$A$ railway compartment is lit up by thirteen lamps,each taking $2.1\,A$ at $15\,V$. The heat generated per second in each lamp will be ............ $cal$.

An electric heater heats a certain amount of water in $5 \, \text{min}$ when connected to a $220 \, \text{V}$ supply. How many minutes will it take to heat the same amount of water when connected to a $110 \, \text{V}$ supply?

$A$ resistance $R = 12 \, \Omega$ is connected across a source of $emf$ as shown in the figure. Its $emf$ changes with time as shown in the graph. What is the heat developed in the resistance in the first four seconds (in $, J$)?

If current in an electric bulb changes by $1\%$,then the power will change by ............ $\%$

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

$A$ resistor develops $300 \,J$ of thermal energy in $15 \,s$,when a current of $2 \,A$ is passed through it. If the current increases to $3 \,A$,the energy developed in $10 \,s$ is........$J.$