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# Flemings left hand rule vs Flemings right hand rule

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1. This may seem extremely obvious, but I'm really starting to get confused by when to use which one. My understanding is that you use the right hand rule when the force is being applied to the wire/coil (by hand for example), and you use the left hand rule when the force is a result of the field/s. But after thinking about it some more, I'm not sure how correct that is.

Could someone please tell me the difference between the two first of all, and when to use which one?

2. (Original post by ludd-sama)
This may seem extremely obvious, but I'm really starting to get confused by when to use which one. My understanding is that you use the right hand rule when the force is being applied to the wire/coil (by hand for example), and you use the left hand rule when the force is a result of the field/s. But after thinking about it some more, I'm not sure how correct that is.

Could someone please tell me the difference between the two first of all, and when to use which one?

Fleming's left-hand rule tells you the direction of the force a current-carrying wire experiences if it is placed in an external magnetic field.

The right-hand rule tells you the direction of the induced current when a conductor moves in a magnetic field (the direction of the thumb in this case represents the direction of motion).

Are you familiar with Lenz's Law? This law states that an induced current always flows in a direction such that it will oppose the change that produced it.

This makes sense if you consider the left and right hand rules: if the conductor was moved upwards (the direction of the thumb in the diagram above) it would induce a current in the direction of the second finger. We now of course have a current-carrying wire in a magnetic field, so it's going to experience a force. Which way will the force act? From the left hand rule you can work out that if the current is moving to the left, then the force is acting downwards, meaning it is acting in the opposite direction to the upwards movement of the wire.

Hope this helps.
3. (Original post by ludd-sama)
This may seem extremely obvious, but I'm really starting to get confused by when to use which one. My understanding is that you use the right hand rule when the force is being applied to the wire/coil (by hand for example), and you use the left hand rule when the force is a result of the field/s. But after thinking about it some more, I'm not sure how correct that is.

Could someone please tell me the difference between the two first of all, and when to use which one?

I use this method for remembering:

Right hand rule: Generators/dynamo's (produce current from an applied force).

Left hand rule: motors/solenoids. (produce force from an applied current).
4. (Original post by Ollie231213)
The right-hand rule tells you the direction of the induced current when a conductor moves in a magnetic field (the direction of the thumb in this case represents the direction of motion).

.
So, the thumb represents the motion of the force from the motor effect not the force from the induced current, right?
5. (Original post by uberteknik)
I use this method for remembering:

Right hand rule: Generators/dynamo's (produce current from an applied force).

Left hand rule: motors/solenoids. (produce force from an applied current).
Hmm, that might actually prove helpful to remember, thanks
6. (Original post by ludd-sama)
So, the thumb represents the motion of the force from the motor effect not the force from the induced current, right?
No, the thumb represents the direction of movement which causes the induced current. The thumb in the left-hand rule tells you the direction of the force caused by the induced current.

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