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 $E_2/E_1$?

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:

The current in a simple series circuit is $5.0 \, A$. When an additional resistance of $2.0 \, \Omega$ is inserted, the current drops to $4.0 \, A$. The original resistance of the circuit in $\Omega$ was:

The diagram shows a circuit. Choose the incorrect statement.

Find the current in the circuit. (in $ A$)

In the figure shown,the capacity of the capacitor $C$ is $2\,\mu F$. The current in the $2\,\Omega$ resistor is ............... $A$.