Question

In the adjoining circuit, the e.m.f. of the cell is 2 volt and the internal resistance is negligible. The resistance of the voltmeter is 80 ohm. The reading of the voltmeter will be

• A. 0.80 volt
• B. 1.33 volt
• C. 1.60 volt
• D. 2.00 volt

Answer 1

The correct option is B 1.33 volt

Total resistance of the circuit $=\frac{80}{2}+20=60\Omega$

$\Rightarrow$ Main current $i=\frac{2}{60}=\frac{1}{30}A$

Combination of voltmeter and $80\Omega$ resistance is connected in series with $20\Omega$, so current through $20\Omega$ and this combination will be same $=\frac{1}{30}A$

Since the resistance of voltmeter is also $80\Omega 4$, so this current is equally distributed in $80\Omega$ resistance and voltmeter $(i.e\frac{1}{60}A$ through each)

P.D across $80\Omega$ resistance $=\frac{1}{60}\times 80=1.33V$