Q: A Boeing 747 with a wingspan of $$65\ \mathrm{m}$$ flies at $$260\ \mathrm{m/s}$$ perpendicular to Earth's magnetic field and a potential difference of $$0.95\ \mathrm{V} is $$measured between the wingtips. What is the strength of the magnetic field?

$$B = \frac{0.95}{65 \times 260}$$

Q: A circular loop of radius $$r is $$placed in a uniform magnetic field $$B at an $$angle $$\theta to $$the field. What is the magnetic flux through the loop?

$$\Phi_B = \pi r^2$ B \cos \theta$$

Question 1

Which of the following best describes the condition required for an induced current to be generated in a loop of wire?

Accepted Answer

The magnetic flux through the loop must be changing.

Question 2

The magnetic flux $$\Phi_B$$ through a loop of area $$A in a $$uniform magnetic field $$B at an $$angle $$	heta to $$the normal of the loop is given by which formula?

Accepted Answer

$$\Phi_B = AB \cos 	heta$$

Question 3

According to Lenz's law, the direction of an induced current in a closed loop is such that:

Accepted Answer

It opposes the change in magnetic flux through the loop.

Question 4

Faraday's law states that the magnitude of the induced emf $$\mathcal{E} in a $$loop is:

Accepted Answer

$$\mathcal{E} = -\frac{d\Phi_B}{dt}$$

Question 5

A metal bar of length $$l$$ moves at velocity $$v$$ perpendicular to a magnetic field $$B. $$What is the motional emf generated across the bar?

Accepted Answer

$$\mathcal{E} = vBl$$

Question 6

A Boeing 747 with a wingspan of $$65\ \mathrm{m}$$ flies at $$260\ \mathrm{m/s}$$ perpendicular to Earth's magnetic field and a potential difference of $$0.95\ \mathrm{V} is $$measured between the wingtips. What is the strength of the magnetic field?

Accepted Answer

$$B = \frac{0.95}{65 	imes 260}$$

Question 7

Which of the following is NOT a real-world application of electromagnetic induction?

Accepted Answer

Permanent magnets in compasses

Question 8

If the magnetic field through a stationary loop is increasing upward, what is the direction of the induced current as seen from above?

Accepted Answer

Counterclockwise

Question 9

A conducting loop is pulled out of a region with a uniform magnetic field pointing into the page. What is the direction of the induced current in the loop as it leaves the field?

Accepted Answer

Clockwise

Question 10

Which of the following statements about eddy currents is correct?

Accepted Answer

Eddy currents are induced in a conductor when it is moved through a changing magnetic field.

Question 11

A circular loop of radius $$r is $$placed in a uniform magnetic field $$B at an $$angle $$	heta to $$the field. What is the magnetic flux through the loop?

Accepted Answer

$$\Phi_B = \pi r^2$ B \cos 	heta$$

Question 12

Which law determines the direction of the induced current in a loop due to a changing magnetic flux?

Accepted Answer

Lenz's law

Question 13

A transformer is used to:

Accepted Answer

Change the voltage of an alternating current.

Question 14

If a bar magnet is pushed into a coil, what happens to the induced current as the magnet is held stationary inside the coil?

Accepted Answer

The induced current stops.

Question 15

Which of the following best describes the induced electric field created by a changing magnetic field?

Accepted Answer

It forms closed loops around the region of changing magnetic field.

Question 16

A generator converts:

Accepted Answer

Mechanical energy into electrical energy.

Question 17

If the area of a loop is doubled while the magnetic field and orientation remain constant, what happens to the magnetic flux through the loop?

Accepted Answer

It is doubled.

Question 18

Which of the following is the SI unit of magnetic flux?

Accepted Answer

Weber

Question 19

A metal loop is rotated in a uniform magnetic field. What is true about the magnetic flux through the loop?

Accepted Answer

The magnetic flux changes with time.

Question 20

Which of the following statements about electromagnetic induction is correct?

Accepted Answer

A changing electric field induces a magnetic field, and a changing magnetic field induces an electric field.

Electromagnetic Induction and Magnetic Flux: Chapter 30 Study Notes

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