Why does copper pipe slows the falling magnet and not accelerate it?
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If you haven't already watched "World's First Electric Generator - Veritasium",
you should watch it. When we let a magnet fall through a copper pipe, it is
slowed down by the induced electric current which creates a magnetic field that
resists the movement of the magnet.

The magnet's magnetic field can induce current in the pipe in two directions,
one is that which will accelerate it and the other which will slow it down.
According to Lenz's Law, the direction of the current induced in a conductor by
a changing magnetic field is such that the magnetic field created by the induced
current opposes the initial changing magnetic field.

Why is the converse false?
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Assumption: Law of Conservation of energy is true

Let's say that the induced current is in the direction that will accelerate the
falling magnet. That breaks the Law of Conservation of energy! We just made a
free energy generator that makes energy out of nowhere.

How?
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Rotate the pipe and make it horizontal and now remove the earth from below, or
just ignore the earth's gravity. Take the magnet and push it inside the copper
pipe and it shall go on forever. When we push the magnet we are changing the
number of field lines that pass through it which induces current in the pipe
and now according to our assumption in previous paragraph that the induced
current will accelerate the magnet, the magnet should never stop and should go
on forever but we only put a finite amount of energy in the system and it
should stop after a while if the Law of Conservation of energy is true.

There is nothing to stop it and so it won't stop, how does this break the Law
of Conservation of energy?
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Yes it should not stop if there is nothing to stop it but it should not
accelerate either. In this case it's getting accelerated, where is that extra
energy coming from?

This proves why the copper pipe slows the falling magnet and not accelerate it.
Lenz's Law hold true in every case, the conducting metal will want the number
of magnetic field lines that pass through it to not change and remain the same.

An Interesting Application: Electric brakes
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We can attach metal drums to car wheels and cover it around with powerful
electromagnets and when we turn on the electromagnet and it will stop the car.
The number of field lines that pass through the metal drum will change because
it's rotating and they don't want that change but the electromagnet is fixed so
it will have to stop itself.