Originally Posted by trekker pete

got a question about something I have heard here multiple times concerning LED/halogen bulbs.

I keep hearing that voltage determines brightness in a halogen and current in an LED.

Way back when, in basic electricity and electronics school in the navy, I was taught Ohm's law. Ohm's law states in a DC circuit, current is a function of voltage and resistance. I=E/R I being current, E, voltage and R resistance.

A halogen lamp has a constant resistance, as far as I know. Therefore, as the voltage increases, so will the current. So, you could say it is a voltage controlled device, but, it is the increase in current that actually causes the increased brightness.

I'm a bit more fuzzy on LEDs. Do they vary their resistance as the voltage changes? Just curious. Thanks.