A cell of emf 90 V is connected across series combination of two resistors each of 100 Ω resistance. A voltmeter of resistance 400 Ω is used to measure the potential difference across each resistor. T

Question

A cell of emf 90 V is connected across series combination of two resistors each of 100 Ω resistance. A voltmeter of resistance 400 Ω is used to measure the potential difference across each resistor. The reading of the voltmeter will be:

TestHub · Accepted Answer

As we know, voltmeter is connected in parallel to the element being measured.

The equivalent resistance of the above circuit is $R_{e q} = (\frac{400 \times 100}{400 + 100}) + 100 = 80 + 100 = 180 Ω$

Current through the circuit is $i = \frac{90}{180} = \frac{1}{2} A$

Reading of the voltmeter is $V_{R} = i (\frac{400 \times 100}{400 + 100}) = \frac{1}{2} \times 80 = 40 V$

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