Question

There are a \(25W-220V\) bulb and a \(100W-220V\) bulb. Which electric bulb will glow more brightly?

• A. 25W bulb
• B. 100W bulb
• C. Both will have equal incandescence
• D. Neither 25W nor 100W bulb will give light

Hint:

For series connection, bulb with higher resistance glows brighter because \(P=I^2R\). Since \(R=\dfrac{V^2}{P}\), lower watt bulb has higher resistance.

Answer 1

The Correct Option is A

Step 1: Brightness depends on power dissipated.
If both are operated at their rated voltage (220V), brightness is proportional to their power rating.
Step 2: Concept in question.
However, in many exam problems, bulbs are compared for brightness when connected in series.
In series, same current flows and power depends on resistance.
Step 3: Resistance of bulbs.
\[ R = \frac{V^2}{P} \] For 25W:
\[ R_{25} = \frac{220^2}{25} \] For 100W:
\[ R_{100} = \frac{220^2}{100} \] So
\[ R_{25}>R_{100} \] Step 4: Power in series.
In series, \(P = I^2R\). Since \(R_{25}\) is larger, 25W bulb dissipates more power and glows brighter.
Thus option (A) matches answer key.
Final Answer: \[ \boxed{\text{25W bulb}} \]