# Magnetic flux lines: Left-hand or Right-hand rule?

Discussion in 'Feedback and Suggestions' started by selred82, May 30, 2008.

1. ### selred82 Thread Starter New Member

May 30, 2008
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In Vol. I Chap. 14 under Electromagnetism, it states that "A simple method of showing this relationship [that the magnetic field produced by an electric current is always oriented perpendicular to the direction of flow] is called the left-hand rule".

But in my physics text and my basic circuit theory text states it as the right-hand rule.

Which one is it?

Is is right-hand for conventional current flow and left-hand for electron flow?

2. ### Caveman Active Member

Apr 15, 2008
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Right. It explicitly states that the thumb is in the direction of electron flow. This means that it would be opposite for the direction of conventional current flow. While it is strictly correct, I disagree with ever using a left-hand concept with any of this. Everything else in classical physics uses right-hand rules. Let's keep it consistent.

3. ### Dave Retired Moderator

Nov 17, 2003
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This is a serious piece of misinformation in the e-book - yes it is the right-hand rule, or more accurately is represented in these terms by virtue of the solution to Biot-Savart Law on a current carrying conductor. The left-hand rule refers to trust on a current carrying conductor in the presence of a field.

Dave

4. ### Wendy Moderator

Mar 24, 2008
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That is the problem with 2 conventions, it is all too easy to get them mixed up from time to time.

5. ### Dcrunkilton E-book Co-ordinator

Jul 31, 2004
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Would it do any good to have two figures: one for conventional current flow emphasizing the right hand rule and another for electron flow refering to using the left hand without actualling calling it the left-hand rule?

6. ### thingmaker3 Retired Moderator

May 16, 2005
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Certainly, a diagram is worth a thousand words. The two examples side-by-side may well clear up the concept for many folk.

7. ### Dave Retired Moderator

Nov 17, 2003
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I am of the opinion that in the context of this article that only the right-hand rule (cupped-finger = magnetic-field, thumb = conventional current flow) is important - it is the most widely used context. Whilst I agree with thingmaker3 that a picture does paint a thousand words and that this may dispel some of the confusion on this, this episode has illustrated that the opposite may very well be true, that is that there is a risk of confusion when we introduce left and right-hand rules in the same discussion.

A further point I would make is that we have enough problems clearing up confusion about conventional Vs electron current flow, without adding left-hand-right-hand rules in there.

Just my 2 pence on this.

Dave

8. ### Wendy Moderator

Mar 24, 2008
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For what it's worth, my vote is to stick with electron flow, with a mention (no picture) that conventional flow uses the other rule. Two cents is worth even less than it used to be, but that's mine.

9. ### Dave Retired Moderator

Nov 17, 2003
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Yes, the cost of living of more than it used to be here too Bill!

Whilst I personally am more happy with electron flow (coming form a semiconductors background) I feel the conflict with using the left-hand rule in this case with electron current flow is that it goes against the convention on this in other standard texts on this subject (Seraway and Beicher spring to mind) who use the right-hand rule with conventional current flow. In essence the current diagram is correct for electron current flow, but this is not consistent with other texts that the reader may be accustomed to. The question is do we enforce one convention and stick to it rigidly, or do we aim to stick with convention for the clarity of the reader and pint out the differences/alternatives where appropriate?

Dave

10. ### Wendy Moderator

Mar 24, 2008
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The moment you start using both conventions side by side the confusion factor increases. In this text book it is said electron flow is the standard, I think we need to stick with it. As you did in your post it can be acknowledged that other systems are taught in passing (maybe mentioning other textbooks as you have done), so a discerning reader can understand why he has seen the other drawing from other sources.

Apr 20, 2004
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