Question

In the circuit diagram, all the bulbs are identical. Which bulb will be the brightest?

• A. A
• B. B
• C. C
• D. D

Answer 1

The correct option is C C

Always the brightest bulb will be the one with the highest power dissipation.
$P=i^{2}R.$
So since R is the same for all bulbs, we just have to find which bulb has highest current.

If current through D is i, Then through A and B is $\frac{i}{2}$ (Since that branch has double the resistance, and hence half the current), and through C is 3 $\frac{i}{2}$.
\therefore Obviously C will glow the brighest.