120v coil. need only 3 amps? How do i do that?

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Thread Starter

ElectromagnetNewbee

Joined Jul 13, 2014
69
I just rolled a 120Volt Coil. I am using it as an electromagnet. 24Gage wire.

I want 3 amps ONLY.

what do i use to control the ampers? do i just use a couple resistors or what?
 

tcmtech

Joined Nov 4, 2013
2,867
I would investigate the or what end more myself like the concept of Ampere turns and wire length VS its resistance.
 

Thread Starter

ElectromagnetNewbee

Joined Jul 13, 2014
69
Use Ohms law If you know the voltage and current X=V/I
is Ohms law all that needs to be addressed for AC current? I just want to make sure my 20 amp breaker does not 'break'. So if the coil is designed for 120 volts and 3 amps, then hooking it up to the ac wall outlet it will only push 3 amps? is this correct? for future reference, are amps allows governed by resistance? so i can use resistance to get my required amps? i just need to confirm.
 

MaxHeadRoom

Joined Jul 18, 2013
28,698
No, the resistance of a AC coil is generally very low, it is the Inductive reactance that limits the current, also as I mentioned, a method of retaining the attracted part will usually have to be designed in as it will either buzz like crazy or drop the attracted part.
The current is also much higher until the attracted armature or object is on the pole piece.
What is the purpose of the electro magnet?
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
28,698
is Ohms law all that needs to be addressed for AC current? I just want to make sure my 20 amp breaker does not 'break'. So if the coil is designed for 120 volts and 3 amps, then hooking it up to the ac wall outlet it will only push 3 amps? is this correct? for future reference, are amps allows governed by resistance? so i can use resistance to get my required amps? i just need to confirm.
You still have to confirm if you intend using purely AC or use a rectifier for a DC version?
If AC the DC resistance of the Coil does not come into it, in fact it is a detriment.
It will also have a high inrush current.
Max.
 

Thread Starter

ElectromagnetNewbee

Joined Jul 13, 2014
69
i want to use AC current from the wall. 120volt. i built the circuit using ohms law. this should be the same for both DC and AC correct? ohms law works with both correct?
 

MaxHeadRoom

Joined Jul 18, 2013
28,698
i want to use AC current from the wall. 120volt. i built the circuit using ohms law. this should be the same for both DC and AC correct? ohms law works with both correct?
No , read post #7 and look up inductive reactance.
An AC electromagnet has very low resistance, the current is limited by the value of the inductance on 50/60hz, and is Inductive reactance in Ohms.
If you calculate the resistance as for DC, when you come to use it on AC the current and magnetic effect will be a lot lower
Max.
 

Thread Starter

ElectromagnetNewbee

Joined Jul 13, 2014
69
so i just plugged in my newly rolled electromagnet coil into 120v AC wall. wow! way different than DC!

using DC I get a 'north' and a 'south' pole magnetic field. using AC I do not. will using a rectifier give me both north and south pole fields? how do i get a the north and south pole back like when using DC?
 
Get an LCR meter and measure the inductance and the resistance of your coil.
The average amperage will be [85/(Resistance + 60 * 2pi * inductance)]

However, I suggest not messing with the mains power and trying your experiments on lower voltages.
 

bertus

Joined Apr 5, 2008
22,278
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