Current Electricity and Electrical InstrumentHard
Question
A cell of internal resistance 1Ω is connected across a resister. A voltmeter having variable resistance is used to measure potential difference across resistor. The plot of voltmeter reading V against G is shown. What is value of external resistor R? (G = Resistance of galvanometer)
Options
A.5 Ω
B.4 Ω
C.3 Ω
D.can′t be determined
Solution
When galvanometer resistance tends to infinity G → ∞
Potential difference across R is 20V ⇒ 20 = 24 - i × 1 ⇒ i = 4 A also 20 = 4 × A also 20 = 4 × R ⇒ R = 5Ω
Potential difference across R is 20V ⇒ 20 = 24 - i × 1 ⇒ i = 4 A also 20 = 4 × A also 20 = 4 × R ⇒ R = 5Ω
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