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A cell gives a current of 0.15A through a resistance of 8...

A cell gives a current of 0.15A through a resistance of 8Ω and 0.3A. When the resistance is changed to 3Ω the internal resistance of the cell is

A.

0.05Ω

B.

1.00Ω

C.

1.50Ω

D.

2.00Ω

E.

2.50Ω

Correct answer is D

The E.M.F of a circuit is given by 

E=I(R+r)

Hence, E = 0.15(8+r)  = 0.3(3+r)

1.2 + 0.15r = 0.9 + 0.3r

1.2 - 0.9 = 0.3r - 0.15r

0.3 = 0.15r

r = 0.30.15

r = 2Ω