Question

All bulbs consume same power. The resistance of bulb $1$ is $36\Omega$.


$\left(i\right)$ What is the resistance of bulb $3?$

• A. $4\Omega$
• B. $9\Omega$
• C. $12\Omega$
• D. $18\Omega$

Answer 1

The correct option is B $9\Omega$

From the figure, Bulbs $2$ and $3$ are in series and both consume same power.

Therefore , $R_2=R_3$

Further, $V_1=V_{23}$ and $V_2=V_3$

Thus, $V_2=V_3=\frac{V_1}{2}$

Since, Power $\left(P\right)=\frac{V^2}{R}$

We can say, resistance should becomes ${\left(\frac{1}{4}\right)}^{th}$.

Hence, $R_2=R_3=\frac{R_1}{4}=9\Omega$