Q: The third image shows an airplane flying. If the airplane's wingspan is $$l = 70\ \mathrm{m}$$ and it flies at $$v = 280\ \mathrm{m/s}$$ perpendicular to Earth's vertical magnetic field $$B = 5 \times 10$$^{-5}$$\ \mathrm{T}$$, what is the induced emf between the wingtips?

$$e = Blv = (5 \times 10$$^{-5}$$)(70)(280) = 0.98\ \mathrm{V}$$

Q: A transformer is shown in the fourth image. If the primary coil has $$N_P = 100$$ turns and the secondary coil has $$N_S = 400$$ turns, and the input voltage is $$V_P = 120\ \mathrm{V}$$, what is the output voltage $$V_S$$?

$$V_S = V_P \frac{N_S}{N_P} = 120 \times \frac{400}{100} = 480\ \mathrm{V}$$

Question 1

Which physical principle is being demonstrated in the first image, where a bar magnet is moved into and out of a coil connected to a galvanometer?

Accepted Answer

Faraday's Law of Electromagnetic Induction

Question 2

In the second image, an induction stove is shown heating a metal pan. Why does the induction stove heat the pan but not the glass cooktop?

Accepted Answer

The changing magnetic field induces currents only in conductive materials like the pan, not in the insulating glass.

Question 3

The third image shows an airplane flying. If the airplane's wingspan is $$l = 70\ \mathrm{m}$$ and it flies at $$v = 280\ \mathrm{m/s}$$ perpendicular to Earth's vertical magnetic field $$B = 5 	imes 10$$^{-5}$$\ \mathrm{T}$$, what is the induced emf between the wingtips?

Accepted Answer

$$e = Blv = (5 	imes 10$$^{-5}$$)(70)(280) = 0.98\ \mathrm{V}$$

Question 4

The fourth image shows a worker repairing a device on a utility pole. What is the main function of the large cylindrical device next to the worker?

Accepted Answer

It is a transformer that steps down the high transmission voltage to a lower voltage suitable for home use.

Question 5

The fifth image shows a person walking through a security device at an airport. What physical principle allows this device to detect metal objects?

Accepted Answer

Electromagnetic induction creates eddy currents in metal objects, which are detected by the device.

Question 6

The sixth image shows a hard disk drive. How does electromagnetic induction play a role in reading and writing data on this device?

Accepted Answer

A changing magnetic field in the read/write head induces an emf in the disk, allowing data to be read or written.

Question 7

The seventh image shows a special type of electrical outlet with 'test' and 'reset' buttons. What is the main safety function of this device?

Accepted Answer

It is a Ground Fault Circuit Interrupter (GFCI) that disconnects power if it detects a difference in current between the hot and neutral wires.

Question 8

The eighth image shows a yellow device being plugged into an outlet. What is the purpose of this device?

Accepted Answer

It is a portable GFCI that provides ground fault protection for devices plugged into it.

Question 9

Which of the following best describes the role of eddy currents in the operation of a metal detector, as seen in the fifth image?

Accepted Answer

Eddy currents induced in metal objects create their own magnetic fields, which are detected by the device.

Question 10

A transformer is shown in the fourth image. If the primary coil has $$N_P = 100$$ turns and the secondary coil has $$N_S = 400$$ turns, and the input voltage is $$V_P = 120\ \mathrm{V}$$, what is the output voltage $$V_S$$?

Accepted Answer

$$V_S = V_P \frac{N_S}{N_P} = 120 	imes \frac{400}{100} = 480\ \mathrm{V}$$

Question 11

Which of the following is a necessary condition for electromagnetic induction to occur in the experiment shown in the first image?

Accepted Answer

There must be a change in magnetic flux through the coil.

Question 12

In the induction stove shown in the second image, what would happen if a glass pan were used instead of a metal pan?

Accepted Answer

Little or no current would be induced, so the pan would not heat up.

Question 13

Which equation correctly expresses Faraday's Law of Induction for a coil with $$N$$ turns?

Accepted Answer

$$e = -N \frac{d\Phi_B}{dt}$$

Question 14

A hard drive (sixth image) stores information using which of the following physical effects?

Accepted Answer

Magnetization of small regions on the disk surface, read and written by electromagnetic induction.

Question 15

A GFCI (seventh and eighth images) protects against which type of electrical hazard?

Accepted Answer

Current leakage to ground that could cause electric shock.

Electromagnetic Induction and Faraday’s Law: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards