How many calories of heat will be produced approximately in a $210\, watt$ electric bulb in $5$ minutes .............. $cal $

An electric bulb of $500 \,watt$ at $100\, volt$ is used in a circuit having a $200\, {V}$ supply. Calculate the resistance ${R}$ to be connected in series with the bulb so that the power delivered by the bulb is $500\, {W}$. (in $\Omega$)

Two coils require $20$ minutes and $60$ minutes respectively to produce same amount of heat energy when connected separately to the same source. If they are connected in parallel arrangement to the same source; the time required to produce same amount of heat by the combination of coils, will be________ $min$

If $X, Y$ and $Z$ in figure are identical lamps, which of the following changes to the brightnesses of the lamps occur when switch $S$ is closed?

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 ................ $V$

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 cunsume now is