Q19 2012 HSC Physics (1 Viewer)

[skillstriker]

I got D but the answer is C. I thought that the resistance to the eddy currents generates heat. Can someone please explain?

 

[RealiseNothing]

Consider

We want to make as large as possible since it it the Eddy Currents (I) that produce the heat. If the resistance is high, then the current will be low. So the resistance must be low for the current to be high.

 

[someth1ng]

If you think about it, if the resistance is higher, there are less currents (that's why we increase resistance in transformer cores).

I believe this is a legitimate way of explaining it:
Ohm's Law: R=V/I

P(loss)=I^2 R
P(loss)=(V/R)^2 R
P(loss)=V^2/R

As you can see, a higher voltage will cause a higher P(loss), a lower resistance will cause a higher P(loss).

 

[anurag96]

Hey, yeh i got D for 19 aswell cos if you think about it logically for say in a lightbulb filament wire, the wire has a very high resistance which produces the heat quickly as opposed to having a high current running through the wire... i even asked my and school teacher and then tutor and they said something along those lines aswell....

 

[iBibah]

Hey, yeh i got D for 19 aswell cos if you think about it logically for say in a lightbulb filament wire, the wire has a very high resistance which produces the heat quickly as opposed to having a high current running through the wire... i even asked my and school teacher and then tutor and they said something along those lines aswell....

Unfortunately they are both wrong, refer to the two above posts.