Question

The current in a circuit containing a battery connected to 2 $\Omega$resistance is 0.9 A. When a resistance of 7 $\Omega$connected to the same battery, the current observed in the circuit is 0.3 A. Then the internal resistance of the battery is

• A. 0.1$\Omega$
• B. 0.5$\Omega$
• C. 1$\Omega$
• D. Zero

Answer 1

The correct option is B 0.5$\Omega$

case 1 :-
$E=0.9(R+r)$
$E=0.9(2+r)$
case 2:-
$E=0.3(R+r)$
$E=0.3(7+r)$
$\Rightarrow 0.9(2+r)=0.3(7+r)$
$6+3r=7+r$
$2r=1$
$r=0.5\Omega$