Hello I am new here, I need help.

I have 2 rail supply (12VAC 0.7A & 24VDC).
Space is limited so they are close to sensible electronic (<4mv audio input signal).
I want to limit the electromagnetic field produced by those wires.

I have read that you could twist 2 wires (+/-) into each other (1 with the positive & the other with the return current)
So that the 2 magnetic fields cancel each others.

But how is it possible since solenoids have a bigger "external" magnetic field than straight wires ?
(by external I mean not inside the core of a solenoid)

If I understand this correctly the magnetic field inside the 2 wires twisted should cancel
but not the "external" field which is now bigger, & reach longer than the straight wire magnetic field.

 

hi frederico,
Welcome to AAC.
Is this Homework or a College assignment.?
E

 

Hello it's a custom project I am working on.
Nothing related to school just thinking about improving my design.

 

If I understand this correctly the magnetic field inside the 2 wires twisted should cancel
but not the "external" field which is now bigger, & reach longer than the straight wire magnetic field.

Why do you think that? The fields set up by the wires are opposing. They won’t be identicallly opposite everywhere but on average it will be pretty close to canceling out.

You might consider some shielding instead

 

Thank you.
Because if we want to make an electromagnet we have to create a coil and pass current trhough it.
If we would want to create the same magnetic field from a straight wire,
we would have to pass several time more current to achieve the same magnetic field.

That is why it seems counter intuitive to widen/strenghten the magnetic field, then afterward cancel it.
But I am pretty sure I miss something that is why I ask for help.

In the equations we assume the solenoid is a perfectly wound=nogap and of infinite length.
In the real world solenoids external fields are very weak compared to the inside of the solenoid. (not compared to a straight wire ?).

I am very confused. Thank you for your interest.