A fun (but not particularly safe) magnetism demonstration is the jumping ring. S

Question

A fun (but not particularly safe) magnetism demonstration is the jumping ring. Start with an electromagnet that is off - i.e., no current is flowing in it, so it is producing no magnetic field. Rest a conducting ring on top of the electromagnet as shown. When you turn the electromagnet on, the ring jumps into the air. Suppose the field produced by the electromagnet, when it is on, points upward and outward as shown, and gets weaker as you go farther above the electromagnet. The ring jumps because the change in magnetic field induces a current in it. In what direction is the net magnetic force on that current? The induced current produces its own magnetic field. At the center of the ring, does that field point up or down? If the ring isn't oriented precisely horizontally, would the magnetic force tend to turn it so that it orients itself more horizontally or more vertically? Do the magnetic forces tend to stretch or compress the ring? Which way does the induced current flow around the ring? If we ran current the other way through the electromagnet, it would produce a magnetic field that points down and in instead of up and out. Would the ring still jump? Explain your answer.

Explanation / Answer

a)

The way the ring negates the change is by generating a magnetic force which counteracts the magnetic force manifesting in the coil. Then, the coil's magnetic force and ring's magnetic force repel each other. on the coil current the force direction is perpendicular on the current.

b) it will be upword

c) The ring jumps high according to this magnetic repulsion. Hence The magnetic force tend to turn the coil horizontally.

d) Yes it will tend to compress the spring since it acts on both sides.

e) it will be in opposite direction to the current in the spring.

f) it wont jump since the magnetic force that induced current generating a magnetic force which attracts the magnetic force manifesting in the coil. Hence no jumping

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