Physics Half Yearly Questions (3 Viewers)

[coeyz]

Maybe it will... For example if you ever approach her in real life and she's near a door, then she might stick your fingers near the hinges of a door and break your them using the Torque provided by the door... In that case it would certainly help her


Yeah np, let us know how it goes. But I really do think your Physics teacher doesn't know what she's talking about, and that you should seriously do some self study if you want to do well in the course.

I cant get any extra marks :'(
she said i was playing with words and being ambiguous
she said when i was talking about torque. i should stick with the parallel idea :
(
hate her!!!!!

 

[cutemouse]

Re: I screwed up my half yearlies

I cant get any extra marks :'(
she said i was playing with words and being ambiguous
she said when i was talking about torque. i should stick with the parallel idea :
(
hate her!!!!!

What was your exact response? Could you type it up here?

If you stick with your teacher's way of explaining it, you MUST say that the AREA of the coil is parallel to the magnetic field, otherwise you wont get the marks in the HSC external examination.

Also, if the school endorses that you should get the SuccessOne books, then they should mark anything that you produce in an examination from the SuccessOne books as correct.

 

[gutzeit]

Re: I screwed up my half yearlies

I cant get any extra marks :'(
she said i was playing with words and being ambiguous
she said when i was talking about torque. i should stick with the parallel idea :
(
hate her!!!!!

:burn:That must be the head teacher?

Grrr I hate her!

Give me your exam next term and I'll take it to my dad He's a physicist ^^

Wo ai ni

 

[coeyz]

Re: I screwed up my half yearlies

:burn:That must be the head teacher?

Grrr I hate her!

Give me your exam next term and I'll take it to my dad He's a physicist ^^

Wo ai ni

OMG LOL! is this andy?

 

[coeyz]

Re: I screwed up my half yearlies

What was your exact response? Could you type it up here?

If you stick with your teacher's way of explaining it, you MUST say that the AREA of the coil is parallel to the magnetic field, otherwise you wont get the marks in the HSC external examination.

Also, if the school endorses that you should get the SuccessOne books, then they should mark anything that you produce in an examination from the SuccessOne books as correct.

**************
With reference to the physical principles involved, explain the operation of the galvanometer (3marks)

Faraday's Law states that when there is a change in flux, a voltage will be induced. (This bit is wrong i should say motor effect. My brain went wrong during exam but other things i wrote is fine) The galvanometer uses this effect to measure current. A coil is placed in a radial magnetic field produced by a pair of curved magnets. So the magnetic field is always perpendicular to the coi, ie. the torque will always be maximum. As the current is flow through the coil, it will experience a corce and the pointer attached will therefore turn and against the calibrated scale. The spring will produce an opposing torque to stop the pointer. The soft iron core is used to increase sensitivity.
This part is 3 marks and i got 0.

The next question :
The magnet is shaped so as to produce a uniform radial magnetic field. What is the advantage of having such a field? (1mark)

The field will always perpendicular to the coil, and therefore the torque will always be at maximum.
I got 0 mark here again.



Ye i have showed the success book answer to her.
wtf then she said : Im not responsible for that book. The answer there is wrong. I havnt explained the "area of the coil" thing to her yet coz she was away 1week before holiday :mad1:

Then i talked to my own physics teacher,
I did emphasise the word "AREA of the coil" and showed to formulas to him, then i said if i write "the coil is parallel to the field, so the torque is maximum" in the hsc i will get wrong.
Then he said, "well then make sure u say "area of the coil" to make it clear"
The teachers are just not willing to help you to gain any extra marks :mad1:

 

[sinophile]

Re: The "I didn't go well in my half yearlies" Thread

I dont see whats wrong, you should've got at least LEAST one mark for the first one. You just made the silly mistake of saying 'the coil' rather than 'the area of the coil'- the teacher should assume you mean the area of the coil anyway. But you didn't really explain the physical phenomena occuring in a galvanometer, so thats prob why you didt get full marks.

