MCQs on Electromotive Force

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Electromotive force refers to electric potential produced by a changing magnetic field or an electrochemical cell. Electromotive force is measured in volts. The electromotive force is the amount of energy given to each coulomb of charge. The electromotive force is independent of the circuit's internal resistance.

Electromotive-Force-EMF

Electromotive-Force-EMF

The video below explains this:

Electromotive Force Detailed Video Explanation:

Ques 1: The average emf induced per turn in a transformer is given by

1.11f Φ_m
0.5f Φ_m
4f Φ_m
8f Φ_m

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Answer: The correct answer is (c) 4f Φ_m

Explanation: EMF Equation Of The Transformer

Let,

N1 = Number of turns in primary winding

N2 = Number of turns in secondary winding

Φm = Maximum flux in the core (in Wb) = (Bm x A)

f = frequency of the AC supply (in Hz)

The flux rises to its maximum value Φ_m from 0. It reaches the maximum value in one-quarter of the cycle i.e in T/4 sec. Here, T is the time period of the sin wave of the supply = 1/f). Thus, average rate of change of flux = ^Φ_m /_(T/4) = ^Φ_m /_(1/4f)

Therefore, average rate of change of flux = 4f Φ_m ....... (Wb/s).

Induced emf per turn = rate of change of flux per turn.

Therefore, average emf per turn = 4f Φ_m ..........(Volts).

Ques 2: The flux used in the equation for the calculation of induced emf in a transformer is in its

RMS value

Average value

Maximum value

Twice that of the maximum value

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Answer: The correct answer is (c) Maximum Value

Explanation: EMF equation of a transformer

E = 4.44fϕmN

Here

ϕm = Maximum flux
N = number of turns
f = frequency
E = EMF

Ques 3: In which device is the principle of statically induced emf used?

Transformer

Motor

Generator

Battery

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Answer: The correct answer is (b) Transformer

Explanation: In a transformer, the windings are stationary, the magnetic field induced moves around the conductor and produces the emf. Thus transformer uses the principle of statically induced emf among the available options.

Ques 4: Which is the property of a coil by which a counter emf is induced when the current through the coil changes?

Self-inductance

Mutual inductance

Capacitance

None of these

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Answer: The correct answer is (a) Self-inductance

Explanation: The property of the coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as self-inductance.

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Types of Resistors	Unit of Specific Resistance	Carbon Resistor

Ques 5: The principle of dynamically induced emf is used in a

Choke

Transformer

Generator

Thermo-couple

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Answer: The correct answer is (c) Generator

Explanation: Dynamic Induced emf is generated when a current carrying conductor cuts the magnetic flux using relative motion. It has rotating parts in it, inducing emf with respect to moving parts is known as dynamic Induced emf. The generator works on the production of dynamically generated e.m.f in the conductors.

Ques 6: Statically induced emf’s magnitude depends on the

Rate of change of flux

Coil resistance

Flux magnitude

None of these

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Answer: The correct answer is (a) Rate of change of flux

Explanation: Induced emf is directly proportional to the number of turns, magnetic field, area, and the time in which the magnetic flux changes. Thus, the magnitude of the induced emf depends on the change in magnetic flux and also on the time in which the magnetic flux changes.

Ques 7: Power of battery having emf E₁=20V is

44.2 Watt

30.8 Watt

13.4 Watt

20 Watt

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Answer: The correct answer is (a) 44.2 Watt

Explanation: Power of battery is

P_emf=iE

Power supplied by battery E₁ = I₁E₁=44.2 Watt

Ques 8: Whenever there is a change in magnetic flux with respect to an electric conductor or a coil, an EMF is induced in the conductor is Faraday’s

first law

third law

second law

fourth law

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Answer: The correct answer is (a) first law

Explanation: When a conductor cuts magnetic flux, an emf is induced in the conductor. Faraday's law of induction is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force.

Ques 9: Who introduced the right-hand rule for determining the direction of the induced EMF?

