Oxford PAT 2016

Scroll to see replies

TangoTangoPapa2 posted this before and i was wondering if anyone had an easy to figure out that 1 and 6 were the solutions and not 4 and 3 or 5,2
Really been bugging my head for a while, without figuring out manually the values each combination wont give is there another way?

Question 11:
https://www2.physics.ox.ac.uk/sites/default/files/PAT-2011-Paper.pdf

Solution:
http://www.physicsandmathstutor.com/pat/solutions-2011/

Thanks in advance!

Reply 281

masterladfrank

Hey Guys

Applying from Australia here. i tried a few past PAT papers and found the maths section to be alright as our maths syllabus contains very similar questions. i am however having a lot of trouble with the physics section as alot of the content are not taught here in australia

do you guys have any recommendations to good resources/notes i can use to quickly learn all of the laws and formulae that would be in a-levels.

Reply 282

username2452153

Original post by masterladfrank

Hey Guys

Applying from Australia here. i tried a few past PAT papers and found the maths section to be alright as our maths syllabus contains very similar questions. i am however having a lot of trouble with the physics sectin as alot of the content are not taught here in australia

do you guys have any recommendations to good resources/notes i can use to quickly learn all of the laws and formulae that would be in a-levels.

Make sure you know the PAT syllabus, which is in their website.
I used http://www.physicsandmathstutor.com/physics-revision/ but the documents on the website are not available at the moment.

formulas can be found here : http://www.ocr.org.uk/images/77735-data-formulae-and-relationships-booklet-units-g481-to-g486.pdf You could google Physics formula booklet/datasheet for other version of the formulae sheets.

The problems in AS challenge and physics section of Oxford PAT are similar. You should attempt those as well. http://www.physics.ox.ac.uk/olympiad/PastPapers.html

!!! Good Luck !!!!!

Reply 283

rohan.nuck

Original post by NatoHeadshot

once you get C=-7 you can see that you require Ad1+Bd2 to be in the range 7-42. Note that you need every integer in that range, so if A>B, then d1=1 and d2=2 should give you 8. A+B=7 and A+2B=8 Which gives B=1 and A=6.

Reply 284

lawlieto

I have a few questions about electromagnetism.

Is there always a magnetic field around a current carrying wire? Even if the current is "steady"? I mean, dI/dt is a constant, not a function of t?
Why are electric fields due to magnetic fields concentric circles? (edit: I have seen the example of putting a copper ring in a uniform magnetic field, and when the flux linkage was increased that induced an emf and hence a current in the ring, and when there's a current, there's an electric field driving the charges, and that electric field would be concentric circles, but the electric field due to changing magnetic field exists without the copper ring as well, or without charges, which I can't understand atm)

Thanks

(edited 7 years ago)

Reply 285

username2452153

Original post by lawlieto

Yes, there is always a magnetic field around a current carrying wire. Yes even if the current is steady. In fact:
-Every current carrying conductor (Usually we deal with steady current) produces a magnetic field in every point in space around it.
Let us consider a small part of a current carrying conductor of length dl, then magnitude of magnetic field produced about this length at a point P around it is:
- directly proportional to the magnitude of the current
- inversely proportional to the square of the distance between the point and conductor.
- directly proportional to the sine of angle between the length of the conductor and the line joining conductor and point in space. :smile:

Reply 286

lawlieto

Original post by tangotangopapa2

Thank you

any ideas about the concentric circle electric fields? I really don't get why those electric field lines are concentric circles around a changing magnetic field and how they exist without charges.

Reply 287

username2452153

Original post by lawlieto

Why are electric fields due to magnetic fields concentric circles? (edit: I have seen the example of putting a copper ring in a uniform magnetic field, and when the flux linkage was increased that induced an emf and hence a current in the ring, and when there's a current, there's an electric field driving the charges, and that electric field would be concentric circles, but the electric field due to changing magnetic field exists without the copper ring as well, or without charges, which I can't understand atm)

Thanks

Let us think about the similarities between magnetic and electric fields. If you have a steady charge, then there is electric field around it. If you have a moving charge, i.e. current then you have magnetic field around it. They are in fact, different cases of the same phenomenon.

Hmm, I think there is a better explanation by Dr Kathy Romer. See the following thread, post no. 45.
http://www.thestudentroom.co.uk/showthread.php?t=4164901&page=3

Reply 288

username2452153

Original post by lawlieto

Thank you

any ideas about the concentric circle electric fields? I really don't get why those electric field lines are concentric circles around a changing magnetic field and how they exist without charges.

1) When there is change in magnetic flux current is induced in the copper ring. (Direction given by the Lenz's law)
2) Copper ring can be considered as a straight current carrying conductor bent into a circle. And this current induces magnetic field not electric field where field lines are tightly placed parallel circles with centre along the line of ring. There is also induced electric field due to changing magnetic field which is hard to analyse (needs knowledge of vector calculus).

I might be missing something.
Could you please link me to the question, if it is from one?

(edited 7 years ago)

Reply 289

lawlieto

Original post by tangotangopapa2

I am sorry but this question is not exactly getting into my head. Could you please link me to the question, if it is one?

Open this picture: http://www.linux-host.org/energy/ppimage67.gif
So there's a magnetic field into the page. The strength of this magnetic field is increased. This will create an electric field, in the form of a set of concentric circles.

