Question

You are given an electric bulb of broken filament. You reconnect the filament. The bulb now glows brighter. Why?

Answer 1

1. When we reconnect the filament tactfully then the length of the filament is decrease.

$\because Resis\tan ce\left(R\right)=\frac{\rho l}{A}$ [Where $\rho$= Proportionality constant, l= length of the filament and A= Area of cross-section ]

From the above formula, we can say that resistance is directly proportional to the length of the filament

2. When we reconnect the filament then, the resistance of the filament decreases.

$\because Power\left(P\right)=\frac{V^2}{R}\to \left(i\right)$

[Where, V= potential, R= Resistance]

3. From equation (i) we can say that power is inversely proportional to the resistance. When the resistance decreases then it will increase the power.

As power increases, it will increase the brightness of the bulb.

Hence, the bulb glows brighter.