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A torch bulb rated 4.5 W, 1.5 V is conne...

A torch bulb rated `4.5 W, 1.5 V` is connected as shown in Fig. 7.35. The emf of the cell needed to make the bulb glow at full intensity is

A

4.5V

B

1.5V

C

2.67V

D

13.5V

Text Solution

Verified by Experts

The correct Answer is:
D
When bulb glows with full intensity, potential difference across it is 1.5 V. So current through the bulb and resistance of `1Omega` are 3A and 1.5 A respectively. So main current from the cell j = 3 + 1.5 = 4.5 A. By using E = V + iR E= `1.5 +4.5 xx 2.67` = 13.5 V.
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