using lamp as resistor

[thebadtall]

Hello, I measured a typical lamp and is 100Ohm / 40W
Can I use it as replacement of a high wattage resistor of same value ?
Thank you

 

[alexan_e]

The resistance when an incandescent bulb is cold is about 1/10 of the resistance when the lamp is on and the filament heated.

A 100 ohm resistance would results in (220²)/100= 484W
for 40v @220v the operating resistance is R= 220² / 40 = 1210 ohm

 

[LvW]

Such a device can be used - for example - as a non-linear gain controlling element (with positive temperature coeff..) in harmonic oscillators. In fact, it was used by Mr. W.R. Hewlett in 1939 to stabilize the world's first WIEN oscillator.

 

[Electro Builder]

hai alexan hw u got that 1210ohm

 

[alexan_e]

P=V*I and I=V/R so you can write P= V * (V/R) = V²/R
If you solve for R then R= V²/P

V=220v
P=40W

R = 220²/40 = 48400/40 = 1210 ohm

Alex