Question

Two bulbs A & B rated [200V, 50W] and [200V; 100W] are connected in series. Which will glow brighter?

• A. Bulb B
• B. Bulb A
• C. Same brightness
• D. 'A’ glows; ‘B’ does not

Answer 1

The correct option is B

Bulb A

Since in series, the flow of current is constant. We need to compare power with ‘R’.

P = V $\times$ I

$\Rightarrow$ P = $\frac{V^2}{R}$

$R_A$ = $\frac{{200}^2}{50}$ = 800 $\Omega$

$R_B$ = $\frac{{200}^2}{100}$ = 400 $\Omega$

Since, current is constant in P = $i^2$ R. More the resistance more will be the power and thus, the bulb glows more brightly.

Hence, Bulb A glows more.