Faradays experiment (1 Viewer)

[speersy]

In success one p 26 there is a multi choice which asks which way the wire will rotate in faradays famous experiment when the reservoir of Hg is negative and the rod that rotates is conected to the positive terminal.

I have read their explanation for the answer and still dont get it.
Like i can't add up the magnetic fields

 

[helper]

Which way is the magnet?

 

[speersy]

North Pole facing up

 

[helper]

Right Hand rule
Current down with thumb

Fingers going out of magnet to the side, as it is the magnetic field where it is bending that is causing the force.

Force, is palm is clockwise.

 

[speersy]

yep you are right about the directions however i cant understand what you mean. The magnetic fields are going perpendicular to each other.

 

[helper]

Thin of the magnetic field
_ _
/ || \
| N |

Only the section perpindicular to wire will have an effect. This is the section at the top going out _.

So the magnetic field is going horizontally away from the magnet.

Those two lines should be above the N

 

[speersy]

yep i get that but dont know how this gives the direction of rotation
Is the direction for these types of questions just the way the magnetic field goes around the wire.

 

[helper]

No.

Do you normally use the right hand palm rule?

 

[speersy]

yeah i use the right hand rule in which you point your fingers in the direction of the current and your fingers curl in the direction of the magnetic field around the wire.

 

[helper]

Which rule do you use to find the direction of a force on a current carrying wire?

 

[speersy]

sorry, yeah i use the right hand palm rule. u point your thumb in direction of current and fingers in direction of magnetic field. Your palm shows the direction force

 

[helper]

OK using that rule.

Point your thumb from positive to negative. That is down the wire.
Your fingers need to point out from the North pole to the edge of the dish. IT doesn't matter which side you start.
Your palm will now point in the direction of the force. Follow your palm around the wire to obtain the direction

 

[speersy]

I think i have it now.
So i point my fingers towards the negative wire that is in the mercury, while pointing my fingers up in the air (assuming i put my hand on the right side of the magnet) . My palm now points in the direction of the force. I dont think thats what you were explaining as i did not use the magnetic field around the wire.

 

[helper]

Your not using the magnetic field around the wire, rather a straight application of the motor effect.

Eg
---|--->
---|--->
---|--->

Assume current is flowing towards the bottom of the screen.
Right hand rule tell us the force is pushing the wire out.

<---|---
<---|---
<---|---

Right hand rule tell us the force is pushing the wire into the page.

The first diagram is when your wire is on the right of the magnet.
The second on the left.
The resultant is a clockwise motion.

Remembering were only using the perpindicular area at the top of the magnet.

 

[speersy]

holy crap i have got it!
You can sleep well tonight buddy knowing you taught me this and i got an extra mark in the exam tomorrow. lol