In the electrical circuit shown in figure, the potential across $4\mathrm{\Omega }$resistor is:

For a metallic conductor, current versus voltage graph is drawn at two different temperatures ${\mathrm{T}}_1$ and ${\mathrm{T}}_2$. From the graph it follows:

What will be the value of $\mathrm{R}$ in the following circuit? 

Seven identical lamps of resistance $220 \mathrm{\Omega }$ each are connected to a $220 \mathrm{V}$ line as shown in figure. Then the reading in the ammeter will be:

Three identical bulbs are connected to a battery as shown in figure when the circuit is closed by means of the switch $\mathrm{S}$, it is found that:

Which switch in the circuit (shown in figure) when closed will produce short-circuiting?