Question

A student is asked to connected four cells of e.m.f of $1V$ and internal resistance $0.5ohm$ in series with an external resistance of $1ohm$. But one cell is wrongly connected by him with its terminal reversed. the current in the circuit is

• A. $\frac{1}{3}A$
• B. $\frac{2}{3}A$
• C. $\frac{3}{4}A$
• D. $\frac{4}{3}A$

Answer 1

The correct option is B $\frac{2}{3}A$

Using Kirchhoff's law

$-iR-ir-V-ir+V-ir+V-ir+V=0$

$\Rightarrow i=\frac{2}{1+4\times 0.5}$

$=\frac{2}{3}A$