Quick Question on Lenzs Law (1 Viewer)

[KFunk]

No, it won't. The electron current will flow from B to A, but that definition of current is inexpedient to this situation. We are dealing with conventional current in this instance, which will flow from A to B (Conventional current is defined as a flow of positive charge). Besides, finding the direction of current flow after induction wasn't even the question.

In this instance I think conentional current goes B to A. Remember the relationships for induced current are slightly different to those involved in the forces on a conductor in a magnetic field. The various palm rules deal with conventional current. So in this case the electrons are flowing from A to B.

See my other post. Also, note that they don't actually move (Judging by your evident, and seemingly lingering, shakiness with this concept, this reinforcement should serve you well). Even if current (conventional, remember) did end up flowing from B to A, which it doesn't, this would make B positive and A negative (why would it leave something it's attracted to?)

This bugs me too and I'm still unsure of it. I think the reasoning is that they are moving due to the magnetic force acting on them. This causes the electrons to move from A to B causing a defficieny of negative charge at A and a surplus at B.

The word is when, and not wen, by the way, idiot. If I were you, I'd be steering your argument away from conventional current, dude, since your mixing up of ideas thereof has led to its being corrected in the first place.

We deal with conventional current because the rules we are taught deal with conventional current not electron flow. When we use current in our formulae like F = BIsinθ we are working with conventional current. (btw, be nice and don't call people 'hacks'/'idiots')

It's reassuring to see that you know something, even if it happens to be the most obvious point to have ever shown its face in the syllabus; now, all you need to do is apply it correctly! But, don't rush yourself... take little, baby steps and you'll get there eventually

Partonising much? Don't worry, I luv ya will, *blows kiss* !!

Positive charge doesn't move. B isn't losing positive charge, as you are implying. This cannot happen, and has nothing to with the definition of conventional current (which is a wholly academic concept, by the way), nor with electromagnetic induction.

A man can make a hypothetical... He was illustrating a point dude.

Uhhh... is this supposed to impress me? I can tell just by receiving your messages that you're not at all hot, man. Why should I care about a mark, which, incidentally, isn't that good, and whose calculation, for all I know, was subjected to all forms of bias, partiality, luck and misalignment, when I can evaluate your calibre right here and now? You ain't got nothing, man, and certainly can't dance with the big guns. I've seen some of your other posts.

I agree with you that it shouldn't be used to justify how correct he is. It's not a PhD. However, it indicates that he's not an idiot and that you shouldn't be as rude as you were when you patronised him.

 

[Will Hunting]

In this instance I think conentional current goes B to A. Remember the relationships for induced current are slightly different to those involved in the forces on a conductor in a magnetic field. The various palm rules deal with conventional current. So in this case the electrons are flowing from A to B

No, you are speaking of conditions before induction. I am speaking of them after. You have misunderstood my post, and misrepresented your stance. What you've said is not incorrect, but nor is mine incorrect (what do you think of my double negative usage there?). Oh, and drop the didactics. There's nothing you can teach me that I don't already know. Trust me. You might get lucky with a correction someday, but, no, never shall you teach.

This bugs me too and I'm still unsure of it. I think the reasoning is that they are moving due to the magnetic force acting on them. This causes the electrons to move from A to B causing a defficieny of negative charge at A and a surplus at B.

a) I understand it. So don't bother with an explanation I am already aware of and have already given, to others, myself.

b) It shouldn't bug you. I've already explained it for you. If you have any further probs with it, don't hesitate to ask me for a hand. I'd be happy to lend it

We deal with conventional current because the rules we are taught deal with conventional current not electron flow. When we use current in our formulae like F = BIsinθ we are working with conventional current. (btw, be nice and don't call people 'hacks'/'idiots')

A useless inclusion to the thread. Not only am I completely up to speed with this concept, but I have actually, as recently as in my last post, and earlier in another thread (I can't find it right now, but I'll shoot it through to you if I do) given a comprehensive explanation of it, more than demonstrating my knowledge of the concept, and more than proving your post, here, unnecessary and actually dectracting from the stoicism of your argument.

A man can make a hypothetical... He was illustrating a point dude.

No, he wasn't. Nor are you. And, no, a man can't make a hypothetical like this, if he doesn't wan't to be left open to criticism from those more perceptive.

I agree with you that it shouldn't be used to justify how correct he is. It's not a PhD. However, it indicates that he's not an idiot and that you shouldn't be as rude as you were when you patronised him

Thanks for your input, however, you are in no position to interlope in my affairs, nor pass judgment on appropriate social customs and propriety. It indicates, to you, perhaps, that he is not so, but, to me, my initial statement holds. He is such compared to me, so I can make a statement like that with impunity. It's quite simple, really.

 

[KFunk]

No, you are speaking of conditions before induction. I am speaking of them after. You have misunderstood my post, and misrepresented your stance. What you've said is not incorrect, but nor is mine incorrect (what do you think of my double negative usage there?). Oh, and drop the didactics. There's nothing you can teach me that I don't already know. Trust me. You might get lucky with a correction someday, but, no, never shall you teach.
.

