Drop magnet here

Comments

3 responses to “Drop magnet here”

1. 

   bob sykes

   February 28, 2014

   It’s repulsion. The magnet induces a current and counter magnetic field in the pipe.

2. 

   Amiable Dorsai

   February 28, 2014

   Magnetic repulsion and attraction (while it’s in the pipe). This is Lenz’s law in action. Wave a magnet near a conductor and the changing magnetic field will induce an electrical current. The current will create its own magnetic field, which will be in a direction to oppose the change caused by the original change. So as you drop the magnet into the pipe, the pipe experiences a change in magnetic field. This induces a current whose magnetic field is such as to oppose the encroaching field, so the magnet is repelled. As it leaves the pipe, the currents induced are such as to create a magnetic field that “tries” to hold the magnet back.

   Since the pipe has resistance, the energy in the induced currents is eventually dissipated as heat, so the induced field isn’t enough to hold the magnet still, but if you substituted a superconductor for the copper, the magnet could hang indefinitely.

3. 

   Neil

   March 1, 2014

   Look up “eddy current”. The bane of motor designers, but apparently pretty cool on YouTube.