To determine the resistance $(R)$ of a wire,a circuit is designed as shown below. The $V-I$ characteristic curve for this circuit is plotted for the voltmeter and the ammeter readings as shown in the figure. The value of $R$ is . . . . . . . $\Omega$.

$A$ current of $1.5\, A$ flows through a copper voltameter. The thickness of copper deposited on the electrode surface of area $50\, cm^2$ in $20\, min$ will be (Density of copper $= 9000\, kg/m^3$ and $E.C.E.$ of copper $= 0.00033\, g/C$).

$A$ battery has an $e.m.f.$ of $4 \ V$ and an internal resistance of $r$. When the battery is connected to an external resistance of $2 \ \Omega$,a current of $1 \ A$ flows through the circuit. If the terminals of the battery are short-circuited (connected directly),what will be the current in $A$ flowing through it?

The storage battery of a car has an $emf$ of $12\; V$. If the internal resistance of the battery is $0.4\; \Omega,$ what is the maximum current (in $A$) that can be drawn from the battery?

$A$ potential divider is used to give outputs of $4\,V$ and $8\,V$ from a $12\,V$ source. Which combination of resistances,$(R_1 : R_2 : R_3)$ gives the correct voltages?

When a resistance of $9 \,\Omega$ is connected across the terminals of a battery,its potential difference decreases from $40 \, V$ to $30 \, V$. The internal resistance of the battery is ............... $\Omega$.