The measurement of voltmeter in the following circuit is

The measurement of voltmeter in the following circuit is
  1. $2.25 \mathrm{~V}$
  2. $4.25 \mathrm{~V}$
  3. $2.75 \mathrm{~V}$
  4. $6.25 \mathrm{~V}$

Solution

Resistance of voltmeter and $60 \Omega$ are in parallel. $\therefore \quad$ Equivalent resistance $=\frac{60 \times 40}{60+40}=\frac{60 \times 40}{100}=24 \Omega$ For the whole circuit, current $I=\frac{6 \mathrm{~V}}{(40+24) \Omega}=\frac{6}{64}=\frac{3}{32} \mathrm{~A}$ The voltmeter reads potential difference across $60 \Omega$. $\begin{aligned} & \therefore \quad \text { Voltmeter reading }=I \times R_{e q} \\ & \qquad=\frac{3}{32} \times 24=\frac{9}{4} \mathrm{~V}=2.25 \mathrm{~V}\end{aligned}$

Asked in: NEET 2014

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