Question

Question 14
In an electrical circuit three incandescent bulbs A, B and C of rating 40 W, 60 W and 100 W respectively are connected in parallel to an electric source. Which of the following is likely to happen regarding their brightness?

(a) Brightness of all the bulbs will be the same
(b) Brightness of bulb A will be the maximum
(c) Brightness of bulb B will be more than that of A
(d) Brightness of bulb C will be less than that of B

Answer 1

(c) Brightness of bulb B will be more than that of A
We know $P=\frac{V^2}{R}$
$R_A=\frac{V^2}{40}$
$R_B=\frac{V^2}{60}$
$R_C=\frac{V^2}{100}$
$\Rightarrow R_A>R_B>R_C$
Since $R_A>R_B>R_C,I_C>I_B>I_A$
Hence the brightness of B will be more than that of A.