Question:
A torch bulb rated as 4.5 W, 1.5 V is connected in the circuit as shown in the figure. If the bulb glows with maximum intensity, then the emf (E) is nearly
A torch bulb rated as 4.5 W, 1.5 V is connected in the circuit as shown in the figure. If the bulb glows with maximum intensity, then the emf (E) is nearly
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To find the emf, use the relation between power, resistance, and current in circuits with bulbs or resistors.
Updated On: Mar 16, 2026
- 4.5 V
- 1.5 V
- 2.67 V
- 13.5 V
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The Correct Option is C
Solution and Explanation
The power dissipated by the bulb is given by:
\[
P = I^2 R
\]
where \( P = 4.5 \, \text{W} \) and \( V = 1.5 \, \text{V} \). The resistance \( R \) of the bulb can be found using Ohm's law:
\[
R = \frac{V^2}{P} = \frac{(1.5)^2}{4.5} = 0.5 \, \Omega
\]
Now, the total resistance in the circuit is \( R + 1 \, \Omega = 1.5 \, \Omega \). Using the formula for the emf:
\[
E = I (R + 1)
\]
Substituting the values, we find that the emf is 2.67 V.
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