Question

A student connects four 1/4 ohm cells in series but one cell has its terminals reversed. If each cell has an emf of 1.5 V and the external resistance is 2 ohm , then the current flowing is

• A. 1A
• B. 1.5 A
• C. 2.5 A
• D. zero

Answer 1

The correct option is A 1A

Equivalent emf in series combination is given by,
$E_{eq}=E_1+E_2+....$
In the given question it will be,
$E_{eq}=1.5+1.5-1.5+1.5$
$R_{eq}=\frac{1}{4}+\frac{1}{4}+\frac{1}{4}+\frac{1}{4}+2$ ohm
Now, $I=\frac{E_{eq}}{R_{eq}}$
$I=1A$