An electric heater rated $220 \,V$ and $550 \,W$ is connected to $AC$ mains. The current drawn by it is (in $\,A$)

$A$ current $i$ passes through a wire of length $l$, radius of cross-section $r$ and resistivity $\rho$. The rate of heat generation is

The same mass of copper is drawn into two wires $1 \, mm$ and $2 \, mm$ thick. Two wires are connected in series and current is passed through them. The ratio of heat produced in the wires is:

An electric kettle draws $4\, A$ current at $220\, V.$ How much time (in minutes) will it take to boil $1\, kg$ of water starting from a temperature of $20\, ^oC$? (Assume the boiling point of water is $100\, ^oC$ and specific heat capacity of water is $4.2\, J/g\, ^oC$)

For driving a current of $2\, A$ for $6$ minutes in a circuit, $1000\, J$ of work is to be done. The $e.m.f.$ of the source in the circuit is ................ $V$.

Which of the following is not a unit of power?