Question

A person connects four $\frac{1}{4}\Omega$ cells in series but one cell has its terminal reversed. The external resistance is $1\Omega$. If each cell has an emf of 1.5 V, the current flowing is

• A. $\frac{4}{3}A$
• B. $\frac{3}{4}A$
• C. 1.5 A
• D. Zero

Answer 1

The correct option is C 1.5 A

Equivalent e.m.f of the circuit $E_{eq}=3E-E=2E=2\times 1.5=3$ V

Equivalent resistance of the circuit $r_{eq}=4r+R=4\times \frac{1}{4}+1=2\Omega$

$\therefore$ Current flowing $I=\frac{E_{eq}}{r_{eq}}=1.5$ A