# Electromagnetic Induction Project Help

1. Jun 16, 2015

### Jimmy87

Hi, trying to http://physics.stackexchange.com/questions/189766/teslas-egg-of-columbus# [Broken] Tesla's egg of Columbus for a science project ().

I have managed to cast a small rod of solid aluminium into a solid egg shaped piece of aluminium. I also have a large glass bowl that could sit inside an induction stator. However, I am unsure about how to get the correct induction stator for this to http://physics.stackexchange.com/questions/189766/teslas-egg-of-columbus# [Broken]. Does it have to be 3 phase? Or could I, for example, http://physics.stackexchange.com/questions/189766/teslas-egg-of-columbus# [Broken] this single phase induction motor (http://www.ebay.co.uk/itm/Newmans-i...260?pt=LH_DefaultDomain_3&hash=item3aac1ccadc) and take the motor out and sit the glass bowl inside with the egg on http://physics.stackexchange.com/questions/189766/teslas-egg-of-columbus# [Broken] and then plug it into the mains? My worry is plugging the stator into a wall socket, will this be safe?

Last edited by a moderator: May 7, 2017
2. Jun 16, 2015

### Hesch

What's the purpose? To make the egg spin?

With a single phase you will not have any rotational movement of the magnetic field. It will just go back and forth. With three phases ( or two ) the magnetic field will rotate because you are making a current-triangle ( an area ) wherein there is "space" for an angle and thus for an angular velocity. You cannot draw an angle within a line ( except for a fixed angle of 0 or 180° ). No space for an angular velocity.

Your single phase motor will turn because a pseudo-phase is created by means af an extra coil in series with a capacitor. This capacitor will make a current phaseshift in the extra coil, thereby making the space.
Use a safety transformer with a secondary voltage of say 32V. ( I don't know what "safety" is in US. ).

Last edited by a moderator: May 7, 2017
3. Jun 16, 2015

### Jimmy87

Hi, thanks for the info. Yeh purpose is to make the egg spin. Will I need a 3 phase stator then and connect it to a variac or something?

4. Jun 17, 2015

### Hesch

Yes, but remember that variacs are often made with only one coil, acting as both primary and secondary coil. It's a auto-transformer that does not separate the grid voltage from the secondary voltage. It is just stepping up/down the grid voltage. Use an ohm-meter to test if there is connection between the primary voltage is isolated from the secondary voltage (safety). Auto transformer: