Question

Ten identical batteries each of emf $2\,V$ are connected in series to a $8\, \Omega$ resistor. If the current in the circuit is $2\, A$, then the internal resistance of each battery is

• A. $0.2 \,\Omega$
• B. $0.3 \,\Omega$
• C. $0.4 \, \Omega$
• D. $0.5 \,\Omega$
• E. $1 \,\Omega$

Answer 1

Answer: (A)

For this circuit,
$I=\frac{E_{\text {eff }}}{R_{\text {elr }}}$
So, $2 =\frac{20}{8+10 r} $
$16+20 r =20$
$20 r =20-16$
$r =\frac{4}{20} $
$r =\frac{1}{5}=0.2 \,\Omega$