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 emfof 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

Given : $r=\frac{1}{4}\Omega$ $E=1.5$ volts $R=1\Omega$

Equivalent potential difference of the circuit $E_{eq}=E+E+E-E=2E=2\times 1.5=3$ volts

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

$\therefore$ Current flowing through the circuit $I=\frac{E_{eq}}{R_{eq}}=\frac{3}{2}=1.5$ A