ohm's law/voltage help

[M0nkeyb0Y]

I've dug out an old fan resistor and I'd like to work out what volts it'll resist to, it's code is GREEN, BLUE, BLACK,GOLD, which I think is 56 Ohms...

I said think...

Ohm's law is V=IR... I think, but I can't figure out what the current would be

God, I did physics A-level, and now am getting confused by this!

Blimey, any help??? What voltage would it give me?

[arthurleung]

I've dug out an old fan resistor and I'd like to work out what volts it'll resist to, it's code is GREEN, BLUE, BLACK,GOLD, which I think is 56 Ohms...

I said think...

Ohm's law is V=IR... I think, but I can't figure out what the current would be

God, I did physics A-level, and now am getting confused by this!

Blimey, any help??? What voltage would it give me?

A resistor is a resistor, you put them in series to give you a voltage split based on the relative resistance of the resistors.

The current is depending on the voltage being fed through it.

You could be feeding 56V into it which the 56 Ohms resistor give you 1A current. Or you could put 560V into it and it will give 10A current.

[M0nkeyb0Y]

A resistor is a resistor, you put them in series to give you a voltage split based on the relative resistance of the resistors.

The current is depending on the voltage being fed through it.

You could be feeding 56V into it which the 56 Ohms resistor give you 1A current. Or you could put 560V into it and it will give 10A current.

thanks - but if it's in a PC?

[pipTheGeek]

thanks - but if it's in a PC?

It still depends on what supply voltage (There are 3 voltages easily available from the PSU.) it is given and what else is in the circuit. Can you be a bit more specific?

[Biscuit]

then nothing changes...

you always need 2 values to work out the other using ohms law, it doesnt matter if its in a PC or a microwave or anything, electricity is electricity.

[watercooled]

Yeah you need two values to get a third out. In your case you need a voltage...

[Biscuit]

from a PSU you are delivered wither 12v 5v or 3.3v depending on which componant its going to. I think fans are 12v usually.

[watercooled]

With a 56ohm resistor with a 12v input you should get roughly 7v out when using a fan but that will vary a few volts depending on how much current it draws. Ensure it's at least a 1w resistor though or you risk overloading it.

[M0nkeyb0Y]

With a 56ohm resistor with a 12v input you should get roughly 7v out when using a fan but that will vary a few volts depending on how much current it draws. Ensure it's at least a 1w resistor though or you risk overloading it.

from a PSU you are delivered wither 12v 5v or 3.3v depending on which componant its going to. I think fans are 12v usually.

Thanks guys

[arthurleung]

Thanks guys

If the fan is not a power hog, then just wire the negative side to the 5V line. That will give you 12V - 5V = 7V.

If you still want to do the resistor way, check the fan you are using. if it says 12V 0.1A it will use 0.05A at 6V. You'll need a 120 Ohms resistor. Wrong resistor wrong voltage. It is unlikely that the resister will overload if its hooked to a relatively low power fan.