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The internal resistance of a 2.1 V cell...

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

A

` 0.2 Omega`

B

`0.5 Omega`

C

`0.8 Omega`

D

`1.0 Omega`

Text Solution

Verified by Experts

The correct Answer is:
B
`I = 0.2 A`
` R = 10 Omega`
` E = 2.1 V`
` I = E/(R + r)`
`0.2 = (2.1)/(10 + r)`
` 0.2 (10 + r) = 2.1`
` 2+ 0.2 r = 2.1`
` 0.2r = 2.1 - 2`
` = 0.1`
` r= (0.1)/(0.2 ) = 1/2 = 0.5 Omega`
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