# How to know whether to use Fleming's left hand or right hand rule?

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#1
I always get confused between the two as i dont know the conditions for each rule. Ive seen some questions that look so similar so i use the same rule on both but its always one and then the other? please help the unit 4 exam is tomorrow morning
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2 years ago
#2
left hand rule is concerned with current carrying wire being placed in a magnetic field
right hand rule is concerned with field lines around a current carrying wire given the direction of flow
in other words if they ask u to draw magnetic field lines around a current carrying wire, it will most probably be right hand rule
if they want u to state which way something moves, it will most probably be left hand rule
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#3

thanks for replying so quickly! in the question above it asks to explain whether the current will provide a force that increases the speed of the conductor. in the mark scheme theyve used both rules to show force is to the left. what would be the reason they used RHR if LHR tells you what you need to know?
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2 years ago
#4
is this a level?
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#5
yes
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2 years ago
#6
this still comes into physics in a-level! im not suprised but i got confused with the two at gcse
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2 years ago
#7
I only do GCSEs but left hand rule is to do with the motor effect whereas right hand rule is to do with the generator effect. With LHR, you're normally trying to find the direction of motion.
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#8
yeah i didnt have to do it for GCSE sooo im confused as heck lmao
(Original post by Coolkitkat23)
this still comes into physics in a-level! im not suprised but i got confused with the two at gcse
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#9
thats great thank you. also for LHR is it motion/force? and so right hand is for finding direction of current?

(Original post by iBearHQ)
I only do GCSEs but left hand rule is to do with the motor effect whereas right hand rule is to do with the generator effect. With LHR, you're normally trying to find the direction of motion.
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2 years ago
#10
(Original post by sophier59)
thats great thank you. also for LHR is it motion/force? and so right hand is for finding direction of current?
Well the question can ask you to work out either motion, field or current using either right or left hand rule - it just depends on the two values that they are give you.
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2 years ago
#11
you'll be fine
(Original post by sophier59)
yeah i didnt have to do it for GCSE sooo im confused as heck lmao
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2 years ago
#12
Fleming's left-hand rule is used for electric motors, while Fleming's right-hand rule is used for electric generators
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#13
okay thats great thank you!
(Original post by iBearHQ)
Well the question can ask you to work out either motion, field or current using either right or left hand rule - it just depends on the two values that they are give you.
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#14
thank you !
(Original post by Coolkitkat23)
you'll be fine
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