$A$ battery of $e.m.f.$ $E$ is connected in series with a resistor $R$ and a voltmeter $V$. An ammeter $A$ is connected in parallel with the battery. Then:

If a battery of voltage $V$ is connected across terminals $I$ of the black box shown in the figure,an ideal voltmeter connected to terminals $II$ gives a reading of $V/2$. While if the battery is connected to terminals $II$,a voltmeter across terminals $I$ reads $V$. The black box may contain:

For a thermocouple,the temperature of inversion is that temperature at which the thermo $e.m.f.$ is:

$A$ cell of emf $\varepsilon$ and internal resistance $r$ is connected across a variable load resistance $R$. The graph drawn between its terminal voltage $V$ and resistance $R$ is

Two cells $A$ and $B$ of emf $2 \text{ V}$ and $1.5 \text{ V}$ respectively, are connected as shown in the figure through an external resistance $10 \text{ } \Omega$. The internal resistance of each cell is $5 \text{ } \Omega$. The potential difference $V_{A}$ and $V_{B}$ across the terminals of the cells $A$ and $B$ respectively are:

Consider a block of conducting material of resistivity $\rho$ shown in the figure. Current $I$ enters at $A$ and leaves from $D$. We apply the superposition principle to find the voltage $\Delta V$ developed between $B$ and $C$. The calculation is done in the following steps: $(i)$ Take current $I$ entering from $A$ and assume it to spread over a hemispherical surface in the block. $(ii)$ Calculate the field $E(r)$ at distance $r$ from $A$ by using Ohm's law $E=\rho j$,where $j$ is the current per unit area at $r$. $(iii)$ From the $r$ dependence of $E(r)$,obtain the potential $V(r)$ at $r$. $(iv)$ Repeat $(i), (ii)$ and $(iii)$ for current $I$ leaving $D$ and superpose results for $A$ and $D$. $\Delta V$ measured between $B$ and $C$ is