Heating coils rated at $220\, V$ are available with resistances of $55\,\Omega$,$110\,\Omega$,$220\,\Omega$,and $440\,\Omega$. Which resistance value will produce the maximum power?

The heat produced by a $100\, W$ heater in $2\, minutes$ will be equal to:

$A$ potential $V_0$ is applied across a uniform wire of resistance $R$. The power dissipation is $P_1$. The wire is then cut into two equal halves and a potential of $V_0$ is applied across the length of each half. The total power dissipation across two wires is $P_2$. The ratio $P_2: P_1$ is $\sqrt{x}: 1$. The value of $x$ is $.............$.

An electric heater consists of a nichrome coil and runs under $220 \,V$,consuming $1 \,kW$ power. Part of its coil burned out and it was reconnected after cutting off the burnt portion. The power it will consume now is

$Kilowatt-hour$ $(kWh)$ is a unit of

Explain electrical energy and power.