Question
A 20 V5 W lamp is to run on 200 V50 Hz a.c. mains. Find the capacitance of a capacitor required to run the lamp.

None of these



diffcult
Solution
The current ratting of the 20 V5 W lamp is
And the resistance of its filament is
If the lamp is to run on 200 V50 Hz a.c. mains, a capacitor (or choke) must be placed in series in order to increase its effective (impedance) so that the current through it does not exceed 0.25 A. Let C be the capacitance of the required capacitor. Then, the impedance of the lampcapacitor combination is
.
Now,
.
SIMILAR QUESTIONS
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