$A$ $DC$ source with internal resistance $R_0$ is connected to three identical resistors each of resistance $R$ as shown in the figure. If the thermal power generated in the circuit is highest,then

By error,a student places a moving-coil voltmeter $V$ (nearly ideal) in series with the resistance in a circuit in order to read the current,as shown. The voltmeter reading will be ............ $V$.

For the circuit shown in the figure,the power delivered by the battery is ................ $W$.

Two resistances $R_1$ and $R_2$ are made of different materials. The temperature coefficient of the material of $R_1$ is $\alpha$ and of the material of $R_2$ is $-\beta$. The resistance of the series combination of $R_1$ and $R_2$ will not change with temperature,if $R_1/R_2$ equals

In the given circuit,$(V_A - V_B) = \dots \dots \dots V$.

When the terminals of a cell are connected by a wire of resistance $4 \Omega$,the potential difference across the cell is $1.6 \text{ V}$. If a wire of the same resistance is connected in parallel with the first,the potential difference becomes $1.33 \text{ V}$. The emf and internal resistance of the cell are respectively