A cell of constant e.m.f. is first connected to a resistance $$R1$$ and then connected to a resistance $$R2$$. If power delivered in both cases is same, then the internal resistance of the cell is

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Infinity Learn · Accepted Answer

Power dissipated $$=i2R$$ $$=$$  $$ER+r2R$$∴   $$ER1+r2R1$$ $$=$$  $$ER2+r2R2$$⇒  $$R1$$ $$R22$$ $$+$$  $$r2$$ $$+$$  $$2R2r$$ $$=$$ $$R2$$ $$R12+r2$$ $$+$$  $$2R1r$$⇒ $$R22R1$$ $$+$$ $$R1r2$$ $$+$$ $$2R1R2r=$$ $$R12R2$$ $$+$$ $$R2r2$$ $$+$$ $$2R1R2r$$⇒  $$R1$$ − $$R2r2$$ $$=$$  $$R1$$ − $$R2R1R2$$ ⇒  $$r=$$ $$R1R2$$

A cell of constant e.m.f. is first connected to a resistance R₁ and then connected to a resistance R₂. If power delivered in both cases is same, then the internal resistance of the cell is

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A cell of constant e.m.f. is first connected to a resistance R1 and then connected to a resistance R2. If power delivered in both cases is same, then the internal resistance of the cell is

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A cell of constant e.m.f. is first connected to a resistance R₁ and then connected to a resistance R₂. If power delivered in both cases is same, then the internal resistance of the cell is