JEE MainPhysicsAlternating CurrentMCQ+4 / −1
An arc lamp requires a direct current of 10 A at 80 V to function. If it is connected to a 220 V (rms), 50 Hz AC supply, the series inductor needed for it to work is close to :
- A0.044 H
- B0.065 H
- C80 H
- D0.08 H
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Correct answer: B
- Lamp rating and required operating conditions
The arc lamp needs:
- Current:
- Voltage across lamp:
Since it works on direct current at and , we treat the lamp as an effective resistance:
- AC supply and series inductor
The lamp is connected to:
A pure inductor is connected in series so that the current remains .
For a series - circuit, the impedance is:
Also,
where .
So,
- Find inductance
Angular frequency:
Thus,
- Match with options
The closest option is:
So the correct option is B.
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