Question

A 10V battery with internal resistance 1 $\Omega$ and a 15V battery with internal resistance $0.6\Omega$ are connected in parallel to a voltmeter. The reading in the voltmeter will be close to.

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

Answer 1

The correct option is B 13.1 V

Applying KVL in the circuit
$15-10-1\ast i-.6\ast i=0$ The current through voltmeter will be negligible as voltmeter have very high resistance.
$\Rightarrow i=\frac{5}{1.6}=\frac{25}{8}$
The voltmeter reading is given as potential difference across points A and B
$\Delta V=-i\ast .6+15=15-\frac{25}{8}\ast .6=15-1.875=13.12V$
reading across voltmeter will be 13.2 V, correct option is B.