# Test Prep for AP® Courses

### 6.1Induced Emf and Magnetic Flux

1

To produce current with a coil and bar magnet you can

1. Move the coil but not the magnet.
2. Move the magnet but not the coil.
3. Move either the coil or the magnet.
4. It is not possible to produce current.
2

Calculate the magnetic flux for a coil of area 0.2 m2 placed at an angle of θ=60º (as shown in the figure above) to a magnetic field of strength 1.5 × 10-3 T. At what angle will the flux be at its maximum?

### 6.5Electric Generators

3

The emf induced in a coil that is rotating in a magnetic field will be at a maximum when

1. The magnetic flux is at a maximum.
2. The magnetic flux is at a minimum.
3. The change in magnetic flux is at a maximum.
4. The change in magnetic flux is at a minimum.
4

A coil with circular cross section and 20 turns is rotating at a rate of 400 rpm between the poles of a magnet. If the magnetic field strength is 0.6 T and peak voltage is 0.2 V, what is the radius of the coil? If the emf of the coil is zero at t = 0 s, when will it reach its peak emf?

### 6.7Transformers

5

Which of the following statements is true for a step-down transformer? Select two answers.

1. Primary voltage is higher than secondary voltage.
2. Primary voltage is lower than secondary voltage.
3. Primary current is higher than secondary current.
4. Primary current is lower than secondary current.
6

An ideal step-up transformer with turn ratio 1:30 is supplied with an input power of 120 W. If the output voltage is 210 V, calculate the output power and input current.

### 6.8Electrical Safety: Systems and Devices

7

Which of the following statements is true for an isolation transformer?

1. It has more primary turns than secondary turns.
2. It has fewer primary turns than secondary turns.
3. It has an equal number of primary and secondary turns.
4. It can have more, fewer, or an equal number of primary and secondary turns.
8

Explain the working of a ground fault interrupter (GFI).