20.2 Electromagnetic Induction

A circular coil with an area of 0.1 m² and 500 turns is placed with its plane perpendicular to a horizontal magnetic field of uniform flux density 80 mT as shown in Fig. 1.1.

Fig. 1.1

Calculate the magnetic flux passing through the coil. Give a unit with your answer.

The coil experiences a change in magnetic flux linkage when it is rotated through 90° about a vertical axis (indicated in Fig. 1.1).

The coil rotates through 90° in a time of 300 ms.

Calculate the average magnitude of the induced e.m.f. in the coil during the rotation.

Table 1.1 shows the standard international (SI) units of the main quantities involved in electromagnetic induction.

Table 1.1

Complete Table 1.1 by filling in the missing quantities, symbols and SI units.

A coil is connected to a voltmeter, which is centred at zero as shown in Fig. 1.1a.

Fig. 1.1a

When the magnet is lowered into the coil, the needle on the voltmeter deflects to the right as shown in Fig. 1.1b.

Fig. 1.1b

On Fig. 1.1c, sketch the expected observations of the voltmeter needle when

Fig. 1.1c

[3]

The magnet is moved towards and away from the coil at a steady rate.

Fig. 1.2 shows the variation of time with the reading of potential difference on the voltmeter.

Fig. 1.2

Use Fig. 1.2 and Faraday’s law to explain why

As the magnet is moved away from the coil, the voltmeter shows a value of 1.5 mV for 2.0 s.

Calculate the change in magnetic flux linkage as the magnet is moved away from the coil.