83 free MCQs on Electromagnetic Induction, each with its own worked answer and explanation. Faraday's and Lenz's laws, motional EMF, self/mutual inductance, eddy currents, and the AC generator - how a changing magnetic flux creates an electric current.
Take the timed Electromagnetic Induction chapterwise test →83 practice questions on Electromagnetic Induction, sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Electromagnetic Induction notes.
As a magnet approaches a coil, flux rises steadily and a constant non-zero EMF is induced (Faraday's law). Once the magnet stops moving, flux stays constant and the induced EMF drops to zero - EMF only exists while flux is actively changing.
Q1.
A coil of resistance 2 Ω has 50 turns. The magnetic flux through each turn changes by 0.004 Wb. The total charge that flows through the coil is:
Q2.
An ideal transformer has 1000 turns in its primary and 5000 turns in its secondary. If the secondary current is 2 A, the primary current is:
Q3.
In an AC generator, the function of slip rings is to:
Q4.
Eddy currents are deliberately used in an induction furnace mainly to:
Q5.
Faraday's law of electromagnetic induction states that induced EMF is proportional to:
Q6.
Lenz's law is a consequence of:
Q7.
Electromagnetic induction was discovered by:
Q8.
Mutual inductance is the property due to which change in current in one coil:
Q9.
Self-inductance of a coil depends on:
Q10.
Magnetic flux is defined as:
Q12.
An induced EMF is generated in a coil whenever there is a change in:
Q13.
A device that converts mechanical energy into electrical energy using the principle of electromagnetic induction is called a:
Q14.
The direction of an induced current, as given by Lenz's law, is such that it:
Q15.
Electromagnetic induction is the production of an EMF by a changing:
Q16.
Electromagnetic induction was discovered by:
Q17.
The induced EMF always opposes the change that produces it. This is:
Q19.
A current produced by a changing magnetic field is called an:
Q20.
Moving a magnet toward a coil ___ an EMF in the coil:
Q22.
A device that uses electromagnetic induction to generate electricity is the:
Q23.
A transformer works on the principle of:
Q24.
The faster the magnetic flux through a coil changes, the ___ the induced EMF:
Q25.
The current through a 0.5 H inductor changes steadily from 2 A to 6 A in 0.1 s. The magnitude of the self-induced emf is:
Q26.
A conducting rod of length 0.5 m moves at 4 m/s perpendicular to a magnetic field of 0.8 T on rails connected by a 2 Ω resistor. The magnetic force opposing the motion is:
Q27.
A generator coil has a peak emf of 20 V. At an instant when the magnetic flux through the coil is half its maximum value, the magnitude of the induced emf is:
Q28.
A transformer changes 220 V to 1100 V. The secondary current is 2 A and the transformer operates with 80% efficiency. The primary current is:
Q29.
The magnetic flux through a 50-turn coil varies as Φ = 0.02 sin(100t) Wb. The peak induced emf is:
Q30.
A rectangular conducting loop of resistance 4 Ω moves completely out of a uniform magnetic field. If the total change in flux per turn is 0.08 Wb and the loop has 20 turns, the total charge passing through the loop is:
Q31.
Induced EMF in a loop rotating in magnetic field at angular velocity omega (area A, field B):
Q32.
EMF induced in a straight conductor of length L moving at velocity v perpendicular to field B:
Q33.
In an AC generator, the frequency of induced EMF depends on:
Q34.
A coil of self-inductance 100 mH carries current changing at 10 A/s. Induced EMF:
Q35.
Energy stored in an inductor L carrying current I:
Q36.
When a bar magnet is moved toward a coil, induced current creates a:
Q37.
A copper ring is dropped from rest above a strong magnet, oriented so it falls coaxially toward the magnet's pole. Compared to a similar non-conducting ring dropped from the same height, the copper ring:
Q38.
Two coils, P and Q, are placed near each other. When the current in coil P changes at a rate of 5 A/s, an EMF of 0.02 V is induced in coil Q. The mutual inductance between the coils is:
Q39.
A conducting rod slides on two parallel rails in a region with a uniform magnetic field perpendicular to the plane of the rails, generating a motional EMF. If the rod's speed is doubled while the field and rod length remain unchanged, the induced EMF:
Q40.
A solenoid has self-inductance L. If the number of turns per unit length is doubled while keeping the same length and cross-sectional area, the self-inductance becomes:
Q41.
Faraday’s law states that the induced EMF equals the rate of change of:
Q42.
Lenz’s law is a direct consequence of the conservation of:
Q43.
The EMF induced in a rod of length L moving at speed v perpendicular to a field B is:
Q44.
Self-inductance of a coil opposes any change in its:
Q45.
