Lenz's Law A2 Practical
I have a qualitative practical on Lenz's law tomorrow, and I'm struggling to understand the physics behind why there is magnetic braking. The practical is called 'Dropping a magnet through a copper pipe'. Has anyone done this practical, or understand all the relevant principles which could be discussed with regards to: magnetic braking, eddy currents and magnetic fields, taking into account Lenz's law?
Thanks in advance
Thanks in advance
Original post by Rhodopsin94
I have a qualitative practical on Lenz's law tomorrow, and I'm struggling to understand the physics behind why there is magnetic braking. The practical is called 'Dropping a magnet through a copper pipe'. Has anyone done this practical, or understand all the relevant principles which could be discussed with regards to: magnetic braking, eddy currents and magnetic fields, taking into account Lenz's law?
Thanks in advance
Thanks in advance
This is useful
http://www.bbc.co.uk/bang/handson/magneticcopper.shtml
and this thread
http://www.thestudentroom.co.uk/showthread.php?p=40111788
Just revised this 
Say you have a long copper coil and a bar magnet.
Lenz's Law states that the direction of the induced current will oppose the change that caused it.
As you drop the North end of the magnet into the coil, a current flows so to produce a North pole at the end of the coil that the bar magnet is entering. This happens to repel the bar magnet slowing it's velocity down. The solenoid rule states that this will cause an anticlockwise current in the coil. (N = aNticlockwise, S=clockwise)
Once the magnet is halfway into the coil (ie, the North end is fully within the coil and the south end is just about to enter) the current flips so that it is now going clockwise and a South pole is induced in the top end of the coil to repel the south pole's motion.
This state also means that when the North pole begins to exit the coil it is also being repelled as the bottom of the coil is now North.
When the bar magnet is halfway out of the coil (ie, the North end is fully out and the South end is just about to exit) the current flips once more meaning that the current flows anticlockwise (we're still looking from the position of being above the top end of the coil) and a South pole is induced in the bottom of the coil opposing the bar magnet's exiting from the coil.
Other relevant factors include but are not limited to:
The strength of the magnet (B)
The number of coils (N)
Say you have a long copper coil and a bar magnet.
Lenz's Law states that the direction of the induced current will oppose the change that caused it.
As you drop the North end of the magnet into the coil, a current flows so to produce a North pole at the end of the coil that the bar magnet is entering. This happens to repel the bar magnet slowing it's velocity down. The solenoid rule states that this will cause an anticlockwise current in the coil. (N = aNticlockwise, S=clockwise)
Once the magnet is halfway into the coil (ie, the North end is fully within the coil and the south end is just about to enter) the current flips so that it is now going clockwise and a South pole is induced in the top end of the coil to repel the south pole's motion.
This state also means that when the North pole begins to exit the coil it is also being repelled as the bottom of the coil is now North.
When the bar magnet is halfway out of the coil (ie, the North end is fully out and the South end is just about to exit) the current flips once more meaning that the current flows anticlockwise (we're still looking from the position of being above the top end of the coil) and a South pole is induced in the bottom of the coil opposing the bar magnet's exiting from the coil.
Other relevant factors include but are not limited to:
The strength of the magnet (B)
The number of coils (N)
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