Question

Two heating coils of resistances $10\Omega$ and $20\Omega$ are connected in parallel and connected to a battery of emf $12V$ and internal resistance $1\Omega$. The power consumed by them are in the ratio

• A. $1:4$
• B. $1:3$
• C. $2:1$
• D. $4:1$

Answer 1

The correct option is C $2:1$

Let the potential drop across $10\Omega$ or $20\Omega$ resistor be $V$.

Thus power consumed by $10\Omega$, $P_1=\frac{V^2}{R}=\frac{V^2}{10}W$

Similarly power consumed by $20\Omega$, $P_2=\frac{V^2}{20}W$

$\therefore$ Ratio of powers consumed $P_1:P_2=20:10=2:1$