question, please answer got half yearlies tommorow (1 Viewer)

[Li0n]

http://www.members.optusnet.com.au/komainu/help.JPG

according to the answers they say
"A, Using the right hand push rule on the left hand part of th eloop. Fingers to the right, thumb into the page gives the palm facing down. The current will flow down to the left hand carbon brush and then to the right through R. THe commutator has a split ring so the current will always go the same way, i.e. to the right"

Ok firstly, its the left hand rule for generators correct me if im wrong, and secondly i say its b. because using the left hand on the right part of the loop points the current down, which means the current must be coming up from the other side...

 

[xiao1985]

uhm.... ambiguity, conventional currently or electrical current???

electrical current: to wards (edit: left)
conventional current: the other way... ie , (edit right)...

(edit: sorry the answer is right... conventional current goes to the right)

 

[Li0n]

ahh thanks, i remember we had this argument in class (question was from NEAP), (so was the answer), but i ah.... forgot :|

 

[wogboy]

For that generator the answer is A. I prefer to think of it in terms of Lenz's law and the right hand grip rule. The source magnetic field is going right. So the induced magnetic field (from the rotating coil) must be going to the left. Using the right hand grip rule (where you curl your fingers in the direction of the current) you'll find that the answer is A. The current in the resistor flows from left to right.

Alternatively, if you wish to use the left hand rule (I personally don't like it), your thumb points in the direction of the force exterted by you on the coil, your "ring" finger pointing in the direction of the magnetic field, so then your "pointing" finger will point in the direction of the current, which yields the same result as the right hand grip rule.

 

[xiao1985]

again... the question is ambigious as it does not state whether it is conventional or electircal current

 

[George W. Bush]

It's obviously assumed to be conventional.


That's why it's the convention.

Note I haven't read the question and might be making an ass out of myself.

 

[wogboy]

again... the question is ambigious as it does not state whether it is conventional or electircal current

Acutally conventional current is the same thing as electrical current, they are both in the direction of POSITIVE charge flow (this is what is commonly used). What you're getting confused with is electron flow, which is in the direction of NEGATIVE charge flow (this is hardly ever used).

NB: In a metal wire there are no positive charges flowing, only electrons flowing, so conventional/electrical current is taken to be in the direction opposite to which the electrons flow in the metal wire.

 

[xiao1985]

no... electrical current is the current which electrons flow.. towards the positive direction...

the direction would be opposite of that of conventional current...

if it is talking abt conventional current, then the current should be from right to left... ie b... because:

there is a relative motion between the coil and the B ... therefore, back emf will be induced to interact with B in such a way that it produces a force opposing the relative motion... that is, producing bak emf that interact with external B to produce a force anticlose wise on the coil....

*thinks

sorry, my sincerest apologies, my answer above is wrong... the conventional current goes from left to right... i used the right hand rule and mistakenly thought the current is electrical current

i will edit my post above to correct it... and yes, conventional current flwo from left to right...

 

[t-i-m-m-y]

in physics we almost alwasy use conventional current when describe circuits

 

[Zarathustra]

I heard that in the catholic trial that current is taken to be "electron flow" but in almost all other cases its conventional.