If a wire of resistance $20 \mathrm{\Omega }$ is covered with ice and a voltage of $210 \mathrm{V}$ is applied across the wire, then the rate of melting of ice is $(L_{\mathrm{ice}}=80 \mathrm{cal} {\mathrm{g}}^{-1})$

For the circuit shown, a shorting wire of negligible resistance is added to the circuit between points $A$ and $B$. When this shorting wire is added, bulb $3$ goes out. Which bulbs (all identical) in the circuit are brightened?

A charge passing through a resistor varies with time as shown in the figure. The amount of heat generated in time $t$ is best represented (as a function of time) by