Naked Science Forum

General Science => General Science => Topic started by: mystikalneon on 20/06/2007 14:12:55

Title: Determining Poles without Using the Sun
Post by: mystikalneon on 20/06/2007 14:12:55

Hi again!

Sorry for posting 2 topics within such a short time. Hopefully you people don't mind!

ok here's my next question.

Without using the Sun as a reference how can you determine the poles of the compass, supposing that the compass hasn't got the poles engraved on it yet. There are some items that you're given to use, they are a bare piece of copper wire, a flashlight, a dry cell and of course a compass.

Thanks in Advance!
Matthew

Title: Determining Poles without Using the Sun
Post by: another_someone on 20/06/2007 15:42:27

Quote from: mystikalneon on 20/06/2007 14:12:55

Hi again!

Sorry for posting 2 topics within such a short time. Hopefully you people don't mind!

ok here's my next question.

Without using the Sun as a reference how can you determine the poles of the compass, supposing that the compass hasn't got the poles engraved on it yet. There are some items that you're given to use, they are a bare piece of copper wire, a flashlight, a dry cell and of course a compass.

Thanks in Advance!
Matthew

You are welcome to start as many topics as you wish, so long as they are pertinent to the site.  Two is but a small number compared to that which some others have indulged in.

I assume you lack of reference to the Sun would infer (although you clearly have not stated) that one also has no reference to the pole stars, or other celestial bodies.

That you explicitly do state that we are provided with dry cells and wire would infer to me that you expect us to generated our own magnetic field by passing a current down the wire, and use that to calibrate the compass.

Title: Determining Poles without Using the Sun
Post by: mystikalneon on 20/06/2007 16:08:29

hm i got the idea of generating a magnetic field using the dry cell, but is there a way which Flemings Left-Hand Rule come in? or the Right Hand Prediction Method?

Here's my attempt at the solution, not sure whether my usage of the left and right hand rule is correct though.

Firstly, turn on the flashlight and shine it on the face of the compass such that the points are visible. Next generate a magnetic field by connecting the copper wire to the dry cell. Place the compass close to the wire, the compass needle should be perpendicular to the copper wire, following the Right-Hand Rule, predict the direction of the magnetic field. By using Fleming’s Left Hand Rule, it can be deduced that the needle pointing in the direction of the index finger is the North-Pole and the needle pointing the opposite direction is the south pole.

Thanks!

Title: Determining Poles without Using the Sun
Post by: lyner on 24/06/2007 11:46:40

It really confused me, at School, that the 'North Pole' of a magnet is a 'North - Seeking' pole - it will point north.  So the Earth's South pole, is really a North  (seeking) Pole. For what it's worth.
Rather than Flemming's rule, I think the  Corkscrew rule is the one to use for your problem. The field lines around a straight conductor carrying current  go clockwise around the wire - looking in the direction the current flows - like when using a corkscrew. The 'N' of the compass would point in the direction of these lines. The sense of the current flow would be from + to - terminal.