Ballast Resistor

[Wars37]

Where can I buy a 6volt ballast resistor ? Most sites don't specify 6 or 12 v. Are they all the same? Thank for any help.

[mcgarrett]

If you need one for a flathead Ford, try these folks.
https://thirdgenauto.com/product/new...tion-resistor/

[tubman]

Resistors are not voltage dependent; they follow Ohm's Law : In this case, R=V/I, where R=resistance (ohms); I=Current (amps), and V=voltage. To figure out what you actually need, you must know something about the circuit concerned and be prepared to do a little work.

Since you mentioned a "ballast resistor", it's probably for an ignition system. For example, for a points ignition system, with 12 volts and a coil with 1.5 internal resistance, you need a 1.5 ohm ballast resistor to obtain the desired 4 amp load across the points (3=12/4); (the 3 ohms of resistance is made up of 1.5 from the coil and 1.5 from the ballast resistor.) For a 6 volt system, no ballast resistor is required; (1.5=6/4).

Generally, doing electrical work by rote is not a good idea.

[cas3]

What are you working on would some good info.

[Seth Swoboda]

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Originally Posted by tubman

Resistors are not voltage dependent; they follow Ohm's Law : In this case, R=V/I, where R=resistance (ohms); I=Current (amps), and V=voltage. To figure out what you actually need, you must know something about the circuit concerned and be prepared to do a little work.

Since you mentioned a "ballast resistor", it's probably for an ignition system. For example, for a points ignition system, with 12 volts and a coil with 1.5 internal resistance, you need a 1.5 ohm ballast resistor to obtain the desired 4 amp load across the points (3=12/4); (the 3 ohms of resistance is made up of 1.5 from the coil and 1.5 from the ballast resistor.) For a 6 volt system, no ballast resistor is required; (1.5=6/4).

Generally, doing electrical work by rote is not a good idea.

This is great advice. I will vouch for it.