# Lenz' Law / Eddy Currents

1. Dec 22, 2015

### ljfe

I had the idea of making an hourglass timepiece employing lenz's law using a magnet and copper tube (or copper bars for visibility).

Any idea how accurate my hourglass will be? I know Lenz's law is effected by temperature (not sure by how much).

If I drop a small magnet drop through a small thick walled copper tube, would that would give me the longest fall time? I think i read somewhere that thinner magnets would fall slower

Last edited: Dec 22, 2015
2. Dec 27, 2015

### jambaugh

Lenz's law itself is not a function of temperature, but the net effect you describe is a function of the material's resistance which in turn is a function of temp. Recall that for zero resistance (super conductor e.g.) you would get no movement and the magnetic is levitated. The thing to calculate I believe for you is the energy dissipated as resistance heating relative to the potential energy of the object. You'll want to control the resistance in the copper, so very pure, phone-line grade copper? I guess.

Or if you can get your hands on some high purity \$ilver...

3. Dec 27, 2015

### ljfe

Thanks for the reply. is 1/4in C110 plates good? I wonder how magnet size would effect it? I ordered really small magnets