Thread: Voltage across airplane wings if carrying magnet

I know that a plane flying through the Earth's magnetic field perpendicularly will create a small voltage between the wing tips. The Earth's field is very small. If the plane were to fly through a large field, this voltage would be much higher. My question is, would it work if the plane carried a large magnet, and essentially provided its own magnetic field, or is there a fundamental problem with this plan that is related to the motion of the magnet? My physics class is curious to hear your comments.
Thanks!

Originally Posted by mhuntress

I know that a plane flying through the Earth's magnetic field perpendicularly will create a small voltage between the wing tips. The Earth's field is very small. If the plane were to fly through a large field, this voltage would be much higher. My question is, would it work if the plane carried a large magnet, and essentially provided its own magnetic field, or is there a fundamental problem with this plan that is related to the motion of the magnet? My physics class is curious to hear your comments.
Thanks!

I'll get you to come to the answer by asking another question: If I place a magnet (say, a very, very, very strong magnet) next to a conductor on a table, will I generate a voltage across the conductor? Assume that the magnet and wire are glued to the table.

Next, if I take the table -- magnet and all -- and put it into motion, will the answer change? If yes, how do the magnet and wire "know" that they are in motion?

Originally Posted by tk421

I'll get you to come to the answer by asking another question: If I place a magnet (say, a very, very, very strong magnet) next to a conductor on a table, will I generate a voltage across the conductor? Assume that the magnet and wire are glued to the table.

Next, if I take the table -- magnet and all -- and put it into motion, will the answer change? If yes, how do the magnet and wire "know" that they are in motion?

Ah, of course, relative motion. So you are saying that because there is no relative motion between the plane and the magnet it carries, there will not be an induced voltage- you can think of the magnetic field lines as moving with the wings?

another way of looking at this is if you have a coil of wire in a magnetic field as you turn the wire electricity is created. Now do the same with current already in the coil is more electricity produced?

Originally Posted by mhuntress

Originally Posted by tk421

I'll get you to come to the answer by asking another question: If I place a magnet (say, a very, very, very strong magnet) next to a conductor on a table, will I generate a voltage across the conductor? Assume that the magnet and wire are glued to the table.

Next, if I take the table -- magnet and all -- and put it into motion, will the answer change? If yes, how do the magnet and wire "know" that they are in motion?

Ah, of course, relative motion. So you are saying that because there is no relative motion between the plane and the magnet it carries, there will not be an induced voltage- you can think of the magnetic field lines as moving with the wings?

Exactly -- excellent! You get an A+.

If we were able to induce voltage this way, it would be an absolute velocity detector, which would violate Galilean relativity, to say nothing of Einstein's.

Well done!