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A Voltmeter Has a Resistance of 100 Ω. What Will Be Its Reading When It is Connected Across a Cell of E.M.F. 2v and Internal Resistance 20Ω? - Physics

Answer in Brief

A voltmeter has a resistance of 100 Ω. What will be its reading when it is connected across a cell of e.m.f. 2V and internal resistance 20Ω?

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Given: R = 100 Ω, r = 20 Ω, E = 2 V

To find: Reading of voltmeter (V)

Formula: V = E − Ir 

Calculation: Current through the circuit is given by

`I = E/(R +r) = 2/(100 + 20) = 2/120`

`I = 1/ 60 A`

From formula,

V = `2 - (1/60 xx 20)` = 2 − 0.3333

∴ V = 1.667 V

The reading on the voltmeter is 1.667 V

Concept: Galvanometer
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Balbharati Physics 12th Standard HSC Maharashtra State Board
Chapter 9 Current Electricity
Exercises | Q 20 | Page 229
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