Question

A $10\text{V}$ battery with internal resistance $\text{1}\Omega$ and a $15\text{V}$ battery with internal resistance $0.6\Omega$ are connected in parallel to a voltmeter (see figure). The reading in the voltmeter will be close to:

• A. $11.9V$
• B. $13.1V$
• C. $12.5V$
• D. $24.5V$

Answer 1

Answer: (B)

The equivalent emf of the battery parallel combination is given as
Equation $=\frac{\frac{E_1}{r_1}+\frac{E_2}{r_2}}{\frac{1}{r_1}+\frac{1}{r_2}}$
$=\frac{\frac{10}{1}+\frac{15}{0.6}}{\frac{1}{1}+\frac{1}{0.6}}=\frac{10+\frac{150}{6}}{1+\frac{10}{6}}$
$=\frac{105}{8}$
$=13.1V$
$\therefore$ The reading measured by voltmeter $=13.1V$