Forum Discussion

JamesJudasPries's avatar
JamesJudasPries
Explorer
Oct 19, 2016

Light bulb ohms. What the heck is going on here?

Hello This is really bugging me. I decided to measure a new incandescent light bulb I was installing at home with a multimeter, since it had no marking. I thought sure, I could figure out if thi...
Hiker_01's avatar
Hiker_01
Explorer
Oct 19, 2016
Voltage = Current x Resistance
Wattage = Voltage x Current

Combine the above
Wattage = Voltage (Current x Resistance) x Current
or
Wattage = Current x Current x Resistance

If you know Wattage and Resistance and want to find Current

Current = square root of (Wattage / Resistance)

Current = Square root of (40/32) = ~1.12 amps drawn

Current = Square root of (60/17) = ~1.85 amps drawn

So, it makes sense that a 60 watt bulb draws more amps. Looks like your measurements make sense.


Don

About RV Must Haves

Have a product you cannot live without? Share it with the community!8,800 PostsLatest Activity: Apr 28, 2025