Question 1

Which of the following best describes the principle behind the generation of lightning between clouds and the ground, as discussed in the notes?

Accepted Answer

It is the result of induced emf due to the separation of charges, similar to a capacitor, where a region of higher potential (+q) and lower potential (-q) attract each other.

Question 2

A conducting rod of length $$L$$ moves with velocity $$v$$ perpendicular to a constant magnetic field $$B. $$What is the expression for the motional emf ($$\xi) $$induced across the ends of the rod?

Accepted Answer

$$\xi = vBL$$

Question 3

Which of the following scenarios will NOT result in an induced emf according to the notes?

Accepted Answer

A coil is stationary in a constant magnetic field.

Question 4

According to Faraday’s Law, what is the correct formula for the induced emf ($$\xi) in a $$coil with $$N$$ turns when the magnetic flux ($$\Phi_B) $$changes over time?

Accepted Answer

$$\xi = -N \dfrac{d\Phi_B}{dt}$$

Question 5

A rectangular loop of wire with area $$A is $$placed in a uniform magnetic field $$B at an $$angle $$	heta to $$the normal of the loop. What is the expression for the magnetic flux ($$\Phi_B) $$through the loop?

Accepted Answer

$$\Phi_B = (B \cos 	heta) A$$

Question 6

Which of the following best explains Lenz’s Law?

Accepted Answer

The induced current always flows in a direction that opposes the change in magnetic flux that produced it.

Question 7

A coil with 50 turns and area $$0.02\ \mathrm{m}^2 is $$placed in a uniform magnetic field of $$0.3\ \mathrm{T}. If $$the field is perpendicular to the coil and drops to zero in $$0.1\ \mathrm{s}$$, what is the magnitude of the average induced emf?

Accepted Answer

$$3\ \mathrm{V}$$

Question 8

Which of the following real-life examples is best explained by the concept of a Faraday Cage?

Accepted Answer

A person inside a car is protected from lightning because the metal body redistributes the charge around the outside.

Question 9

If the area of a coil in a constant magnetic field is doubled in half the time, what happens to the induced emf?

Accepted Answer

It increases by a factor of 2.

Question 10

A rod of length $$0.5\ \mathrm{m}$$ moves at $$4\ \mathrm{m/s}$$ perpendicular to a $$0.2\ \mathrm{T}$$ magnetic field. What is the induced emf?

Accepted Answer

$$0.4\ \mathrm{V}$$

Question 11

Which of the following statements about magnetic flux ($$\Phi_B) is $$correct?

Accepted Answer

It is proportional to the number of magnetic field lines passing through a surface.

Question 12

A coil is connected to a light bulb. A bar magnet is quickly inserted into the coil and then held stationary. What happens to the brightness of the bulb?

Accepted Answer

It lights up only while the magnet is moving.

Question 13

Which equation correctly relates the induced emf ($$\xi$$), current ($$I$$), and resistance ($$R) in a $$circuit?

Accepted Answer

$$\xi = IR$$

Question 14

If the magnetic field through a coil is increasing, what is the direction of the induced current according to Lenz’s Law?

Accepted Answer

It will flow in a direction that creates a magnetic field opposing the increase.

Question 15

A transformer in your home uses Faraday’s Law for safety. What happens if the magnetic flux in the transformer changes rapidly?

Accepted Answer

A circuit breaker is triggered to stop the current, preventing electric shock.

Question 16

Which of the following is the correct unit for magnetic flux ($$\Phi_B$$)?

Accepted Answer

Weber (Wb)

Question 17

A stationary coil is placed near a wire carrying a time-varying current. What will happen in the coil?

Accepted Answer

An emf will be induced due to the changing magnetic field.

Question 18

Which of the following best describes the relationship between the number of turns ($$N) in a $$coil and the induced emf ($$\xi$$)?

Accepted Answer

The induced emf is directly proportional to the number of turns.

Question 19

If both the magnetic field and the coil are moving together at the same velocity, what is the induced emf?

Accepted Answer

Zero, because there is no relative motion between the field and the coil.

Question 20

Which of the following equations correctly expresses the power ($$P) $$dissipated in a resistor due to an induced current ($$I) $$and resistance ($$R$$)?

Accepted Answer

$$P = I^2$ R$$

Chapter 29 - Electromagnetic Induction and Faraday’s Law – Study Notes

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