First slide

Ohm's law

Question

The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of $10 Ω$ is

Easy

A

$0.8 Ω$
B

$1.0 Ω$
C

$0.2 Ω$
D

$0.5 Ω$

Solution

$I = \frac{ε}{R + r} o r I R + I r = ε$
$H e r e, R = 10 Ω, r = ?, ε = 2.1 V, I = 0.2 A ∴ 0.2 \times 10 + 0.2 \times r = 2.1 2 + 0.2 r = 2.1 0.2 r = 0.1 o r r = \frac{1}{2} = 0.5 Ω$

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