If a $2\, kW$ boiler is used everyday for $1$ hour, then the electrical energy consumed by the boiler in thirty days is .......... $units$.

How much heat (in $cal$) is produced when a $210 \, W$ bulb is kept on for $5 \, min$? (Given $J = 4.2 \, J/cal$)

$A$ resistor dissipates $192 \, J$ of energy in $1 \, s$ when a current of $4 \, A$ is passed through it. Now,when the current is doubled,the amount of thermal energy dissipated in $5 \, s$ is $..... \, J$.

An electrical cable having a resistance of $0.2 \Omega$ delivers $10 \text{ kW}$ at $200 \text{ V}$ $D$.$C$. to a factory. What is the efficiency of transmission (in $\%$)?

The resistance of a bulb filament changes with temperature. If a bulb rated at $220 \ V$ and $100 \ W$ is connected to a supply of $(220 \times 0.8) \ V$,the actual power consumed will be:

$A$ Watt-hour meter measures: