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?

$A$ light bulb operates at a voltage $V_0$ and consumes power $P_0$. If the voltage is changed to $V$,what is the new power $P$ consumed by the bulb?

You are given three bulbs of $25\, W$,$40\, W$,and $60\, W$. Which of them has the lowest resistance?

The resistance of an electrical toaster has a temperature dependence given by $R(T) = R_0[1 + \alpha(T - T_0)]$ in its range of operation. At $T_0 = 300\,K, R = 100\,\Omega$ and at $T = 500\,K, R = 120\,\Omega$. The toaster is connected to a voltage source of $200\,V$ and its temperature is raised at a constant rate from $300\,K$ to $500\,K$ in $30\,s$. The total work done in raising the temperature is:

$A$ 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........$J.$

In an electric heater, $4\, A$ current passes for $1\, \text{minute}$ at a potential difference of $250\, V$. The power of the heater and the energy consumed will be, respectively: