Worried about some motors and generators stuff (1 Viewer)

[Mathsisfun15]

Due to contradictions in information from both HSC and textbooks I just want to clear a few things up.
For the purpose of the HSC are eddy currents formed with a copper tube with a slit in it? (there was a HSC MC that said they didn't yet there was a HSC long response that said they did. I know IRL they do as I've seen it myself)

 

[Mathsisfun15]

Also with induction cooktops is it fine to say that AC causing alternating magnetic field that causing eddy currents to be induced by Lenz's Law (obviously i'd elaborate in test) in the pan and due to the high resistance of the pan since P=I^2 *R heat is produced to cook the food. Because irl Iron are used not lower resistance metals such as copper I know this is due to their ferromagnetic properties.
I know this thread (http://community.boredofstudies.org/18/physics/328351/eddy-currents-induction-cooktop.html) says that lower resistance is better based seeing as eddy currents are larger but without resistance no heat would be produced so surely both are significant though

 

[mrpotatoed]

I know what Q you are referring to and in reality very small eddy currents form and it would have an effect on the speed, but im guessing its negligible. And the guys at BOS running the phy course being as shit as they are doesn't acknowledge the fact that small eddy currents form in the tube with slits

and with the induction cooktops, Since V=IR, I=V/R
the 'voltage induced' is constant as the rate of flux from the AC doesn't change based on the different metals of the saucepan. A low resistance pan creates big currents, big currents dissipate as heat, that as my understanding.

 

[InteGrand]

For the purpose of the HSC are eddy currents formed with a copper tube with a slit in it?

For the purposes of HSC Physics, no.

In reality, yes.

So if asked in the HSC, you should probably say no.

 

[Magnoliatient]

For induction cooktop high resistance is better. It is not electric current, but heat that cooks food. The heat in the pan is caused by resistive heating (When electrons collide with the positive metal lattice, they transform kinetic/electric energy into heat energy). Hence, it needs high resistance, not high current. (so saying that high current dissipates heat is not technically correct in this case)

 

[Mathsisfun15]

For induction cooktop high resistance is better. It is not electric current, but heat that cooks food. The heat in the pan is caused by resistive heating (When electrons collide with the positive metal lattice, they transform kinetic energy into heat energy). Hence, it needs high resistance, not high current

Some sources say that and that is what I thought but sources such as the link I posted in my 2nd post violate that.
What would the markers opinion be?

 

[Mathsisfun15]

For the purposes of HSC Physics, no.

In reality, yes.

So if asked in the HSC, you should probably say no.

the marking guidelines for q25 says eddy currents are induced but no breaking (http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2011exams/pdf_doc/physics-marking-guide-11.pdf) so basically according to the HSC it seems that they do form but they are insignificant in size so no breaking

 

[HecticLad]

the marking guidelines for q25 says eddy currents are induced but no breaking (http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2011exams/pdf_doc/physics-marking-guide-11.pdf) so basically according to the HSC it seems that they do form but they are insignificant in size so no breaking

It will usually form smaller eddy currents in each metal slit, there will still be braking but it will be much smaller

 

[InteGrand]

the marking guidelines for q25 says eddy currents are induced but no breaking (http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2011exams/pdf_doc/physics-marking-guide-11.pdf) so basically according to the HSC it seems that they do form but they are insignificant in size so no breaking

There was also an infamous MCQ in a past HSC involving dropping a magnet down three tubes, and you had to assume no Eddy currents formed in the one with the slits to get the Board's answer. If you assumed what happens in reality (that small Eddy currents are formed), you would get an answer that would be incorrect according to the Board of Studies, and so you'd get 0 for that MCQ.

I can't remember which year it was, but maybe you know which Q I'm talking about.

 

[Fizzy_Cyst]

Due to contradictions in information from both HSC and textbooks I just want to clear a few things up.
For the purpose of the HSC are eddy currents formed with a copper tube with a slit in it? (there was a HSC MC that said they didn't yet there was a HSC long response that said they did. I know IRL they do as I've seen it myself)

If there is no closed loop = no eddy current

There will still be an EMF, just no eddy current, hence no braking force.

#hscsez

 

[Mathsisfun15]

There was also an infamous MCQ in a past HSC involving dropping a magnet down three tubes, and you had to assume no Eddy currents formed in the one with the slits to get the Board's answer. If you assumed what happens in reality (that small Eddy currents are formed), you would get an answer that would be incorrect according to the Board of Studies, and so you'd get 0 for that MCQ.

I can't remember which year it was, but maybe you know which Q I'm talking about.

yeah I know the one you are talking about and that sparked my doubts with what to do for hsc