Fleming

Lenz

Maxwell

Faraday

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Answer: The correct answer is (a) Fleming

Explanation: Invented in the 19th century by British physicist John Ambrose Fleming for applications in electromagnetism, the right-hand rule is most often used to determine the direction of a third parameter when the other two are known (magnetic field, current, magnetic force).

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Ques 10: What should be the value of the primary to the secondary ratio for a transformer to be an isolation transformer?

Equal to one

Less than one

More than one

Equal to 0.5

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Answer: The correct answer is (a) Equal to one

Explanation: Transformers that have a ratio of 1 to 1 between the primary and secondary windings are often used to protect secondary circuits and individuals from electrical shocks between energized conductors and earth ground. Suitably designed isolation transformers block interference caused by ground loops.

Ques 11: If the electromotive force of the battery is 5 V, the total energy supplied by the battery is

2.5 joules

5 joules

1 joule

10 joules

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Answer: The correct answer is (b) 5 Joules

Explanation: The total energy supplied by the battery is 5 Joules. The electromotive force or EMF is the amount of energy supplied by a cell or a battery per coulomb of charge passing through it.

Ques 12: Electric potential and Electromotive force (EMF) are

different terms
have different units
same terms
undefined terms

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Answer: The correct answer is (c) same terms

Explanation: The terms potential difference and voltage are the same. The potential difference between point A and B is also known as the voltage between point A and point B.

Ques 13: Unit of electromotive force is

volt
second
metre
m s⁻¹

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Answer: The correct answer is (a) Volt

Explanation: It is commonly measured in units of volts, equivalent in the meter–kilogram–second system to one joule per coulomb of electric charge. In the electrostatic units of the centimeter–gram–second system, the unit of electromotive force is the statvolt or one erg per electrostatic unit of charge.

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MCQs on Electromotive Force

Electromotive Force Detailed Video Explanation:

CBSE CLASS XII Related Questions

1.
Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.

2.
A square loop of side 0.50 m is placed in a uniform magnetic field of 0.4 T perpendicular to the plane of the loop. The loop is rotated through an angle of 60° in 0.2 s. The value of emf induced in the loop will be:

3.
Four independent waves are expressed as \[ (i)\; y_1=A_1\sin\omega t, \] \[ (ii)\; y_2=A_2\sin 2\omega t, \] \[ (iii)\; y_3=A_3\cos\omega t, \] \[ (iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right) \] The interference between two of these waves is possible in

4.
Assertion (A) : All atoms have a net magnetic moment. Reason (R) : A current loop does not always behave as a magnetic dipole.

5.
Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.

6.
Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.

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MCQs on Electromotive Force

Electromotive Force Detailed Video Explanation:

CBSE CLASS XII Related Questions

1.Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.

2.A square loop of side 0.50 m is placed in a uniform magnetic field of 0.4 T perpendicular to the plane of the loop. The loop is rotated through an angle of 60° in 0.2 s. The value of emf induced in the loop will be:

3.Four independent waves are expressed as \[ (i)\; y_1=A_1\sin\omega t, \] \[ (ii)\; y_2=A_2\sin 2\omega t, \] \[ (iii)\; y_3=A_3\cos\omega t, \] \[ (iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right) \] The interference between two of these waves is possible in

4.Assertion (A) : All atoms have a net magnetic moment. Reason (R) : A current loop does not always behave as a magnetic dipole.

5. Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.

6.Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.

Comments

SUBSCRIBE TO OUR NEWS LETTER

1.
Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.

2.
A square loop of side 0.50 m is placed in a uniform magnetic field of 0.4 T perpendicular to the plane of the loop. The loop is rotated through an angle of 60° in 0.2 s. The value of emf induced in the loop will be:

3.
Four independent waves are expressed as \[ (i)\; y_1=A_1\sin\omega t, \] \[ (ii)\; y_2=A_2\sin 2\omega t, \] \[ (iii)\; y_3=A_3\cos\omega t, \] \[ (iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right) \] The interference between two of these waves is possible in

4.
Assertion (A) : All atoms have a net magnetic moment. Reason (R) : A current loop does not always behave as a magnetic dipole.

5.
Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.

6.
Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.