The internal resistance of primary cell is 3 Ω. It generates a current of 0.3 A in an external resistance of 22 Ω. The rate at which chemical energy is consumed in providing the current is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \( 2.25\,\mathrm{J\,s^{-1}} \)
The chemical energy consumed per second is the power delivered by the emf of the cell, \( P = \varepsilon I \), where \( \varepsilon = I(R+r) \).
\( \varepsilon = 0.3\,\mathrm{A}\times(22+3)\,\Omega = 7.5\,\mathrm{V} \)
\( P = \varepsilon I = 7.5\,\mathrm{V}\times0.3\,\mathrm{A} = 2.25\,\mathrm{W} = 2.25\,\mathrm{J\,s^{-1}} \)