# Homework Help: Direction of Lorentz force

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1. Sep 18, 2016

### physicsmaths1613

• Member advised to use the homework template for posts in the homework sections of PF.
Generally we use the left hand rule - (if index finger shows velocity, middle finger shows magnetic field, the thumb points towards force). Recently I also came across a left hand rule for lorentz force- Using your right-hand: point your index finger in the direction of the charge's velocity, v, (recall conventional current). Point your middle finger in the direction of the magnetic field, B.

Your thumb now points in the direction of the magnetic force. Generally left hand rule is used for determining the direction of induced current in a conductor placed in a magnetic field. Are both of these rules given above correct?Can we use any of them for determining the direction of lorentz force?

2. Sep 18, 2016

### Simon Bridge

... why don't you compare them and see?

3. Sep 22, 2016

### rude man

I would stick with the right-hand rule and let the signs take care of phenomena such as the direction of induced current in a conductor placed in a magnetic field.

4. Sep 22, 2016

### lychette

I think this is wrong !
First finger is field, middle finger is velocity and thumb is force....I may be wrong !!

5. Sep 22, 2016

### Simon Bridge

This is how I learned it for deflection of a wire in a magnetic field...
First finger is the Field
Second finger is the Current
Thumb is the movement

So for force on a charge, current is the same direction as the velocity of a positive charge (reverse for negative charges)
The thumb becomes the force.

6. Sep 23, 2016

### lychette

I agree..I was not wrong