Question

An electric device gives out 5760 J of heat energy in 1 min, when current flows through it at a p.d. of 24 V. Find the resistance of the device.

Answer 1

H = 5760 J; V = 24 V; t = 1 min = 60 s

\[\text{Heat energy} = \frac{\mathrm{V}^{2} \times t}{\mathrm{R}}\]

\[\therefore \mathrm{R} = \frac{\mathrm{V}^{2} \times t}{\text{Heat energy}}\]

\[= \frac{24 \times 24 \times 60}{5760}\]

\[= \frac{34560}{5760}\]

\[= 6\ \Omega\]