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# AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread] watch

1. right hand rule is for what again?
2. (Original post by Dante991)
Very good question. If it says something like 'radius is doubled' etc, then formulate an equation and sub in 2r or 2m etc, and then you will find the overall equation is being multiplied by a single constant. so if F= 2m / (2r)sq, then F is being multiplied by x 2/2sq = 2/4 / 1/2 so the new force will be 1/2F. Hope this helps but these questions are the toughest
Yeah, for me it turns into an algebra treasure hunt. To luckily find the right formulas or see some way to re-arrange something into some form of an answer the question wants.

Sometimes you can miss parts out in understanding though in some algebra questions. Like once I forgot to include some part in my substitution, so a picked the one which closely resembled mine and it was right.
3. (Original post by donutellme)
Sorry, I thought it was a different question.

Field strength is the gradient of the potential. So in a uniform field, in this case 50, the potential goes from 50 to 0. That means half way along it's gonna be 25.

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So it's always in that type of ratio?
4. (Original post by Ilovemaths96)
right hand rule is for what again?
Moving wire

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5. (Original post by a.a.k)
Moving wire

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Or any conductor

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6. (Original post by Ilovemaths96)
right hand rule is for what again?
stick your boy the thumb out and wrap them fingers around and your thumb points in current direction with fingers showing which way the magnetic field will rock up
7. How do I solve these?

8. Can anyone help with this question? Im sure its quite simple and i might be missing something but when i use F=mw^2r, im getting 19N..

The answer is apparently D, 24N.

(this is from june 13)
9. how transformers work:
When alternating pd is applied to primary coil, alternating magnetic field is produced in core.
Field passes through secondary
From faraday's law and alternating magnetic flux induces emf in secondary coil

10. (Original post by darkni35)

Can anyone help with this question? Im sure its quite simple and i might be missing something but when i use F=mw^2r, im getting 19N..

The answer is apparently D, 24N.

(this is from june 13)
It's basically. Total force = Tension - mg.

So

T - mg = mw^2r

Now try.

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11. (Original post by Ilovemaths96)
right hand rule is for what again?
For induced current/emf
12. Good Luck and Good Night guys!

Hope you all do well.

13. Good luckerino to everyone!
14. Good luck everyone

Wish you all the best
15. Don't stress about the exam, I'm in a worse situation than you. Ive just finished the june 14 paper, so yeah, but I'm totally relaxed as i have been with my other exams because least i know I've tried my best as you have.

Don't worry if a question doesn't make sense or wordy, think about it slowly even if you end up working on it for more than expected. Remember, it's not 1.45 mins per mark. If you end up thinking about a question for more than 2 minutes and you still haven't found the answer and that you think you are not close to the answer then you should leave it and carry one with the rest.

Remember you must tick the answer of MC section on the answer sheet so don't try to choose the answers on the question paper and then transfer them to the answer sheet at the end as this would waste your time. Each time you solve a question just quickly tick the answer on the answer sheet, forget the question paper.

If you are starting with multiple choice then once 45 mins is over start the written one as it's has an easier flow. If you are starting with written part and not concerned much about the MC then finish the written part first then spend the remaining time on MC.

I really hope you will all achieve the best you can.
Good luck everyone

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16. (Original post by dannyoboy007)
How do I solve these?

work out potential of all charges at point P and then just add all the potentials together since its a scalar
17. (Original post by Ilovemaths96)
how transformers work:
When alternating pd is applied to primary coil, alternating magnetic field is produced in core.
Field passes through secondary
From faraday's law and alternating magnetic flux induces emf in secondary coil

That's it really

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18. (Original post by dannyoboy007)
How do I solve these?

First one.. i think you take the charges in isolation. Use V=1/4piEo*Q/R
I got 180V for each charge *2 = total of 360V since potentials are a scalar quantity.

Second one.. same thing, but distance between each charge and P is root 2*a using trig.
Hence, the total potential is 4*(1/4piEo*Q/Root 2*a) which simplifies to Q/PiEo root 2 a.. so it should be b.

Not 100% if these are right though
19. (Original post by Mehrdad jafari)
That's it really

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Awesome good luck mate
20. GOOD LUCK BOYS AND GIRLS! Remember a geosynchronised satellite orbit is one that orbits its planet in the same time period as it takes the planet to rotate (would be 24h time period orbit for one around earth). I only learnt this today as it got me stuck on a past question, it's just there in case anyone needs it! Adios.

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