Question

A car has a fresh battery of e.m.f. $12V$ and internal resistance of $0.05\Omega$ . If the starter motor draws a current of $90A$, the terminal voltage when the starter is on will be

• A. $12V$
• B. $10.5V$
• C. $8.5V$
• D. $7.5V$

Answer 1

The correct option is D

$7.5V$

Step 1: Given

$E=12V$, $I=90A$,$R=0.05\Omega$

Now ,we have a relation

$V=E-Ir$

Where,

$V$ - terminal volatge

$\mathrm{I}$ - emf in the cell

$\mathrm{R}$ - internal resistance

Step 2: Calculate the voltage

$V=E-Ir$

$V=12-(90\times 0.05)$

$V=12-4.5$

$V=7.5V$

Therefore, Option (d) $V=7.5V$is the correct answer