(You can imagine that you put a copper ring in the magnetic field. When you increase the strength of the magnetic field, there will be a change in flux linkage through the copper ring which induces an emf, and hence a current in the copper ring. If there's current in the copper ring, an electric field is also present along the ring which drives the charges. However, there will be an electric field present when changing the magnetic field, even if there's no copper ring and the magnetic field is let's say, in vacuum)
So the thing I was wondering about is that, why is the direction of the electric fields is circular? Saying that "if there was a copper ring this and this would happen and then it would be circular" somehow doesn't sound like an explanation to me. :frown:

(read it in a book written by an authoritative physicist)
EDIT: if I think about it, the magnetic field produced by a current carrying wire is also a "circular" so it makes sense when people say "electricity and magnetism are different sides of the same coin" but there's still a big why :s-smilie:

(edited 7 years ago)

Reply 290

hellomynameisr

Hey guys,

I was doing the new specimen paper from the physmathtut website but I was confused on question 12.

I got the part on the left correct and was able to determine the resistance for each component but why does he use the formula 1/Rt = 1/R1... when calculating the resistance between A and B. I thought you could just add them all together and get 29/10 R? Are they still in parallel or something?

Can someone explain this to me please?

Link to solutions for the paper:
http://www.physicsandmathstutor.com/pat/solutions-2015-specimen/

EDIT: Sorry guys, I just realised my mistake... They are in parallel lol.

(edited 7 years ago)

Reply 291

username2452153

Try this question if you haven't already. Number c is really tricky. Took about an hour for me to realise. :biggrin:

Hint: It is not necessary to immediately dive into tons of equations from Kirchhoff's laws.

Reply 292

hellomynameisr

Original post by tangotangopapa2

Try this question if you haven't already. Number c is really tricky. Took about an hour for me to realise. :biggrin:

Hint: It is not necessary to immediately dive into tons of equations from Kirchhoff's laws.

I was able to get part A right but don't understand B and C :frown:

From the solutions, why does he do what he does in part B? I understand that p=v^2/r but how does he get the values to input them in from

And part C, how does he split up the circuit like that

Reply 293

username2452153

Original post by hellomynameisr

I was able to get part A right but don't understand B and C :frown:

From the solutions, why does he do what he does in part B? I understand that p=v^2/r but how does he get the values to input them in from

And part C, how does he split up the circuit like that

You need to know that voltage between resistors in parallel is same and equal to total voltage. Let's just look at the branch ADB. (R)AD = R/2 and (R)DB = R (fairly simple isn't it?).
Here comes the tricky bit. As resistance in BD is four times larger than resistance AD. Voltage dropped in BD is also 4 times larger than that dropped at AD.

Now it gets easy: The total voltage dropped is V and this is divided in the ratio 1:4. The voltage between BD is 4V/5 and resistance is R. Using the formula v^2/R you get the required answer.
:smile:

Part c is very tricky and so simple if you use simple trick. Are you sure you want to look at the solution below? :biggrin:

Think again!!! :P

Spoiler

Reply 294

NatoHeadshot

Original post by hellomynameisr

I was able to get part A right but don't understand B and C :frown:

From the solutions, why does he do what he does in part B? I understand that p=v^2/r but how does he get the values to input them in from

And part C, how does he split up the circuit like that

try redrawing the circuit and you should have solved it pretty easily :smile:

i hope this helped

Reply 295

hellomynameisr

Original post by tangotangopapa2

Part c is very tricky and so simple if you use simple trick. Are you sure you want to look at the solution below? :biggrin:

Think again!!! :P

Spoiler

Thank you for the explanation :biggrin:

Original post by NatoHeadshot

try redrawing the circuit and you should have solved it pretty easily :smile:

i hope this helped

What would it look like if I re-drew it? If you don't mind, could you send a diagram?

Reply 296

username2452153

Can't believe that summer is nearly over and I learnt almost nothing. Hard time ahead. :eek4:

But I have a plan. :idea:

(I always have plans. Only problem is that I never follow them. :tongue:

). I will start my preparation from today. :biggrin:

No, I am tired atm. I will start my preparation tomorrow. :smile:

. Surely, next week. :tongue:

How prepared is everyone by now?

Reply 297

hellomynameisr

Original post by tangotangopapa2

Can't believe that summer is nearly over and I learnt almost nothing. Hard time ahead. :eek4:

But I have a plan. :idea:

(I always have plans. Only problem is that I never follow them. :tongue:

). I will start my preparation from today. :biggrin:

No, I am tired atm. I will start my preparation tomorrow. :smile:

. Surely, next week. :tongue:

How prepared is everyone by now?

Not at all :rofl:

I proper feel like I am going to fail this exam and miss my Oxford place :cry:

Hopefully not tho lol

I feel okay for the maths section as I've completed the relevant A2 content but its the physics section that has me worried.

However, we all have until Nov 2nd which is plenty of time to get comfortable with everything and do all the past papers + more :biggrin:

Reply 298

Inert1a

For those who have 'Povey's perplexing problems'. Puzzle 1.5, I understand everything apart from the formula used for working out the area of the quadrilateral. Any help would be greatly appreciated.