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Probably rather trivial, but it's thrown me: Physics question

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So if the magnetic fields cancel each other is it attractive and if the magnetic fields add to each other is it repulsive?
gangsta316 - Pretty much, yeah.

The way I think of this problem is by way of the Lorentz forces.

Consider the wire on the right. By the right-hand grip rule, the magnetic field generated by a current moving 'upwards' on a page will be going out of the page everywhere to the left of the wire (and into the page everywhere to the right of it.)

Now consider the wire on the left, under the influence of the magnetic field of the wire on the right. Remember that this magnetic field is going out of the page, and the current in this wire is going 'upwards' on the page. We find the direction of the force on this wire by Fleming's Left Hand Rule. The field is vertically out of the page, the current is 'up' the page, so if you've done this right, your thumb should be pointing towards the wire on the right.

This happens in exactly the opposite way when you consider the magnetic field from the wire on the left on the current of the wire on the right.

And so the wires come together. Attraction.
But on the left wire, the field goes out of the page on the left and into the page on the right. So to the right of this wire (because we want to find what's happening between the wires) we use Fleming's left hand rule with the field down and the current up, and the force is away from the wire.
The left wire generates a field into the page on the right.
The right wire sits in this field, carrying a current up the page.
FLHR says that the direction of the Lorentz force on the right wire will be left.
Adje
The left wire generates a field into the page on the right.
The right wire sits in this field, carrying a current up the page.
FLHR says that the direction of the Lorentz force on the right wire will be left.


I see. You have to find the effect of the field of the other wire. Thanks.
Reply 25
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Zebrahead
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Hey all, I'm back again ^^


Thanks very much, I havent been on all evening but the comments since last night have all been great!

It's a lot clearer now and I think im really starting to get to grips with all of this ^^

Hopefully i'll have it all figured by the exam! ^^

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