A car has a fresh storage battery of e.m.f. 15 V and internal resistance $4×10^{-2}Ω$. If the starter motor draws a current of 85 A, what is the terminal voltage of the battery when the starter is on?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 11.6 V
The terminal voltage $V_{terminal}$ of a battery is related to the emf E and the current I drawn by load -
$V_{terminal}=E-Ir$
where,
$E$ (emf of the battery) = $15 V$
$r$ (internal resistance of battery) = $4×10^{-2}Ω$
I (current drawn) = 85 A
$V_{terminal}=15-(85×4×10^{-2})$
$=15-3.4$
$=11.6V$