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Electromagnetic Induction Physics - Electromagnetic Induction

Rajasthan Board (RBSE) - STD 12 Science - Physics (Rajasthan - English Medium). 308 questions in this chapter.

Question types

Electromagnetic Induction question types

308 questions across 7 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

308
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7
Question groups
5
Question types
Sample Questions

Electromagnetic Induction questions

One sample from each question group in this chapter. Select any group above to see the full set with answer keys.

Q 1M.C.Q (1 Marks)1 Mark
A coil of area $80 cm^2$ and number of turns $50$ is rotating about an axis perpendicular to a magnetic field of $0.05$ Tesla at $2000$ rotations per minute. The maximum value of emf induced in it will be.
  • A
    $200\pi\text{ volt}$
  • B
    $\frac{10\pi}{3}\text{volt}$
  • ✓
    $\frac{4\pi}{3}\text{volt}$
  • D
    $\frac{2}{3}\text{volt}$

Answer: C.

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Q 2M.C.Q (1 Marks)1 Mark
The self-inductance of a long solenoid carrying current is independent of:
  • A
    its length
  • ✓
    the current
  • C
    its cross-sectional area
  • D
    magnetic permeability of the core

Answer: B.

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Q 3M.C.Q (1 Marks)1 Mark
When a coil of cross-sectional area A and number of turns $N$ is rotated in a uniform magnetic field $B$ with angular velocity $\omega$ then the maximum emf induced in the coil will be.
  • A
    $\text{BNA}$
  • B
    $\frac{\text{BA}\omega}{\text{N}}$
  • ✓
    $\text{BNA}\omega$
  • D
    $\text{zero}$

Answer: C.

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Q 5M.C.Q (1 Marks)1 Mark
Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be.
Image
  • ✓
    maximum in situation $(A)$
  • B
    maximum in situation $(B)$
  • C
    maximum in situation $(C)$
  • D
    the same in all situations

Answer: A.

