Question

An electrical appliance having a resistance of $200\Omega$ is operated at 200 V. Calculate the energy consumed by the appliance in 5 minutes (i) in joule, (ii) in kWh.

Answer 1

(i) $R=200\Omega V=200Vt=5mins=300s$

Now, energy consumed, $H=\frac{V^2}{R}t=\frac{{200}^2}{200}\times 300=60000J$

(ii) $P=\frac{V^2}{R}=\frac{{200}^2}{200}=200W=0.2kW$

$t=5mins=\frac{5}{60}h=\frac{1}{12}h$

Energy consumed, $H=Pt=0.2\times \frac{1}{12}=0.0167kWh$