If a power of $100\, W$ is being supplied across a potential difference of $200\, V$,the current flowing is ............ $A$.

$A$ Watt-hour meter measures:

If the power in the external resistance $R$ is maximum,then which of the following statements are correct?
$(i) R = r$
$(ii)$ Power in $R$ is $\frac{E^2}{4R}$
$(iii)$ Input power is $\frac{E^2}{2R}$
$(iv)$ Efficiency is $50\%$

$A$ $10\, \Omega$ electric heater operates on a $110\, V$ line. Calculate the rate at which it develops heat in $watts$.

Heat produced in a wire of resistance $R$ due to current flowing at constant potential difference is proportional to

According to Joule's law,if the potential difference across a conductor having a material of specific resistance remains constant,then the heat produced in the conductor is directly proportional to