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current electricity help. watch

thank you so much.

The question is:

Efforts are being made to increase the efficiency of railway networks. One way of doing this is to reduce the resistive forces experienced by trains. This can be achieved by levitating the train using very large electric currents which pass through superconducting materials to produce strong magnetic fields. It is important that the train remains at a fixed distance above the rail.

As a first-rate investigation of this effect, an alternating current 'I', is passed through a coil placed at the base of a vertically mounted iron rod. An alumininum ring is placed over the rod. When the coil is energised, the ring rises to a stationary position above the coil.

Design an experiment to investigate how the coil current needed to raise the ring to a fixed distance above the coil varies with the load supported by the alumininum ring.

You should pay attention to:
(a) a method of attaching the ring,
(b) the procedure to be followed,
(c) possible difficulties which may be encountered.

Thank you!
2. Base it around

F = Flux Density x Current x Length Of Wire (F=B x I x l)

F= mg

The force of the magnetic field has got to be equal to the weight of the aluminium ring to get it to hover.

So

mg = BIl

mg/Bl = I

Basically the current depends on the mg of the mass on the ring divided by the flux density and length of wire.

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