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Grade 12Electric Current

A cell of EMF E and internal resistance r supplies currents for the same time t through external resistance R1 and R2 respectively. if the heat produced in both cases is the same then the internal resistance is

Ammar

8 Years agoGrade 12

1 Answer

Eshan

Approved Tutor Answer8 Years ago

Dear student,

Current flowing in the first circuit is $I_1=\dfrac{E}{R_1+r}$

Power of heat dissipation in the first circuit= $I_1^2R_1=\dfrac{E^2}{(R_1+r)^2}R_1$

Since heat dissipated in $t$ timeis same in both the circuits,

$\dfrac{E^2}{(R_1+r)^2}R_1=\dfrac{E^2}{(R_2+r)^2}R_2$
$\implies r=\sqrt{R_1R_2}$

The fig. Shows a network of resistance in which the point A is earthed

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