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The direction of the force does depend on the sign (positive or negative) of the charge but it does not depend on the size of the charge. However the magnitude of the force does depend on the size of the charge (size as in +1 or +5) :smile:

Ah thanks for clearing that up. So that means Fleming's left hand rule to ind the direction of force only works for electrons - a positron means you should use Fleming's right hand rule.

Also yeah I had meant to say size of the force when referring to magnitude of charge, whoops.

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Reply 61

NDVA

Original post by Rhetorical Hips

I always pretend the charge is positive and use Fleming's left hand rule to work out the direction of the force. Then if the charge is in fact negative I just switch it to the opposite direction :smile:

Reply 62

Rhetorical Hips

Original post by NDVA

I thought that the force on an electron was given by Fleming's left-hand rule

Reply 63

NDVA

Original post by Rhetorical Hips

I thought that the force on an electron was given by Fleming's left-hand rule

The middle finger represents the direction of the conventional current (i.e positive charge). I think my variant is different from yours? :tongue:

Reply 64

Rhetorical Hips

Original post by NDVA

The middle finger represents the direction of the conventional current (i.e positive charge). I think my variant is different from yours? :tongue:

Yeah looking online it seems that Fleming's left-hand rule means different things to different people!

EDIT: That said, I've figured it out now and I agree with what you said :smile:

Confusion is due to the fact that 'conventional current' is regarded as the flow of positive charge. I assumed that the force on the wire would be the same direction as the force on an electron (which it surely is in reality, they're both involving the movement of negative charge?), but becuase current in wires is regarded as positive charge flow the directions are actually opposite to each other.

(edited 8 years ago)

Reply 65

JoshF315

This might help a little: www.science-lounge.co.uk/circular-motion.html

Reply 66

JoshF315

Original post by tricky jj

Hey, I'm doing circular motion too! It is so confusing....

This might help a little: www.science-lounge.co.uk/circular-motion.html

Reply 67

Roryrow

Any of u guys writing IAL physics unit 4 in January?? Ive just started learning for it. Are the January papers tougher than those in June? Are the curves better????

Reply 68

shebby_7

https://43706519b25c85749d43dcee6dfc26eaddf4b294.googledrive.com/host/0B1ZiqBksUHNYZ3QzYUhOSGVzS0U/From-Edexcel-Set-1/4.4.2%20Capacitors.pdf could someone explain how the graph in question 3, figure 2? how does the capacitor charge instantaneously?

Reply 69

Konanabanana

Original post by shebby_7

This is because when charging current is not flowing through the resistor and so the only resistance is in the wire, thus negligible. This makes the time constant very small that's hwy the graph shows it charge instantly.

For discharging you connect a high resistance and thus u get a high time constant thus shows the exponential shape

Reply 70

Stephanie998

A2 physics empa people DM me we can discuss possible topics that may arise in the written task

(edited 7 years ago)

AQA have just released the 2015 papers, does anybody have the AQA Physics 2015 Unit 5 paper that was withdrawn?

Reply 73

thebrahmabull

I studied salters horners a2 book for understanding astrophysics. But thats for edexcel, but you may find it helpful. Also there are youtube videos which help in understanding. But use question papers and markscheme for deciding what you shoukd write in exam.

Reply 74

Billsonbubbles

Hi man,

I do some videos covering the A2 physics specification, and I have Astrophysics videos, and I will be uploading an Astrophysics Specification overview video.

Like the one I have for unit 4

https://www.youtube.com/playlist?lis...2obL7-dBYZobuo

Enjoy !!

Will

Reply 75

Billsonbubbles

Hello All,

Some of you may know me from doing the AS Physics specification overview videos,

Here is a Unit 4 one =}
https://www.youtube.com/playlist?lis...2obL7-dBYZobuo

I shall also be adding the Unit 5 specification overviews to this playlist as well.

So keep an eye out for those, they should be up within the week.

Enjoy !! And good luck in your exams,

Will

Reply 76

frxnkxe

would really appreciate any help with these questions