 

[cutemouse]

Re: I screwed up my half yearlies

**************
With reference to the physical principles involved, explain the operation of the galvanometer (3marks)

Faraday's Law states that when there is a change in flux, a voltage will be induced. (This bit is wrong i should say motor effect. My brain went wrong during exam but other things i wrote is fine) The galvanometer uses this effect to measure current. A coil is placed in a radial magnetic field produced by a pair of curved magnets. So the magnetic field is always perpendicular to the coi, ie. the torque will always be maximum. As the current is flow through the coil, it will experience a corce and the pointer attached will therefore turn and against the calibrated scale. The spring will produce an opposing torque to stop the pointer. The soft iron core is used to increase sensitivity.
This part is 3 marks and i got 0.

The first bit is correct too! There is a change in flux, so there is an induced EMF! That IS Faraday's Law.

The motor effect is where a current carrying conductor in a magnetic field experiences a force.

There is only one MINOR error in that answer and that is that you wrote "The galvanometer uses this effect to measure current" -- That is the motor effect that you are referring to, and instead, you should've written something like "The moving coil galvanometer depends on the motor effect". But it's very minor, and in the HSC you'll probably get the full 3 marks. At the VERY LEAST you should get 2 marks out of 3 for that question.

The next question :
The magnet is shaped so as to produce a uniform radial magnetic field. What is the advantage of having such a field? (1mark)

The field will always perpendicular to the coil, and therefore the torque will always be at maximum.
I got 0 mark here again.

That is PERFECTLY correct too!

I would DEFINITELY take this further, you should have gotten FULL marks for both these questions! I would definitely get the head teacher involved with the assistance of your parents. Not only are the answers perfectly correct, but if your school endorses/recommends that you should get the SuccessOne books and you reproduce their answers in an examination, then you they have to mark it correct.

I think your Physics teacher doesn't really know her stuff and is just teaching out of the book, ie. taking a 'memorised' approach to Physics when you should be UNDERSTANDING how these things works. Pity this is the case with many Physics teachers now days =(

Also, the two ways of describing the position of the coil (ie. in terms of area, or the actual coil itself) are exactly the same. It's like saying for example, the box is on top of the table, or the table is under the box. So they can't mark you wrong when you said the correct thing, but it didn't appeal to the teacher.

 

[gutzeit]

Re: I screwed up my half yearlies

OMG LOL! is this andy?

Yup ^^ Who else could it be

Our school is shit for physics None of the teachers understand what they're talking about.

 

[micuzzo]

Re: I screwed up my half yearlies

**************
With reference to the physical principles involved, explain the operation of the galvanometer (3marks)

Faraday's Law states that when there is a change in flux, a voltage will be induced. (This bit is wrong i should say motor effect. My brain went wrong during exam but other things i wrote is fine) The galvanometer uses this effect to measure current. A coil is placed in a radial magnetic field produced by a pair of curved magnets. So the magnetic field is always perpendicular to the coi, ie. the torque will always be maximum. As the current is flow through the coil, it will experience a corce and the pointer attached will therefore turn and against the calibrated scale. The spring will produce an opposing torque to stop the pointer. The soft iron core is used to increase sensitivity.
This part is 3 marks and i got 0.

The next question :
The magnet is shaped so as to produce a uniform radial magnetic field. What is the advantage of having such a field? (1mark)

The field will always perpendicular to the coil, and therefore the torque will always be at maximum.
I got 0 mark here again.



Ye i have showed the success book answer to her.
wtf then she said : Im not responsible for that book. The answer there is wrong. I havnt explained the "area of the coil" thing to her yet coz she was away 1week before holiday :mad1:

Then i talked to my own physics teacher,
I did emphasise the word "AREA of the coil" and showed to formulas to him, then i said if i write "the coil is parallel to the field, so the torque is maximum" in the hsc i will get wrong.
Then he said, "well then make sure u say "area of the coil" to make it clear"
The teachers are just not willing to help you to gain any extra marks :mad1:

ur teacher must be confusing herself with flux. ur answers are a bit clumsy(probably just exam nerve), however, they are still correct!

 

[pman]

Re: I screwed up my half yearlies

Yup ^^ Who else could it be

Our school is shit for physics None of the teachers understand what they're talking about.

Most physics teachers don''t understand what they are talking about and some parts of the course, no physics teachers understand, if they understood them they would be working at CERN and Fermilab (e.g. relativity)

 

[gutzeit]

Re: I screwed up my half yearlies

**************
With reference to the physical principles involved, explain the operation of the galvanometer (3marks)

Faraday's Law states that when there is a change in flux, a voltage will be induced. (This bit is wrong i should say motor effect. My brain went wrong during exam but other things i wrote is fine) The galvanometer uses this effect to measure current. A coil is placed in a radial magnetic field produced by a pair of curved magnets. So the magnetic field is always perpendicular to the coi, ie. the torque will always be maximum. As the current is flow through the coil, it will experience a corce and the pointer attached will therefore turn and against the calibrated scale. The spring will produce an opposing torque to stop the pointer. The soft iron core is used to increase sensitivity.
This part is 3 marks and i got 0.

The next question :
The magnet is shaped so as to produce a uniform radial magnetic field. What is the advantage of having such a field? (1mark)

The field will always perpendicular to the coil, and therefore the torque will always be at maximum.
I got 0 mark here again.



Ye i have showed the success book answer to her.
wtf then she said : Im not responsible for that book. The answer there is wrong. I havnt explained the "area of the coil" thing to her yet coz she was away 1week before holiday :mad1:

Then i talked to my own physics teacher,
I did emphasise the word "AREA of the coil" and showed to formulas to him, then i said if i write "the coil is parallel to the field, so the torque is maximum" in the hsc i will get wrong.
Then he said, "well then make sure u say "area of the coil" to make it clear"
The teachers are just not willing to help you to gain any extra marks :mad1:

Hey, here's the response from somebody who definitely knows what they're talking about - sorry

********
I agree with the school. The galvanometer has nothing to do with Faraday’s Law. It measures a dc current (i.e. a constant current) and there is no change in magnetic flux.

It is true that the galvanometer contains a coil placed in a radial magnetic field. The current flows through the coil. The magnetic field induced by the current is therefore along the axis of the coil. But the magnetic field is not perpendicular to the coil. The galvanometer works by magnetic attraction – the coil forms an electromagnet, and the curved magnet is the other magnet. The north pole of the curved magnet attracts the south pole of the electromagnet and vice versa. The sentence about the spring is correct. I don’t think a soft iron core is necessary, but it could be used to increase sensitivity.

So there are a couple of true statements in the answer, but it misses the point and I think zero is a fair mark.

For the second question, the field is not perpendicular to the coil. The field is radial so that it will always have the same effect no matter which way the coil is pointing (i.e., there will be a constant torque independent of the orientation of the coil). So again zero is a fair mark.

*******

Feel free to comment.

 

[cutemouse]

Re: I screwed up my half yearlies

I agree with the school. The galvanometer has nothing to do with Faraday’s Law. It measures a dc current (i.e. a constant current) and there is no change in magnetic flux.

Yeah but if you read the rest of her answer, you'll soon find out she just got the motor effect mixed up with Faraday's Law. That is pretty minor and should only cost 1 mark.

But the magnetic field is not perpendicular to the coil. The galvanometer works by magnetic attraction – the coil forms an electromagnet, and the curved magnet is the other magnet.

Excuse me?

The moving coil galvanometer depends on the motor effect which states that "a current carrying conductor in a magnetic field will experience a force" which is defined by F=BIlsinθ

For the second question, the field is not perpendicular to the coil. The field is radial so that it will always have the same effect no matter which way the coil is pointing (i.e., there will be a constant torque independent of the orientation of the coil).

Erm, the magnetic field is perpendicular to the coil, which ensures that the torque is always a maximum.

Another person who doesn't know his Physics... Geez I hope this one doesn't become a Physics teacher

 

[gutzeit]

Re: I screwed up my half yearlies

Yeah but if you read the rest of her answer, you'll soon find out she just got the motor effect mixed up with Faraday's Law. That is pretty minor and should only cost 1 mark.


Excuse me?

The moving coil galvanometer depends on the motor effect which states that "a current carrying conductor in a magnetic field will experience a force" which is defined by F=BIlsinθ


Erm, the magnetic field is perpendicular to the coil, which ensures that the torque is always a maximum.

I strongly suggest you reread what I posted - perhaps look here for further explanation - Galvanometer - MSN Encarta

Anybody else like to comment on the second question i.e. whether or not the magnetic field is perpendicular to the coil. I'm sticking with what I quoted about it being " radial so that it will always have the same effect no matter which way the coil is pointing (i.e., there will be a constant torque independent of the orientation of the coil)."

Another person who doesn't know his Physics... Geez I hope this one doesn't become a Physics teacher

I believe this person does know their physics. Sorry mate, he's a plasma physicist.

 

[cutemouse]

Re: The "I didn't go well in my half yearlies" Thread

Yeah except, the syllabus states:

"identify data sources, gather and process information to qualitatively describe the application of the motor effect in the galvanometer"

Actually, I don't know whether my Physics teacher has taught me correctly, after all he only has a degree in Electrical Engineering...

 

[gutzeit]

Re: The "I didn't go well in my half yearlies" Thread

Yeah except, the syllabus states:

"identify data sources, gather and process information to qualitatively describe the application of the motor effect in the galvanometer"

Yeh true about the syllabus... My excel book says under that syllabus heading "Electric meters, like motors, work on the motor principle by which a conductor carrying a current in a magnetic field experiences a force that is proportional to the size of the current in the conductor (for constant B and I)"

So nothing really about perpendicular and such!

Physics does my head in sometimes, everything is so specific!

Actually, I don't know whether my Physics teacher has taught me correctly, after all he only has a degree in Electrical Engineering...

I don't really know if many of us are taught correctly these days. A physics teacher who understands what they're talking about is very rare. My dad, who I quoted, was lucky to have the guy who writes all of these Excel Physics books as his year 12 teacher many years ago, so it shows what a good physics teacher can lead to!

A bad teacher on the other hand leads to confused students like me, you, and coeyz.

 

[cutemouse]

Re: The "I didn't go well in my half yearlies" Thread

Yeh true about the syllabus... My excel book says under that syllabus heading "Electric meters, like motors, work on the motor principle by which a conductor carrying a current in a magnetic field experiences a force that is proportional to the size of the current in the conductor (for constant B and I)"

So nothing really about perpendicular and such!

Physics does my head in sometimes, everything is so specific!

First, Excel hardly is a good textbook. It doesn't go into enough depth, this is a clear example of it being too summarised, and it is the reason why I don't use it.

Secondly, it's logic... if you have a radial magnetic field, then the coil will always experience maximum force, which only happens when the coil is perpendicular to the magnetic field.

A bad teacher on the other hand leads to confused students like me, you, and coeyz.

Excuse me? I never said I had a bad Physics teacher. Just so you know, my teacher has been teaching Physics since 1974, was a HSC marker who was promoted to a Senior Marker in his second year. He was even going to become a supervisor but he had to resign as he couldn't travel to Homebush (they moved marking centres).

If anything, he's one of the exemplar Physics teachers out there.

 

[gutzeit]

Re: The "I didn't go well in my half yearlies" Thread

Excuse me? I never said I had a bad Physics teacher. Just so you know, my teacher has been teaching Physics since 1974, was a HSC marker who was promoted to a Senior Marker in his second year. He was even going to become a supervisor but he had to resign as he couldn't travel to Homebush (they moved marking centres).

If anything, he's one of the exemplar Physics teachers out there.

Somebody needs to relax a bit...
I just took this:

Actually, I don't know whether my Physics teacher has taught me correctly, after all he only has a degree in Electrical Engineering...

as you saying your teacher isn't that good.
Don't have a rage because I didn't know all that good stuff about your teacher when I said most physics teachers are crap; I simply was considering the info you had provided previously. If you were attempting to be sarcastic, sorry I failed to pick up on it.

 

[gutzeit]

Re: The "I didn't go well in my half yearlies" Thread

First, Excel hardly is a good textbook. It doesn't go into enough depth, this is a clear example of it being too summarised, and it is the reason why I don't use it.

I merely provided part of what's under the syllabus heading. The rest was irrelevant to what we are discussing.

 

[cutemouse]

Re: The "I didn't go well in my half yearlies" Thread

Somebody needs to relax a bit...
I simply was considering the info you had provided previously. If you were attempting to be sarcastic, sorry I failed to pick up on it.

Yes I was being sarcastic... -_-;

The moving coil galvanometer happens to be studied in the field of electrical engineering, wouldn't you agree?

 

[gutzeit]

Re: The "I didn't go well in my half yearlies" Thread

Yes I was being sarcastic... -_-;

The moving coil galvanometer happens to be studied in the field of electrical engineering, wouldn't you agree?

Yes, I would agree, however that's no indication of whether he can teach it, hence why I didn't pick up on your sarcasm.