Question

An electric device consumes 5760 J of energy in 1.0 minute when the p.d. at its ends is 24 V. The electrical resistance of the device is:

Options

• 4.5 Ω

• 5 Ω

• 6 Ω

• 5.5 Ω

Answer 1

6 Ω

Explanation:

Convert 1.0 min to 60 s.

$$W = \frac{V^2}{R}t$$

$$R = \frac{V^2t}{W}$$

$$= \frac{24^2 \times 60}{5760}$$

$$= 6\ \Omega$$