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A cell of e.m.f. 1.5v is connected in series with a resis...

A cell of e.m.f. 1.5v is connected in series with a resistor of 3Ω. A high resistance voltmeter connected across the cell registers only 0.9v. Calculate the internal resistance of the cell

A.

5.0Ω

B.

4.5Ω

C.

2.4Ω

D.

2.0Ω

E.

1.8Ω

Correct answer is D

E.M.F (E) = 1.5v, Internal Resistance (r) = ?, Potential Difference (V) =  0.9v, Load resistance (R) = 3Ω,

Current (I) = V / R = 0.9 / 3 = 0.3A

USING : E = I ( R + r )

r = (E / I) - R = (1.5 / 0.3) - 3

r = 5 - 3 

r = 2Ω,