In the given circuit,the reading of the ideal voltmeter is $\frac{E}{2}$. Find the internal resistance $r$ of the cell in $\Omega$.

In the following circuit,the battery has an emf of $2 \ V$ and an internal resistance of $\frac{2}{3} \ \Omega$. The power consumption in the entire circuit is $..... \ W$.

Two resistances of $400 \Omega$ and $800 \Omega$ are connected in series with a $6 \text{ V}$ battery of negligible internal resistance. $A$ voltmeter of resistance $10000 \Omega$ is used to measure the potential difference across the $400 \Omega$ resistor. The error in the measurement of potential difference in volts is approximately:

$A$ resistor ${R_1}$ dissipates the power $P$ when connected to a certain generator. If the resistor ${R_2}$ is put in series with ${R_1}$,the power dissipated by ${R_1}$

An external resistance $R$ is connected to a battery of $e.m.f.$ $V$ and internal resistance $r$. The joule heat produced in resistor $R$ is maximum when $R$ is equal to

If the rheostat slider were to move from the extreme right to the far left,how will the reading of voltmeter $V_1$ change?