# Right hand rule and left hand rule

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Thread starter 4 years ago
#1
Which rule do you use when you're trying to find the direction of the force on a positively charged particle moving through a magnetic field? What if it's an electron? What about a current carrying conductor? Basically can someone tell me everything I need to know about these two rules? They've been confusing me for so long.
Thank you in advance!
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4 years ago
#2
You regard a moving charged particle as an electric current. If the particle has positive charge the direction of the current is the same as the direction the particle is moving but if it's a negative particle the current is the opposite direction to the movement of the particle.

The 'hand rules' take 2 'input directions' and give you one 'output directions' and the correct rule depends on what inputs you have.

for a charged particle moving with respect to a magnetic field your inputs are current (as above) and magnetic flux... the output is a force on the particle which will accelerate it... you are a putting current in a magnetic field and the output is a force...
this is equivalent to an electric motor so you use the hand rule for motors (left)

I think the confusion comes in from learning the left hand rule with 'motion' as one of the mnemonics and in particle beam type questions it's tempting to think that 'motion' of the particle is one of your 'inputs'... but because it's a charge carrying particle it's the current.
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Thread starter 4 years ago
#3
So for electrons do we use the right hand rule?
(Original post by Joinedup)
You regard a moving charged particle as an electric current. If the particle has positive charge the direction of the current is the same as the direction the particle is moving but if it's a negative particle the current is the opposite direction to the movement of the particle.

The 'hand rules' take 2 'input directions' and give you one 'output directions' and the correct rule depends on what inputs you have.

for a charged particle moving with respect to a magnetic field your inputs are current (as above) and magnetic flux... the output is a force on the particle which will accelerate it... you are a putting current in a magnetic field and the output is a force...
this is equivalent to an electric motor so you use the hand rule for motors (left)

I think the confusion comes in from learning the left hand rule with 'motion' as one of the mnemonics and in particle beam type questions it's tempting to think that 'motion' of the particle is one of your 'inputs'... but because it's a charge carrying particle it's the current.
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4 years ago
#4
(Original post by aswathy0311)
So for electrons do we use the right hand rule?
Left hand for positive and negative charged particles
BUT the current is the same direction as a positive particles velocity and the opposite direction to a negative particles velocity
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Thread starter 4 years ago
#5
OHH Alright thanks!
(Original post by Joinedup)
Left hand for positive and negative charged particles
BUT the current is the same direction as a positive particles velocity and the opposite direction to a negative particles velocity
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