Question

In figure the emf of the cell is $2V$ and internal resistance is negligible. The resistance of the voltmeter is $80$ ohm. The reading of the voltmeter will be

• A. $2$ volt
• B. $1.33$ volt
• C. $1.60$ volt
• D. $0.80$ volt

Answer 1

The correct option is B $1.33$ volt

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

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.$=\frac{1}{3}A$

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

P.D across $80\Omega$ resistance=$\frac{1}{60}\times 80=1.331V$