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# Physics P3 watch

1. (Original post by bonbon)
I know you're right saying that they have high voltage and low current when moving electricity as this gives little resistance, so less energy wasted.

But Resistance = Voltage / Current. So surely a big voltage and small current gives more resistance since big/small = big. wouldn't small voltage/big current = small resistance?????

no thats to find the resistance of a component it wouldnt apply in this situation
2. ok thansk
3. and also the resistance is the amount of current allowed through; this resistance is what would cause heat in the lines but since there is little current anyway the resistance does affect it much.
4. so you shouldnt explain the use of low current using this equation as mighty grandiose did?
5. It is kind of a knock of effect since you are using a high voltage and low current it causes more resistance but because your using a low current in the first place it has little effect
6. Make that two of us?
7. what?
8. Ow yeah you can but i tried to put it more simpler what he said is right
9. hmmm.. bit confused but thanks anyway
hopefully it doesnt come up
10. why is an iron core used?

I thought first because it conducts + is magnetic and secondly because soft iron can be demagnetised (i.e. turned on and off)...?
11. The iron core is not used for electrical conductivity, only for its magnetic qualities.
12. I hate the mirrors and lenses. Does anybody have a website which explains it well?
13. (Original post by definite_maybe)
I hate the mirrors and lenses. Does anybody have a website which explains it well?
yeh i also hate the mirrors and lenses... plus basically the whole section on electromagnetism! the moments section seems ok though!
yeh i also hate the mirrors and lenses... plus basically the whole section on electromagnetism! the moments section seems ok though!
Yeah... I've learnt the rest. Just can't do those two sections.
15. Anyone got any predictions on which topics should come up? Hopefully not mirrors and lenses....
16. Yeah, I think they will come up as it is a big part of physics 3i
17. They're easy marks if you practise them and know how to do it.
18. Let me see if I have any blank pages, I drew some and copied them for me to practice on
19. Guys, I've drawn ray diagrams for the mirrors and lenses. I'll scan them in a minute and post them on here for you all.
20. Yay this is the bit I fail at, everything apart from Ray Diargams I'm pretty much ok on.

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Updated: June 13, 2008
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