Induced Voltage

[Shark 774]

This question is from iTute 2009: (see attached)

Obviously if there is no magnetic force acting on the loop then it's acceleration will be constant, due to gravity. In A, C and D there charges (electrons in the wire) are moving in a direction that is not parallel to the field, hence they will experience a force (if that's not clear then watch this: http://www.khanacademy.org/video/magnetism-12--induced-current-in-a-wire?playlist=Physics).
In B the wire is moving parallel to the field, hence this is the only one that experience no magnetic force hence this is the only one that has a constant acceleration.

However, iTute says that none of them will experience a magnetic force.

What do you guys think?

[xZero]

But its just a loop of wire, there's no current/induced current flowing in it

[Shark 774]

But its just a loop of wire, there's no current/induced current flowing in it

Moving a wire (even with no current in it) through a uniform magnetic field produces a force on the wire. Think of the formula F=BQv. As long as there is a relative motion between the particles and the field (and this motion is not parallel to the field) then there will be a force.

[xZero]

Hmmkay lets follow your logic then, is the force by the magnetic field constant? If it is then acceleration is constant even tho 1 may be bigger than the other?

[Shark 774]

Hmmkay lets follow your logic then, is the force by the magnetic field constant? If it is then acceleration is constant even tho 1 may be bigger than the other?

No the force will not be constant. The wire is accelerating due to gravity, i.e. it's speed is increasing and since the force is relative to speed (F = BQv) the force is increasing, hence the acceleration is not constant.

[xZero]

okay my last attempt to explain itutes answer. If you assume the wire is neutral then F=qvB will be 0. Otherwise vce physics prob assume that in this scenario F would be 0 much like how you can't go from n=2 to n=3 etc.

note: im not awesome with electrostatic/magnetic shit, sorry couldnt help you much with it

[Shark 774]

okay my last attempt to explain itutes answer. If you assume the wire is neutral then F=qvB will be 0. Otherwise vce physics prob assume that in this scenario F would be 0 much like how you can't go from n=2 to n=3 etc.

note: im not awesome with electrostatic/magnetic shit, sorry couldnt help you much with it

What do you mean "if the wire neutral"?

Note: Not a problem, thanks for trying.

[Aurelian]

You may be better off considering each side of the loop as a single wire, and determining the current induced in each part.

You will find that they all cancel out =)

I hope that helps!

[Shark 774]

You may be better off considering each side of the loop as a single wire, and determining the current induced in each part.

You will find that they all cancel out =)

I hope that helps!

That makes enough sense, but I still can't see any flaws in my argument. You can treat the wire as if it is just a bunch of electron that are falling to earth due to gravity. And so on as I said above. Either way, I think this question is way beyond unit 4 physics. Trust iTute to put in a question like that