The Student Room Group

Isaac Physics questions

Can anyone help with these two questions?

If a 50𝜇A current is flowing then how many electrons pass a point each minute to 2 significant figures?


How long does it take for a current of 6.0A to deliver 1.5×10 (to the power of)17 Cu2+ ions in a solution? Assume these ions are the only charged particles moving.
Original post by hilary08
Can anyone help with these two questions?

If a 50𝜇A current is flowing then how many electrons pass a point each minute to 2 significant figures?


How long does it take for a current of 6.0A to deliver 1.5×10 (to the power of)17 Cu2+ ions in a solution? Assume these ions are the only charged particles moving.

Start with a basic definition of the amp, that tells you how much charge per sec is needed to carry 1A. Now scale that to 50uA and then think about how that is related to the charge on a single electron.
Reply 2
Original post by Mr Wednesday
Start with a basic definition of the amp, that tells you how much charge per sec is needed to carry 1A. Now scale that to 50uA and then think about how that is related to the charge on a single electron.

Well I know that the charge on a single electron is 1.6x10^-19. So I used Q = It so Q=50uA x 60s = 3C and then I divided 3C by 1.6x10^-19 to get 1.875x10^-19 ....I'm so confused
1 Amp is 1/1.6E-19 electrons per second... i.e. a lot of electrons per second

50uA is only 50 millionths of that number - and still a lot of electrons per second

TBH you should be thinking about what your answers mean 1.875x10^-19 electrons per minute is one electron in billions of years and should be clear that it's an error.
Original post by hilary08
Well I know that the charge on a single electron is 1.6x10^-19. So I used Q = It so Q=50uA x 60s = 3C and then I divided 3C by 1.6x10^-19 to get 1.875x10^-19 ....I'm so confused

do it again but read your calculator properly

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