Question

In the "Drop Zone" ride at Canada's Wonderland, riders are dropped from a great height and then decelerated safely to a stop before hitting the ground. One possible technological application of Faraday's principle and Lenz's law is the ride's braking mechanism. If the ride is simulated by dropping a magnet with the north side down into an open copper pipe,

a) What is the direction of current flow in the pipe?

b) What is the direction of the induced magnetic field?

c) Why does this situation result in decreased acceleration of the magnet/ride? Explain well.

d) Would this situation be any different if the south end of the magnet was dropped down instead? Explain.

Answer 1

a)

Treat the copper tube as a loop of closely space wires. When a magnet falls into the loop with north face towards the loop, the flux will keep on increasing. The original magnetic field is downwards ( through the loop) , so original current must be clockwise as seen from above

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b)

As the magnet gets closer and closer, there will be change in flux. Due to this, induced magnetic field will be set up, out the the tube , this means induced current will be counter clockwise as seen from above the tube.

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C) Now, as the magnetic field of magnet interacts with copper tube, we can use right hand rule to find the direction of current produced, these are called as eddy current. These currents acts as solenoids and produce their own magnetic field. see the diagram below

so,

notice the small current loop inside the tube, that is eddy current.

These currents will set up its own magnetic field with north pole closer to north pole of falling magnet.

As we know like poles repel, this will slow down the falling magnet.

This is how it will be used to slow down the rides.

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