# Resistor uses

Discussion in 'General Electronics Chat' started by Lightfire, Jun 3, 2011.

1. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Hello,

May I ask if resistor can be used to limit up the voltage and current acrossing in the lamp.

Ok.

The lamp ratings are 6V/0.5A/3W
and the battery ratings are 12V/12AH

thanks
Lightfire

Dec 26, 2010
2,147
302
Yes, you could use a series resistor, but it would be an inefficient way to light your lamp. You would need to drop half of the 12V in a resistor to get down to 6V across the lamp. This would mean the resistor would convert half of the power supplied by the battery to heat, which probably you do not want.

The resistor is required to drop 6V at 0.5A, so according to R=V/I its value must be 6V/0.5A=12Ω. The resistor power dissipation is 6V*0.5A=3W, so at the very least a 3W rated resistor is required. A 5W resistor might be better, and would allow for the fully charged battery being a bit over 12V.

Alternatively, you might prefer to use two equal wattage 6V bulbs in series. The second bulb would give more light, instead of wasting 3W all as heat.

Lightfire likes this.
3. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Thanks!!!!!!!!

4. ### Wendy Moderator

Mar 24, 2008
21,341
2,918
Well, are you going to tell the folks about the packge?

Oct 5, 2010
690
21
No, I won't.