A step-up transformer increases the:
Q46.
The energy stored in an inductor of inductance L carrying current I is:
Q47.
Eddy currents are induced currents that circulate in:
Q48.
For a coil of N turns, the induced EMF is −N times the rate of change of:
Q49.
A transformer operates only with ___ current:
Q50.
The mutual inductance between two coils depends on their:
Q51.
A generator has 200 turns, each of area 0.001 m<sup>2</sup>, and rotates at 50 Hz in a magnetic field of 0.5 T. Its coil resistance is 10 Ω and it is connected to a 10 Ω load. The power delivered to the load is approximately:
Q52.
An ideal transformer has a voltage ratio V<sub>p</sub>:V<sub>s</sub> = 10:1. A 44 Ω load is connected to the secondary. If the transformer efficiency is 90% and the primary voltage is 2200 V, the primary current is approximately:
Q53.
A conducting rod of length 0.5 m moves at 4 m/s perpendicular to a 0.8 T magnetic field. The circuit resistance is 2 Ω. The mechanical power required to maintain constant speed is:
Q54.
A coil of 100 turns and area 0.02 m<sup>2</sup> rotates at 50 Hz in a magnetic field of 0.3 T. The rms value of its induced emf is approximately:
Q55.
A transformer has 500 turns in its primary and 2000 turns in its secondary. The primary is connected to 100 V AC and the secondary supplies a 200 Ω load. If the transformer is ideal, the current drawn from the primary is:
Q56.
A rectangular loop of area 0.02 m² lies in a field B = 0.5 T with its normal at 30° to B. The magnetic flux through the loop is:
Q57.
A square coil (N=100, side 10 cm, R=10 ohm) rotates at 600 rpm in B=0.1 T. Peak induced EMF:
Q58.
Mutual inductance M of two coaxial solenoids (inner: n<sub>1</sub> turns/m, area A; outer: n<sub>2</sub> turns/m, length l):
Q59.
A conducting rod of length L rotates at angular velocity omega about one end in a perpendicular field B. EMF generated:
Q60.
Eddy currents in a transformer core are minimized by:
Q61.
A rectangular coil enters a uniform magnetic field region at constant velocity. During entry, the induced current:
Q62.
AC generator operates at 50 Hz. Coil has 200 turns, area 0.01 m<sup>2</sup> in field 0.5 T. Peak EMF:
Q63.
A metallic rod of length L rotates with angular velocity ω about a perpendicular axis through its centre (not through one end), in a uniform magnetic field B parallel to the axis. The potential difference between the two ends of the rod is:
Q64.
A long solenoid of cross-sectional area A and n turns per unit length carries a current that varies as I = I<sub>0</sub> sin(ωt). A small circular coil of N turns and area a (a << A) is placed coaxially inside the solenoid. The peak EMF induced in the small coil is:
Q65.
A metal disc rotates with angular velocity ω about an axis through its centre, perpendicular to its plane, in a uniform magnetic field B parallel to the axis (Faraday disc dynamo). The EMF induced between the centre and the rim of the disc (radius R) is:
Q66.
In an ideal transformer, the ratio of secondary to primary voltage equals:
Q67.
The direction of an induced current is found using:
Q68.
The self-inductance of a long solenoid is L = μ₀n²Al, where n is the number of turns per unit:
Q69.
In a step-down transformer, the number of secondary turns is ___ the number of primary turns:
Q70.
Eddy-current losses in a transformer core are reduced by using:
Q71.
A metal plate swinging between the poles of a magnet is quickly damped because of:
Q72.
The EMF induced in a coil rotating steadily in a uniform magnetic field is:
Q73.
In the relation ε₂ = −M(dI₁/dt) between two coils, the quantity M is the:
Q74.
An ideal transformer conserves ___, so that VpIp = VsIs:
Q75.
The unit henry is equivalent to:
Q76.
The magnetic flux through a coil changes by 0.2 Wb in 0.1 s. The average induced emf is:
Q77.
A conducting rod of length 0.2 m moves at 10 m/s perpendicular to a 0.5 T field. The motional emf induced is:
Q78.
The energy stored in an inductor of 2 H carrying a current of 3 A is:
Q79.
According to Lenz law, the induced current in a circuit always flows so as to:
Q80.
Two coils have mutual inductance 0.5 H. If the current in one changes at 4 A/s, the emf induced in the other is:
Q81.
A coil of 100 turns links a flux of 0.01 Wb per turn when it carries 2 A. Its self-inductance is:
Q82.
The peak emf of a coil rotating in a magnetic field is NBAω. If the angular speed ω is doubled, the peak emf:
Q83.
Eddy currents induced in a metal plate moving through a magnetic field primarily cause:
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