Resistance in the two gaps of a meter bridge are $10 \mathrm{\Omega }$ and $30 \mathrm{\Omega }$, respectively. If the resistances are inter changed, the balance point shifts by

Figure shows a potentiometer. Length of the potentiometer wire $AB$ is $100 \mathrm{cm}$ and its resistance is $100\Omega$. EMF of the battery $E$ is $2 \mathrm{V}$. A resistance $R$ of $50\Omega$ draws current from the potentiometer. What is the voltage across $R$ when the sliding contact $C$is at the mid-point of $AB ?$

In the circuit, the galvanometer $G$ shows zero deflection. If the batteries $A$ and $B$ have negligible internal resistance, then the value of $R$ is

A circuit is shown in the figure. The e.m.f. of the battery is

The value of current $i$ in the given figure is: