An ammeter and a voltmeter are joined in series to a cell. Their readings are $A$ and $V$, respectively. If a resistance is now joined in parallel with the voltmeter, 

Between which points should the terminals of unknown resistance be connected in a post office box arrangement to get its value?

Let $V$ and $I$ be the readings of the voltmeter and the ammeter respectively as shown in the figure. Let $R_{\mathrm{V}}$ and $R_{\mathrm{A}}$ be their corresponding resistance Therefore,

A $10 \mathrm{ohm}$ resistor is connected to a supply voltage alternating between $+4\mathrm{V}$ and $–2\mathrm{V}$ as shown in the following graph. The average power dissipated in the resistor per cycle is 

In the circuit shown below, $E_1=3 \mathrm{V},$ $E_2=2 \mathrm{V},$ $E_3=1 \mathrm{V},$and$R=r_1=r_2=r_3=1 \mathrm{\Omega }$. $\left(\mathrm{i}\right)$Find potential difference between the points $\mathrm{A}$and $\mathrm{B}$ with $\mathrm{A} \& \mathrm{B}$ disconnected.
$\left(\mathrm{ii}\right)$ If ${\mathrm{r}}_{2 }$is short-circuited and the point $\mathrm{A}$ is connected to point $\mathrm{B}$ by a zero resistance wire, find the current through $R$.

The resistance of each resistor in the circuit diagram shown in figure is the same and equal to $R=1 \mathrm{\Omega }.$ The voltage across the terminals is $U = 7 \mathrm{V}.$ Determine the current $i$ (Ampere) the leads if their resistance can be neglected.