Q.1 Who discovered the phenomenon of electromagnetic induction?
James Clerk Maxwell
Michael Faraday
André-Marie Ampère
Heinrich Hertz
Explanation - Michael Faraday discovered electromagnetic induction in 1831, showing that a changing magnetic field can induce an electric current.
Correct answer is: Michael Faraday
Q.2 According to Faraday’s law, the induced emf is proportional to:
Rate of change of electric field
Rate of change of magnetic flux
Rate of change of resistance
Rate of current
Explanation - Faraday’s law states that induced emf is equal to the negative rate of change of magnetic flux through a coil.
Correct answer is: Rate of change of magnetic flux
Q.3 What is the SI unit of magnetic flux?
Tesla
Weber
Henry
Volt
Explanation - Magnetic flux is measured in Weber (Wb), defined as Tesla·m².
Correct answer is: Weber
Q.4 Lenz’s law gives the direction of:
Induced emf
Magnetic field
Electric field
Charge flow
Explanation - Lenz’s law states that the induced emf always opposes the change in magnetic flux that produced it, determining its direction.
Correct answer is: Induced emf
Q.5 Which of the following is NOT true about induced current?
It opposes the cause producing it
It depends on rate of change of flux
It follows Ohm’s law
It can exist without a magnetic field
Explanation - Induced current is always linked to a changing magnetic field; it cannot exist without it.
Correct answer is: It can exist without a magnetic field
Q.6 In a transformer, the principle of operation is:
Electrostatics
Electromagnetic induction
Photoelectric effect
Superconductivity
Explanation - Transformers work on electromagnetic induction by transferring energy between two coils via changing magnetic flux.
Correct answer is: Electromagnetic induction
Q.7 Self-induction is a phenomenon where:
A coil induces emf in a nearby coil
A coil induces emf in itself
A magnet induces emf in a coil
No emf is produced
Explanation - Self-induction occurs when the changing current in a coil induces emf in the same coil.
Correct answer is: A coil induces emf in itself
Q.8 Mutual induction occurs when:
Two magnets repel each other
Two coils induce emf in each other
A single coil produces emf
Electric current opposes voltage
Explanation - Mutual induction is the process by which a change in current in one coil induces emf in a nearby coil.
Correct answer is: Two coils induce emf in each other
Q.9 The SI unit of inductance is:
Henry
Weber
Tesla
Volt
Explanation - Inductance is measured in Henry (H), defined as Weber per Ampere.
Correct answer is: Henry
Q.10 Which device works purely on the principle of electromagnetic induction?
Electric heater
Electric motor
Generator
Capacitor
Explanation - A generator converts mechanical energy into electrical energy using electromagnetic induction.
Correct answer is: Generator
Q.11 Eddy currents are:
Currents in wires
Localized circular currents in conductors
Currents in capacitors
High-frequency AC currents
Explanation - Eddy currents are circular currents induced within conductors due to changing magnetic flux.
Correct answer is: Localized circular currents in conductors
Q.12 What minimizes eddy currents in transformer cores?
Solid cores
Laminated cores
Plastic cores
Air gaps
Explanation - Transformer cores are laminated to reduce eddy currents and energy loss.
Correct answer is: Laminated cores
Q.13 The energy stored in an inductor is:
½ LI²
½ CV²
IR
VI
Explanation - The magnetic energy stored in an inductor is given by E = ½ LI².
Correct answer is: ½ LI²
Q.14 A changing magnetic flux through a coil induces:
Charge only
Resistance only
Voltage only
Voltage and current
Explanation - A changing magnetic flux induces emf (voltage) and, if a closed path is present, current.
Correct answer is: Voltage and current
Q.15 Which law explains conservation of energy in electromagnetic induction?
Ohm’s law
Lenz’s law
Coulomb’s law
Ampere’s law
Explanation - Lenz’s law ensures induced emf opposes change, preserving energy conservation.
Correct answer is: Lenz’s law
Q.16 An AC generator produces alternating emf because:
Commutator reverses current
Slip rings maintain coil rotation
Magnetic flux continuously changes
Current is rectified
Explanation - AC generators use rotating coils in magnetic fields, producing continuously changing flux and alternating emf.
Correct answer is: Magnetic flux continuously changes
Q.17 If the number of turns in a coil is doubled, the induced emf will:
Halve
Remain same
Double
Quadruple
Explanation - Induced emf is proportional to the number of turns; doubling turns doubles emf.
Correct answer is: Double
Q.18 What is the unit of self-inductance?
Weber/Ampere
Tesla
Volt
Ampere
Explanation - Self-inductance is measured in Weber per Ampere, equivalent to Henry.
Correct answer is: Weber/Ampere
Q.19 The induced emf in a coil depends on:
Area of the coil
Number of turns
Rate of change of magnetic flux
All of these
Explanation - Induced emf is proportional to rate of change of flux, coil area, and number of turns.
Correct answer is: All of these
Q.20 If flux through a coil decreases, induced emf acts:
To increase flux
To decrease flux
To keep flux constant
Randomly
Explanation - According to Lenz’s law, emf acts to oppose the decrease by increasing flux.
Correct answer is: To increase flux
Q.21 The emf induced in a straight conductor moving in a magnetic field depends on:
Length of conductor
Velocity of conductor
Magnetic field strength
All of these
Explanation - Induced emf = B × l × v, depending on magnetic field, length, and velocity.
Correct answer is: All of these
Q.22 In induction heating, energy is dissipated mainly due to:
Resistance heating
Eddy currents
Capacitance
Self-inductance
Explanation - Induction heating is caused by eddy currents generated in conductive materials.
Correct answer is: Eddy currents
Q.23 A choke coil is used in AC circuits to:
Decrease voltage
Increase current
Limit current
Convert AC to DC
Explanation - Choke coils use self-inductance to limit AC current without power loss.
Correct answer is: Limit current
Q.24 Faraday’s law is mathematically expressed as:
emf = dΦ/dt
emf = -dΦ/dt
emf = L × I
emf = IR
Explanation - Faraday’s law: emf induced = negative rate of change of magnetic flux.
Correct answer is: emf = -dΦ/dt
Q.25 In DC, inductors behave as:
Open circuits
Closed circuits
Capacitors
Resistors
Explanation - In steady DC, inductors allow constant current like a short circuit.
Correct answer is: Closed circuits