Light Bulb Lamp

May 24
2009

G10T5L 4P 16W 16 watt UV UVC Germicidal Light Bulb Lamp
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US $20.00

G7T5 7W 7 watt Bi Pin UV UVC Germicidal Light Bulb Lamp
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US $8.00

G10T55L 16W 16 watt UV UVC Germicidal Light Bulb Lamp
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US $16.99

resistance of a lamp (light bulb to the uninitiated)?

I asked a question earlier about lamp resistance. There were some respectable answers. But.... Work it out again - lamp (bulb) 240v 100w. Resistance in ohms = ? Then get your multimeter out and set it to whatever to read the resistance - and DOES IT AGREE WITH YOUR ALGEBRAIC ANSWER?

If you have a 240V 100 watts lamp, you can assume that the resistance of the lamp when it is under power will follow the ohms law.

BUT, one thing you must remember is, when a lamp is under load, it is glowing HOT. When metal is HOT, the molculoes of the meals are in much more active state. When this happens, the resistance will increase. Conversely, when the lamp is NOT on ON state, the filaments are cold. Moleculoes in the filaments are not as active. Thus, the resistance is lower. There is almost 10 to 1 difference in resistance from hot to cold.

Taking out a multimeter and measuring the resistance of the lamp will not help you determine the resistance of the lamp when it is actually under load (with voltage applied) Really, the only thing you can do is to measure the voltage, measure the current, then arrive at the resistance mathmatically.

Does this help you?

By the way, regular lamp under 60Hz is almost all pure resistance with little reactance. So, no, AC/DC difference is not what you are looking at....