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Magnetic field

splitter2017

Can anyone help me with question 2 please. I thought it was due to the natural frequency of the wire not matchign the driving frequency of the magnetic field and I said adjust the tension so they match.

But apparently it is something to do with the position of the force at nodes/anitnodes?? Surely the magnetic force is applying force to all points along the wire upwards?

My question is ii 2: https://ibb.co/j09WTT
Previous context: https://ibb.co/m2rya8
Mark scheme: https://ibb.co/gvJuF8

Reply 1

Sir_Malc

If you look at fig 5.1, It looks like the magnets are only acting across 6.0cm of the wire. So the magnets are only acting on a small portion of the total length of wire.

It's only this 6.0cm portion of wire that experiences the force due to the magnetic field, not the whole length of wire.

As this small portion is now at a nodal point in part 2 ii, it will not be able to oscillate the wire much hence the smaller amplitude.

Hope some of that makes sense, maybe someone else can expand further.