# Homework Help: Simple electric motor

1. Jul 24, 2012

### alicia113

ok, so i have drawn a diagram for 43 and i would like to know if i have done it correctly.. i believe the rotation should go the other way. Also can someone help me with the paragraph to wrtie about it

and for the other question, does it have something to do with the magnetic field causing the wires to vibrate and give off a faint buzzing noise. If so could someone please help me explain it better, thanks.

2. Jul 24, 2012

### alicia113

and from what i know the current flows from S to N so my rotation i believe is wrong and that is how the motor goes in the direction

3. Jul 24, 2012

### pgardn

I think you might be getting current and the magnetic field confused.

1. Do you know (by convention) which direction your magnetic field points in your drawing?
(left to right or right to left?)

2. Do you know which way the current is flowing (conventional) in your drawing of... lets use the part of the wire on the left hand side of your drawing, the straight part closest to the North Pole of your magnet?

3. Do you know the right hand rule that allows you to find the direction of the Force on the part of the wire mentioned in #2?

4. Jul 24, 2012

### alicia113

yes i know the right hand rule.................................. and i do not understand number 1 and 2 :(

5. Jul 24, 2012

### alicia113

is my current flow wrong than ??

6. Jul 24, 2012

### alicia113

so becasue it flows from south to north and when using the right hand rule.. my direction of it rotating should be the opposite way?

7. Jul 24, 2012

### pgardn

Current flows from + to -

The permanent magnets you have drawn produce a magnetic field between them yes?

Which way does the field point? N to S or S to N...? What is the convention, in other words, what do we all agree on about the direction of the magnetic field based on your drawing and the poles (N and S)?

8. Jul 24, 2012

### alicia113

s to N?

9. Jul 24, 2012

### pgardn

Out of North into South. Thats the rule we have all agreed upon. N to S.

So in the part of the wire that is closest to the North pole that you have drawn going into the page, which way is the force on that piece of wire? You now need to use the right hand rule.

You know the direction of the magnetic field, you know the direction of the current in that piece of wire, so which way is the force on the wire at that particular orientation?

10. Jul 24, 2012

### alicia113

I don't know how I find that. All my book gives me is the right hand rule and talkes about the parts of a motor.

But okay so my current flow goes from north to south. so my diagram is rotating the correct way. as the amateur spins the direction of the current in the loop of wire keeps reversing as the coul reaches a position where the force is no longer produced as a rotation.

11. Jul 24, 2012

### alicia113

And by using the right-hand rule, it shows the direction of the Motor spinning. Because as you fold over your hand your right hand the direction goes from north to south so that is the way it rotates

12. Jul 24, 2012

### pgardn

Current is used to describe the flow of electricity, not magnetic fields.

The magnetic field points from Left to right in your drawing, now which way does the electric current flow in the piece of wire that you have drawn next to the North pole of the magnet?

13. Jul 24, 2012

### pgardn

Alicia you probably need to find a better book and talk to your teacher.

You seem a bit weak on this stuff.

I am going to leave you with this applet that shows the physical process. I gotta go to work.

http://www.walter-fendt.de/ph14e/electricmotor.htm

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