Two resistance of 100Ω and 200Ω are connected in series with a battery of 4 V and negligible internal resistance. A voltmeter is used to measure voltage across 100Ω resistance, which gives reading as

Question

Two resistance of 100Ω and 200Ω are connected in series with a battery of 4 V and negligible internal resistance. A voltmeter is used to measure voltage across 100Ω resistance, which gives reading as 1 V . The resistance of voltmeter must be _______ Ω .

TestHub · Accepted Answer

Voltage across 200Ω = 4 − 1 = 3 V . Therefore, current through the battery, 200 3 ​ Now, equivalent resistance of R V ​ &100Ω , = R v ​ + 100 R v ​ 100 ​ For voltmeter, R v ​ + 100 R v ​ 100 ​ × 200 3 ​ = 1 ⇒ 3 R v ​ = 2 R v ​ + 200 ⇒ R v ​ = 200Ω

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