The resistance of the rheostat shown in figure is $30 \mathrm{\Omega }.$ Neglecting the ammeter resistance, the ratio of minimum and maximum currents through the ammeter, as the rheostat is varied, will be 

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 $R$.