$A$ $5\,^{\circ}\text{C}$ rise in temperature is observed in a conductor by passing a current. When the current is doubled the rise in temperature will be approximately ........... $^{\circ}\text{C}$

$A$ heater of $220\, V$ heats a volume of water in $5\, \text{min}$ time. $A$ heater of $110\, V$ heats the same volume of water in ............... $\text{min}$.

$A$ lamp of $60 \, W, 230 \, V$ is used for $8 \, \text{hours}$. If the cost of $1 \, \text{unit}$ is $1.25 \, \text{Rs}$, what will be the total bill in $Rs$?

$A$ 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 $, J$)?

The battery of a mobile phone is rated as $4.2 \ V, 5800 \ mAh$. How much energy is stored in it when fully charged (in $kJ$)?

$A$ steady current $I$ flows through a wire of radius $r$,length $L$ and resistivity $\rho$. The current produces heat in the wire. The rate of heat loss in a wire is proportional to its surface area. The steady temperature of the wire is independent of