In the given electric circuit, the potential difference across $PQ$ is approximately ...... volts.

$A$ $DC$ 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

Model a torch battery of length $l$ to be made up of a thin cylindrical bar of radius $a$ and a concentric thin cylindrical shell of radius $b$,filled in between with an electrolyte of resistivity $\rho$ (see figure). If the battery is connected to a resistance of value $R$,the maximum Joule heating in $R$ will take place for:

Two cells of $e.m.f.$ $E_1$ and $E_2$ and of negligible internal resistances are connected with two variable resistors as shown in the figure. When the galvanometer shows no deflection,the values of the resistances are $P$ and $Q$. What is the value of the ratio $E_2/E_1$?

$A$ battery of $e.m.f.$ $10\, V$ and internal resistance $0.5\, \Omega$ is connected across a variable resistance $R$. The value of $R$ for which the power delivered in it is maximum is given by ......... $\Omega$.

Five equal resistances each of resistance $R$ are connected as shown in the figure. $A$ battery of $V$ volts is connected between $A$ and $B$. The current flowing in $AFCEB$ will be