Question

For the given figure, which battery is doing positive work?

• A. $E_1$
• B. $E_2$
• C. Both $E_1$ and $E_2$
• D. None of these

Answer 1

The correct option is A $E_1$

From given figure, we can see that cells are in reverse polarity and also $E_1>E_2$. Therefore, $E_1$ dominants in the circuit and current will flow according to cell $E_1$.

$\therefore$ current start from positive terminal of $E_1$ and terminate at negative terminal of $E_1$ followed by path $\text{B}$ to $\text{A}$.


Therefore, direction of current is from $\text{B}$ to $\text{A}$.


We can see that, cell $E_1$ is discharging means it is doing positive work and cell $E_2$ is charging means it is doing negative work.

Hence, option $\left(a\right)$ is correct.
$$\begin{array}{c}\text{Why this question ?}\\ \text{Concept: If current in a cell goes from}\\ \text{positive terminal to negative terminal}\\ \text{then the cell does negative work.}\end{array}$$