Can Fleming's left hand rule be used for induced currents?

[thebosonbreaker]

Hello all,
I understand the distinction between FLHR and FRHR. The LHR is used primarily for motors, while the RHR is used for generators/induced currents.

For a conductor moving between magnetic poles, we can use the RHR to predict the direction of the induced current. According to the diagram below (the conductor is moving downwards), using the RHR tells us that the induced current will be out of the plane of the screen.

As I understand it, the rules (left hand and right hand) are referring to conventional current (please correct me if I'm wrong). So that means that in the example shown in the diagram, the direction of electron motion is actually into the screen.

If we could magnify the view of the conductor, we would see electrons. These electrons are in a magnetic field and therefore (a moving charge in a magnetic field) experience a force. Is it possible to use the left hand rule to predict the direction of the induced current (which should be opposite that of the motion of the electrons if both rules refer to conventional current) based on this idea?

If so, could someone please explain how.

Thank you in advance.

 

[sophiecentaur]

Why bring electrons into this? All this stuff was sorted out, way before the electron was discovered so don't call it 'conventional current'; just call it 'current' and don't add to the aggravation about EM - it's hard enough as it is.
PS you got the direction of the current right so leave it at that.

 

[rude man]

FYI the right-hand rule is just a convention. When I was in high school (~1955!) our textbook, Physics - A Basic Science used the left-hand rule! Worked just as well. But to effect commonality we all have since agreed on the right-hand rule.

 

[sophiecentaur]

FYI the right-hand rule is just a convention. When I was in high school (~1955!) our textbook, Physics - A Basic Science used the left-hand rule! Worked just as well. But to effect commonality we all have since agreed on the right-hand rule.

I can't think how you applied a RH rule when the LH rule applies - or vice versa if you use the standard directions for current, emf, field vector and motion or force. Which non-standard convention were you using for this rule?
The hand of the rule depends upon whether it's the Generator Rule (RH) or the Motor Rule (LH) that you are using.
PS 1955 is very recent in the context of all this basic EM stuff; nothing has changed for over a hundred years. (I reckon my exposure to Flemming must have been about 1956/7 and there's never been any disagreements in any of my textbooks.

 

[rude man]

I can't think how you applied a RH rule when the LH rule applies - or vice versa if you use the standard directions for current, emf, field vector and motion or force. Which non-standard convention were you using for this rule?
The hand of the rule depends upon whether it's the Generator Rule (RH) or the Motor Rule (LH) that you are using.
PS 1955 is very recent in the context of all this basic EM stuff; nothing has changed for over a hundred years. (I reckon my exposure to Flemming must have been about 1956/7 and there's never been any disagreements in any of my textbooks.

I did not say ",,, applied a RH rule when the LH rule applies ... ". I effectively said the left-hand rule when used consistently is every bit as good as the r/h rule.

If you "can't think" how that works then maybe you'll get a copy of it & see: https://www.amazon.com/dp/B00846T54E/?tag=pfamazon01-20.

There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy. ... Hamlet

 

[sophiecentaur]

I effectively said the left-hand rule when used consistently is every bit as good as the r/h rule.

I see what you are saying but the book is not consistent with (all the) others. That seems crazy - whatever the claimed justification (below). Fleming should be left well alone until the Lorentz Force comes along. (Only a small number of students at a higher level)
The problem with all this is that the Lorentz force (Cross product)on a moving positive charge in a Field is part of a right hand vector set. That's where the confusion really comes in but students can cope with this in the same way that they cope with electron drift direction and conventional current. It's too late to change and I really don't think your book is being helpful. (Quite upsetting really. )
We were taught the GeneRIGHTer rule and that Motors drive on the Left (at home in UK) so that makes life easy for School students here.
PS That was a nice PF detour.

 

[rude man]

I see what you are saying but the book is not consistent with (all the) others. That seems crazy - whatever the claimed justification (below). Fleming should be left well alone until the Lorentz Force comes along. (Only a small number of students at a higher level)
The problem with all this is that the Lorentz force (Cross product)on a moving positive charge in a Field is part of a right hand vector set. That's where the confusion really comes in but students can cope with this in the same way that they cope with electron drift direction and conventional current. It's too late to change and I really don't think your book is being helpful. (Quite upsetting really. )
We were taught the GeneRIGHTer rule and that Motors drive on the Left (at home in UK) so that makes life easy for School students here.
PS That was a nice PF detour.

Right you are. And my apologies for being a bit brusque.

I certainly would not want to encourage anyone to use the left-hand rule, even consistently. I thought it might be helpful to the OP to understand that the r/h rule is not sacred per se but a convention that everyone has adopted long ago. The text I referred to is from 1943 (but used in my 1955 h.s. class) and hopefully it's the last.

And BTW I believe the term "conventional current" is still encountered now and then, albeit mostly in introductory texts. I think I even ran across it relatively recently myself.

 

[sophiecentaur]

And my apologies for being a bit brusque.

Brusque? Positively kid gloves, I would say.
When I was doing it all, first time round, we were just not allowed to discuss electrons in our circuit theory. I don't think it ever harmed my learning. What it did do was to let me believe that what works, works and, once you've learned something, you can see it in the wider context of a working model. "What's REALLY happening?" Bahhh.

 

[rude man]

Long live "what works, works"!

Modern physics has in fact obscured the term "electron" anyway. But in classical physics it still exists as a particle & is the carrier of electricity. But I think you're right - it should not be invoked as the current carrier after high school.

I don't have that text I mentioned & I'm wondering if they used the l/h rule in conjunction with electrons as current. Physics in high school, at least in the U.S., is such that when we get to (what we call) college the 1st thing we are told is that everything we learned in high school is wrong anyway, with which I basically concur. I have jousted with some anent this but they were usually high school teachers. Some of them even contend high school history is accurate LOL!