A battery of emf 4 V and internal resistance 1 \( \Omega \) is connected across the wire of resistance of 9.0 \( \Omega \). The number of electrons passing through the cross-section of the wire in 4 s is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \( 10^{19} \)
The battery drives a current through the total resistance, the external wire plus the internal resistance. The charge passed in time \( t \) is \( q = It \) and the number of electrons is \( q/e \).
\( \displaystyle I = \frac{E}{R + r} = \frac{4}{9 + 1} = 0.4\,\mathrm{A} \)
\( \displaystyle q = It = 0.4\times4 = 1.6\,\mathrm{C} \)
\( \displaystyle n = \frac{q}{e} = \frac{1.6}{1.6\times10^{-19}} = 10^{19} \)