2002 paper. question 23 (b) (i) (1 Viewer)

[Squirrel]

Whats the answer?

I put Y.

am i right ?

 

[SmokedSalmon]

nope its X

use your left hand to find it.
Your four fingers in direction of magnetic field
thumb in direction of motion..
where is your palm facing? Towards X

 

[Squirrel]

Hmm.

left hand ey.

what if i use the right hand palm rule.
fingers point north to south (mag field).
palm points down because the rod will experience a force due to lenz's law
thumb points towards Y
And i cant remember whether induced current flows from neg to pos or pos to neg.

or maybe i have it all wrong.

 

[helper]

Squirrel, your explanation is right but answer is wrong.

The positives are pushed towards end Y making it positive.

If there was an external circuit connected, the current would flow to from Y to X in the external circuit. From positive to negative.

 

[-X-]

SO the answer is Y?

 

[helper]

No the answer is X. The positives are pushed to the Y end (figuratively, as only the negatives move). The electrons are pushed to the X end.

Y is therefore Positive and X is negative.

Salmon's explanation is also correct. By using the left hand you are looking at the movement of electrons.

 

[failingTheHsc]

if positive charges are pushed to one side. than that is the conventional current. convential current states that current goes from positive to negative.

applying the right hand rule positive charges in the rod will head towards Y

so why isnt Y negative???????

positive charges are attracted to negative. it doesnt make sense

 

[helper]

Failing.

This is an induced EMF not an external current.

The movement produces an EMF, like a battery is an EMF. The EMF then drives a current in an external circuit, if connected.

So if X and Y were connected by a wire. The conventional current would flow from Y to X in the external circuit.

Thus Y is positive and X is negative for the EMF

Think of the induced EMF as a water pump up a cliff. It increase raises the water to the top of the cliff. Once the water is there it will flow down the cliff.

The Induced EMF is the water pump. It moves the positives to +, and negatives to the negative. The ppositives then flow back to the negative in the external circuit.

 

[-X-]

Originally posted by helper
No the answer is X. The positives are pushed to the Y end (figuratively, as only the negatives move). The electrons are pushed to the X end.

Y is therefore Positive and X is negative.

Salmon's explanation is also correct. By using the left hand you are looking at the movement of electrons.

Ahh sorry. I thought it sayed which is positive.

failingTheHsc: All i know is that induced current in a generator always flows towards the positive (making y positive).