The wire used in the arrangement shown in the figure has a resistance of $r$ ohm per meter. The equivalent resistance between points $A$ and $B$ is

For the circuit of the figure the equivalent resistance between points $A$ and $B$ is

A $100 \mathrm{W}$ bulb $B_1$ and two $60 \mathrm{W}$ bulbs $B_2$ and $B_3$ are connected to a $250 \mathrm{V}$ source as shown in the figure. Now $W_1,W_2$ and $W_3$ are the output powers of the bulbs $B_1,B_2$ and $B_3$ respectively. Then

Two bars of equal resistivity $\rho$ and radii $r$ and $2r$ are kept in contact as shown. An electric current $I$ is passed through the bars. Which one of the following is correct?

From resistances of $100$ ohm each are connected in the form of a square. The effective resistance along the diagonal points $P R$ is 

The potential difference across $BC$ in the following figure will be