The Ford Barn - View Single Post - I need some help- circuit breaker question 6V vs 12V

Mike51Merc · 09-04-2011, 07:48 AM

Double the Voltage = Half the Current (AMPs)
Half the Voltage = Double the Current

Ohm's Law E = IR (look it up) tells us that devices that work at half the voltage pull twice the current, and vice versa. This is why 6 volt cars have heavier wires than 12 volt cars; they need twice the current (amps) to make the lights shine as brightly as they do on a 12 volt car.

What that means is that if a device with a fixed output (lightbulb candlepower, electric motor RPMs, etc.) pulls 14 amps at 6 volts, they will only need 7 amps at 12 volts to do the same job.

The bottom line is that on a 12 volt system, you'd want a circuit breaker (and/or fuses) with HALF the rating of your 6 volt ones.

Radio Shack carries circuit breakers that will do the job. They even look like the original ones.

09-04-2011, 07:48 AM	#5
Mike51Merc Senior Member Join Date: May 2010 Location: Northeast Pennsylvania Posts: 1,582	Re: I need some help- circuit breaker question 6V vs 12V Double the Voltage = Half the Current (AMPs) Half the Voltage = Double the Current Ohm's Law E = IR (look it up) tells us that devices that work at half the voltage pull twice the current, and vice versa. This is why 6 volt cars have heavier wires than 12 volt cars; they need twice the current (amps) to make the lights shine as brightly as they do on a 12 volt car. What that means is that if a device with a fixed output (lightbulb candlepower, electric motor RPMs, etc.) pulls 14 amps at 6 volts, they will only need 7 amps at 12 volts to do the same job. The bottom line is that on a 12 volt system, you'd want a circuit breaker (and/or fuses) with HALF the rating of your 6 volt ones. Radio Shack carries circuit breakers that will do the job. They even look like the original ones.