what is the current if a 1.2v battery light up a bulb which is rated 2.4V 500mA?

Question

what is the current if a 1.2v battery light up a bulb which is rated 2.4V 500mA? is it 250mA? and what is the current is a 2.4v battery light up a bulb which is rated 1.2V 250mA? is it 500mA?

Answer 1

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It will usually be a bit higher than half the current with half the voltage for incandescent bulbs because the resistance of the filament is much higher at operating temperature, about 5 times higher than at room temp if I remember right. So the current in the first case might be 250-350mA.

In the second case, at least 50% more to almost double the current of the rating of the bulb will flow, quickly burning out the bulb.

Answer 2

Light bulb filaments are nonlinear resistors, so simply halving the voltage does not necessarily halve the current. I have no idea what the answer is but I think Gary's on the right track.

Source(s): EE, 29 years experience