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Question

A cell of emf 'E' and internal resistance 'r' is connected across a variable load resistor R. Draw the plots of the terminal voltage V versus (i) R and (ii) the current I.
It is found that When R=4Ω, the current is 1 A and when R is increased to 9Ω, the current reduces to 0.5 A. Find the values of the emf E and internal resistance r.

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Solution

current in the circuit is given by

I=εR+r

Terminal voltage V=IR=VAVBV=εIR+r=εIrI=ε4+rr+4=ε(1)0.5=ε9+r0.5r+4.5=ε(2)

On solving (1) and (2), we have ε=5V EMF

R=54=1Ω Internal resistance


890538_472107_ans_cbad0bca4bd94bb1b6e337437e702839.JPG

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