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Q 6Assertion (A) & Reason (B) MCQ1 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): Inductance coil are made of copper.
Reason (R): Induced current is more in wire having less resistance.
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Q 7Assertion (A) & Reason (B) MCQ1 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): When number of turns in a coil doubled, coefficient of self inductance of the coil becomes four times.
Reason (R): Coefficient of self inductance is proportional to the square of number of turns.
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Q 8Assertion (A) & Reason (B) MCQ1 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): An artificial satellite with a metal surface is moving above the earth in a circular orbit. A current will be induced in satellite if the plane of the orbit is inclined to the plane of the equator.
Reason (R): The current will be induced only when the speed of satellite is more than 8km/ sec.
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Q 9Assertion (A) & Reason (B) MCQ1 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): An induced current is developed when the number of magnetic lines of force associated with conductor is changed.
Reason (R): An induced current develop in a conductor moved in a direction parallel to the magnetic field.
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Q 10Assertion (A) & Reason (B) MCQ1 Mark
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b ), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and Rare true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): Changing magnetic flux can produce induced e.m.f.
Reason (R): Faraday established induced e.m.f. experimentally.
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Q 111 Marks Question1 Mark
A long straight current carrying wire passes normally through the centre of circular loop. If the current through the wire increases, will there be an induced emf in the loop? Justify.
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Q 131 Marks Question1 Mark
A conducting loop is held below a current carrying wire PQ as shown. Predict the direction of the induced current in the loop when the current in the wire is constantly increasing.
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Q 141 Marks Question1 Mark
A bar magnet is moved in the direction indicated by the arrow between two coils PQ and CD. Predict the direction of the induced current in each coil.
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Q 151 Marks Question1 Mark
Define the term self-inductance of a solenoid. Obtain the expression for the magnetic energy stored in an inductor of self-inductance L to build up a current I through it.
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Q 162 Marks Questions2 Marks
A 1.0m long metallic rod is rotated with an angular frequency of 400 rad $s^{-1}$ about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field of 0.5T parallel to the axis exists everywhere. Calculate the emf developed between the centre and the ring.
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Q 182 Marks Questions2 Marks
Use Lenz’s law to determine the direction of induced current in the situations described by Fig.
  1. A wire of irregular shape turning into a circular shape;
  1. A circular loop being deformed into a narrow straight wire.
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Q 192 Marks Questions2 Marks
State the underlying principle of a transformer.How is the large scale transmission of electric energy over long distances done with the use of transformers?
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Q 213 Marks Question3 Marks
A horizontal straight wire 10m long extending from east to west is falling with a speed of $5.0ms^{–1}$, at right angles to the horizontal component of the earth’s magnetic field, $0.30 \times 10^{–4}Wbm^{–2}.$
  1. What is the instantaneous value of the emf induced in the wire?
  2. What is the direction of the emf?
  3. Which end of the wire is at the higher electrical potential?
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Q 223 Marks Question3 Marks
A rectangular wire loop of sides 8cm and 2cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is $1\ cms^{–1}$ in a direction normal to the:
  1. Longer side,
  2. shorter side of the loop?
For how long does the induced voltage last in each case?
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Q 233 Marks Question3 Marks
A line charge $\lambda$ per unit length is lodged uniformly onto the rim of a wheel of mass M and radius R. The wheel has light non-conducting spokes and is free to rotate without friction about its axis (Fig.). A uniform magnetic field extends over a circular region within the rim. It is given by,
$B = – B_0k (r ≤ a; a < R)$
= 0 (otherwise)
What is the angular velocity of the wheel after the field is suddenly switched off?
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Q 243 Marks Question3 Marks
A circular coil of radius 8.0cm and 20 turns is rotated about its vertical diameter with an angular speed of 50rad $s^{–1}$ in a uniform horizontal magnetic field of magnitude $3.0 \times 10^{–2}T.$ Obtain the maximum and average emf induced in the coil. If the coil forms a closed loop of resistance 10Ω, calculate the maximum value of current in the coil. Calculate the average power loss due to Joule heating. Where does this power come from?
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Q 253 Marks Question3 Marks
A pair of adjacent coils has a mutual inductance of 1.5H. If the current in one coil changes from 0 to 20A in 0.5s, what is the change of flux linkage with the other coil?
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Q 275 Marks Questions5 Marks
Figure shows a metal rod PQ resting on the smooth rails AB and positioned between the poles of a permanent magnet. The rails, the rod, and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15cm, B = 0.50T, resistance of the closed loop containing the rod = 9.0mΩ. Assume the field to be uniform.
  1. Suppose K is open and the rod is moved with a speed of $12cms^{-1}$ in the direction shown. Give the polarity and magnitude of the induced emf.
  1. Is there an excess charge built up at the ends of the rods when K is open? What if K is closed?
  2. With K open and the rod moving uniformly, there is no net force on the electrons in the rod PQ even though they do experience magnetic force due to the motion of the rod. Explain.
  3. What is the retarding force on the rod when K is closed?
  4. How much power is required (by an external agent) to keep the rod moving at the same speed $(= 12cms^{–1})$ when K is closed? How much power is required when K is open?\
  5. How much power is dissipated as heat in the closed circuit? What is the source of this power?
  6. What is the induced emf in the moving rod if the magnetic field is parallel to the rails instead of being perpendicular?
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Q 285 Marks Questions5 Marks
  1. Obtain an expression for the mutual inductance between a long straight wire and a square loop of side a as shown in Fig.
  2. Now assume that the straight wire carries a current of 50A and the loop is moved to the right with a constant velocity, v = 10\m/s. Calculate the induced emf in the loop at the instant when x = 0.2m. Take a = 0.1m and assume that the loop has a large resistance.
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Q 295 Marks Questions5 Marks
Suppose the loop in Exercise 6.4 is stationary but the current feeding the electromagnet that produces the magnetic field is gradually reduced so that the field decreases from its initial value of 0.3T at the rate of $0.02T s^{–1}.$ If the cut is joined and the loop has a resistance of 1.6Ω, how much power is dissipated by the loop as heat? What is the source of this power?
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Q 305 Marks Questions5 Marks
It is desired to measure the magnitude of field between the poles of a powerful loud speaker magnet. A small flat search coil of area $2cm^2$ with 25 closely wound turns, is positioned normal to the field direction, and then quickly snatched out of the field region. Equivalently, one can give it a quick 90º turn to bring its plane parallel to the field direction). The total charge flown in the coil (measured by a ballistic galvanometer connected to coil) is 7.5mC. The combined resistance of the coil and the galvanometer is 0.50Ω. Estimate the field strength of magnet.
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Q 31Case study (4 Marks)4 Marks
Sunita and her friends visited an exhibition. The policeman asked them to pass through a metal detector. Sunita’s friends were initially scared of it. Sunita, however, explained to them the purpose and working of the metal detector.
Answer the following questions:
  1. On what principle does a metal detector work?
  2. Why does the detector emit sound when a person carrying any metallic object walks through it?
  3. State any two qualities which Sunita displayed while explaining the purpose of walking through the detector.
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Q 32Case study (4 Marks)4 Marks
A conducting loop is held above a current carrying wire ‘PQ’ as shown in the figure. Depict the direction of the current induced in the loop when the current in the wire PQ is constantly increasing.
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Q 33Case study (4 Marks)4 Marks
Ram is a student of class X in a village school. His uncle gifted him a bicycle with a dynamo fitted in it. He was very excited to get it. While cycling during night, he could light the bulb and see the objects on the road. He however, did not know this device works. He asked this question to his teacher. the teacher considered it an opportunity to explain the working to the whole class.
Answer the following question:
  1. State the principle and working of a dynamo.
  2. Write two values each displayed by Ram and his school teacher.
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Q 35Case study (4 Marks)4 Marks
The emf induced across the ends of a conductor due to its motion in a magnetic field is called motional emf. It is produced due to the magnetic Lorentz force acting on the free electrons of the conductor. For a circuit shown in figure, if a conductor of length l moves with velocity v in a magnetic field B perpendicular to both its length and the direction of the magnetic field, then all the induced parametres are possible in the circuit.
  1. Direction of current induced in a wire moving in a magnetic field is found using
  1. Fleming's left hand rule.
  2. Fleming's right hand rule.
  3. Ampere's rule.
  4. Right hand clasp rule.
  1. A conducting rod of length l is moving in a transverse magnetic field of strength B with velocity v. The resistance of the rod is R. The current in the rod is:
  1. $\frac{\text{Blv}}{R}$
  2. $\frac{\text{B}^2\text{v}^2\text{l}^2}{\text{R}}$
  3. Blv
  4. Zero
  1. A 0.1m long conductor carrying a current of SO A is held perpendicular to a magnetic field of 1.25mT. The mechanical power required to move the conductor with a speed of I m $s^{-1}$​​​​​​​ is:
  1. 62.5 mW
  2. 625 mW
  3. 6.25 mW
  4. 12.5 mW
  1. A bicycle generator creates 1.5 Vat 15km/ hr. The EMF generated at 10km/ hr is:
  1. 1.5 volts
  2. 2 volts
  3. 0.5 volts
  4. 1 volt
  1. The dimensional formula for emf E in MKS system will be:
  1. $[ML^2T^{-3}A^{-1}]$
  2. $[ML^2T^{-1}A]$
  3. $[ML^2A]$
  4. $[MLT^-^3A^{-1}]$
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