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# A2 Physics Question - fields watch

1. http://filestore.aqa.org.uk/subjects...2-QP-JUN15.PDF

Question 2 (c) i

I haven't a clue where they've got the formula used in the markscheme from, so any help would be greatly appreciated.

Cheers
2. (Original post by iMacJack)
http://filestore.aqa.org.uk/subjects...2-QP-JUN15.PDF

Question 2 (c) i

I haven't a clue where they've got the formula used in the markscheme from, so any help would be greatly appreciated.

Cheers
Two ways:

1) Standard formula way:

Electric potential is defined to be

by rearranging. Select a value of V and r from the graph and substitute.

2) Notice from the formula above, if you have a graph of V against 1/r, then the gradient will be . Work out the gradient and multiply by .
3. (Original post by kingaaran)
Two ways:

1) Standard formula way:

Electric potential is defined to be

by rearranging. Select a value of V and r from the graph and substitute.

2) Notice from the formula above, if you have a graph of V against 1/r, then the gradient will be . Work out the gradient and multiply by .
Ahhh! A simple re-arragement, how have I missed that! Oops!

Thanks a bunch, also the second method is interesting and good for understanding it more too.

Cheers

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