The heat produced per unit time,on passing electric current through a conductor at a given temperature,is directly proportional to . . . . . . .

It takes $12$ minutes to boil $1$ litre of water in an electric kettle. Due to some defect, it becomes necessary to remove $20\%$ of the turns of the heating coil of the kettle. After repair, how much time will it take to boil $1$ litre of water?

An electric fan and a heater are marked as $100 \ W, 220 \ V$ and $1000 \ W, 220 \ V$ respectively. The resistance of the heater is

Power dissipated across the $8 \,\Omega$ resistor in the circuit shown here is $2 \,\text{W}.$ The power dissipated in watt units across the $3 \,\Omega$ resistor is

The battery of a mobile phone is rated as $4.2 \ V, 5800 \ mAh$. How much energy is stored in it when fully charged (in $kJ$)?

$A$ 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 $.............$.