I don't understand why you would talk about the conditions after?? As you rightly pointed out, the question deals with charge during motion and not after.

I may have missed it but I didn't see anyone, other that you, discuss the situation after motion. In any case the charge after motion will just balance itself out and you shouldn't have a charged end.

You are wrong. By your logic, A will become negative, which is, incidentally, what I have already explained three times now. Try throwing off the shackles of an indefensible narcissism and listening to others for a change. You might save yourself some embarrassment. Conventional current is defined as a flow of positive charge (your word usage in positives, by the way... dude.. no). If B becomes negative, as you have said, that means electrons will move from B to A (since electrons migrate to the positive pole) i.e. current will flow from A to B. But this will cause a force acting up the page. How can applying an intial force up the page induce a current to produce a second force that also acts up the page, not opposing, but rather adding to the intial force (and therefore energy)? Your proposition defies the law of conservation of energy. You are wrong.

This is what I'm arguing against. I don't think you're justified in accusing him of being wrong. You say "by your logic" but you really aren't stepping into his shoes and thinking the way he is. Try his logic out.

 

[KFunk]

Oh, and drop the didactics. There's nothing you can teach me that I don't already know. Trust me. You might get lucky with a correction someday, but, no, never shall you teach.

This is the one statement you have made where I can safely say that you are 100% incorrect . Unless you are an infallible divine being there is a lot you could learn from me.

 

[rama_v]

omg, so what the hell is the answer here

I second that.

 

[velox]

whoa dickheads calm the fuck down. Keep ur feet on the ground!

 

[frenzal_dude]

K i am coming last in my class in physics,
and even 2 me this question seems so easy,
don't you just use the right hand plam rule?

movement of positive charge is upwards, field lines are into the page, therefore the positive charges are forced to the left which is going 2wards A,

if positives charges are forced 2wards A, doesnt that mean A is the negative end, becuase opposites attract????

---
crap wait a minute, the positive charges would gather at the A end, meaning that the A end would be positive, and B is negative coz the positive charges leave the B end? farout i dunno.......

 

[thunderdax]

You guys should look in any textbook about questions like this involving rods, not circuits. Since the positive charges flow to A (or the negative charges flow to B), end B will become negative.

 

[rama_v]

You guys should look in any textbook about questions like this involving rods, not circuits. Since the positive charges flow to A (or the negative charges flow to B), end B will become negative.

lol this is an olld thread, I know the answer now so dont fret thanks anyway,

 

[rnitya_25]

lol point noted.....

 

[frenzal_dude]

k i finally worked this out, i don't think any1 has thought of this yet, what you do is add an external circuit onto it.

So if I flows from B to A thru the rod, which is like the battery cell/electron pump thing, then I acutally flows from A to B in the external wire/circuit which is what we need 2 be loooking at.

A to B, conventional current I is positive to negative, which means B has to be the negative end.

 

[james_chappo]

k i finally worked this out, i don't think any1 has thought of this yet, what you do is add an external circuit onto it.

So if I flows from B to A thru the rod, which is like the battery cell/electron pump thing, then I acutally flows from A to B in the external wire/circuit which is what we need 2 be loooking at.

A to B, conventional current I is positive to negative, which means B has to be the negative end.

HOW EROTIC....

 

[james_chappo]

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[FinalFantasy]

LoL!!
dat is funny, where u suddenly pop up in da physics forum with dat!??

 

[Abtari]

Question Incomplete!

the question is not complete:

The rod AB is moving upwards through the magnetic field B going into the page as shown. Which end of the rod is negative?
--------------------------------------------------------------------------------------------------------
is the rod moving because we moved it (i.e. just like we move the conductor in a generator) or is it moving because of the motor effect (i.e. just like a conductor moves in a motor).

if WE moved the rod, then current is induced. i.e. we would have to use the LEFT HAND RULE. from this we get INDUCED current flowing from B ---------> A.
so from this perspective, negative end: A

if the rod is moving as it is because of the motor effect, then the current is NOT induced. i.e. we would have to use the RIGHT HAND RULE. from this we get current flowing from A---------> B.
so from this perspective, negative end: B

 

[speed2]

abtari stop over complicating the question!!

 

[Abtari]

what do u mean overcomplicating... i was just saying that the question didn't specify whether the current was induced like in a generator or whether it was provided by a supply emf like in a motor.... read the question for urself.

you can have totally opposite answers depending on which scenario you take. that is why i think we are all getting caught up between "A" and "no its B" and so forth. this is because for one scenario you have to use the right hand rule (motor scenario) whereas for another you have to use the left hand rule (generator scenario).

if in doubt, ^^^^^^^^^ please refer to the above post.

 

[rnitya_25]

oh good lord. this thread is wel over a month old, get over it. the questions been answered. lol.....put up more questions...forget this.

 

[Abtari]

oh good lord. this thread is wel over a month old, get over it. the questions been answered. lol.....put up more questions...forget this.

well according to what speed2 just said, it seems quite pertinent.

what is the correct answer anyway for this question?

 

[rnitya_25]

the answer is B.