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

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Reply 3820

Leeki

Can anyone please explain how a transformer works please?

Reply 3821

donutellme

Original post by MsFahima

oops. I understand what I've done wrong!

Oh sorry... :P it looked similar to another question asked earlier.... :biggrin:

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Reply 3822

MsFahima

Original post by donutellme

Oh sorry... :P it looked similar to another question asked earlier.... :biggrin:

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No no. I edited it. My mistake. :h:

Btw, that question.. what would the potential be? 50v?

Reply 3823

000alex

Original post by MsFahima

Potential is constant in a uniform field.

Why is it 25?

Reply 3824

a.a.k

Original post by EloiseFH

How are the graphs related for induced emf and flux linkage?

90 degree out if phase i think

Reply 3825

MsFahima

Original post by 000alex

Why is it 25?

I'm not sure.. :/

@donutellme help please?

Reply 3826

coqthepoliceman

could someone help me on the q17 and q12 on the jan 2013 paper

Reply 3827

donutellme

Original post by 000alex

Why is it 25?

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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Reply 3828

Ilovemaths96

right hand rule is for what again?

Reply 3829

dominicwild

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.

Reply 3830

000alex

Original post by donutellme

So it's always in that type of ratio?

Reply 3831

a.a.k

Original post by Ilovemaths96

right hand rule is for what again?

Moving wire

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Reply 3832

a.a.k

Original post by a.a.k

Moving wire

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Or any conductor

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Reply 3833

Substitution

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

Reply 3834

dannyoboy007

How do I solve these?

(edited 8 years ago)

Reply 3835

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)

Reply 3836

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

Anything to add/edit?

Reply 3837

MsFahima

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)