi high potential
Q.14
In an induction coil, the secondary emf is [ CET 1994]
  • a) zero during break of circuit
  • b) very high during make of the circuit
  • c) zero during make of the circuit
  • d) very high during break of the circuit
Q.15
When the current in a coil changes from 2 amp to 4 amp. in 0.05 sec. an emf of 8 volt is induced in the coil. The coefficient of self induction of the coil is [ MNR 1993]
  • a) 0.1 henry
  • b) 0.2 henry
  • c) 0.4 henry
  • d) 0.8 henry
Q.16
In a step up transformer the ratio of turns in secondary and primary coil is 4:If the current in primary is 4A, the current in secondary will be [ Raj.PMT 1996]
  • a) 8A
  • b) 2A
  • c) 1A
  • d) 0.5A
Q.17
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 [ MPPMT 1997]
  • a) 1 V
  • b) 10 V
  • c) 1000 V
  • d) 10,000 V
Q.18
A two metre wire is moving with velocity of 1 m/ sec perpendicular to a magnetic field of 0.5 weber/mThe emf induced in it will be [ MPPMT 1998]
  • a) 0.5 volt
  • b) 0.1 volt
  • c) 1 volt
  • d) 2 volt
Q.19
The inductance of coil is 60µH. A current in this coil increases from 1.0A to 1.5A in 0.1 second. The magnitude of the induced emf is [ PMT 1995]
  • a) 60×10⁻⁶ V
  • b) 300×10⁻⁴ V
  • c) 30×10⁻⁴
  • d) 3×10⁻⁴ V
Q.20
The number of turns in the primary and the secondary of a transformer are Np and Ns respectively. The resistance of the secondary circuit is Rs. From the point of view of the primary circuit, the equivalent resistance of the load is [ MPPMT 1997]
  • a)
    ch-18_qn-120choice_img_no1.png
  • b)
    ch-18_qn-120choice_img_no2.png
  • c)
    ch-18_qn-120choice_img_no3.png
  • d)
    ch-18_qn-120choice_img_no4.png
Q.21
The self-inductance of an induction coil is 5H. If the current in the primary changes from 5 A to zero in 10-3 sec time, the induced emf in the secondary coil will be [ Raj.PET 1996]
  • a) 2500 V
  • b) 25,000 V
  • c) 2510 V
  • d) zero
Q.22
The efficiency of transformer is very high because [ MPPMT 1994]
  • a) there is no moving parts in transformer
  • b) it produces very high voltage
  • c) it produces very low voltage
  • d) none of the above
Q.23
A light bulb, a capacitor and battery are connected together. When the switch is closed, which of the following is true
  • a) the bulb will light up from an instant when the capacitor starts charging
  • b) the bulb will light up when the capacitor is fully charged
  • c) the bulb will not light up at all
  • d) the bulb will light up and go off at regular intervals
Q.24
A varying current in a coil changes from 10 amp to zero in 0.5 sec. If the average emf induced in the coil is 220 volts, the self inductance of coil is [ EAMCET 19994]
  • a) 5 H
  • b) 10 H
  • c) 11 H
  • d) 12 H
Q.25
A coil of area 80 square cm and 50 turns is rotating with 2,000 revolutions per minute about an axis perpendicular to a magnetic field of 0.05 tesla. The maximum value of the emf developed in it is [ MPPMT 1994]
  • a) 200π volt
  • b) 10π/ 3 volt
  • c) 2π/3 volt
  • d) 2/3 volt
Q.26
The device that does not work on the principle of mutual induction us [ CET 1994]
  • a) induction coil
  • b) motor
  • c) tesala coil
  • d) transformer
Q.27
A 50 turn circular coil has a radius of 3cm it is kept in a magnetic field acting normal to the area of the coil. The magnetic field B is increased from 0.1 tesla to 0.35 tesla in 2 milli-seconds. The average induced emf in the coil is [ MPPMT 1994]
  • a) 1.77 volts
  • b) 17.7 volts
  • c) 177 volts
  • d) 0.177 volts
Q.28
The total charge induced in a conductor circuit moving in a magnetic field depends upon .. [ ISM Dhanba 1994]
  • a) the rate of change of magnetic flux linked with it
  • b) the total change of flux through it
  • c) the final magnetic flux
  • d) the number of lines of force initially linked with the circuit
Q.29
Two long parallel metallic wires with a resistance R form a horizontal plane. A conducting rod AB is on the wire as shown here. The space has a magnetic field pointing vertically upwards. The rod is given an initial velocity vo. There is no friction and no resistance in the wires and the rod. After a time t the velocity of the rod will be v such that [ PMT 1995]
ch-18_que_no-129_img_no1.png
  • a) v > vo
  • b) v < vo
  • c) v = vo
  • d) v = -vo
Q.30
If magnetic mono pole existed which of the following Maxwell's equation would be modified [ AMU 1995]
  • a)
    ch-18_qn-130choice_img_no1.png
  • b)
    ch-18_qn-130choice_img_no2.png
  • c)
    ch-18_qn-130choice_img_no3.png
  • d)
    ch-18_qn-130choice_img_no4.png
0 h : 0 m : 1 s