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A-Level Physics - [Question]

How many electrons flow past a point each second in a 5.0mA electron beam?
I used I=Q/T
I = 0.005 A
Q =
T = 1
so Q = 0.005 C
right?

That seems correct.

Original post by JustasB

That seems correct.

I got the answer it was just telling me it was wrong as I had
3.13 instead of 3.1

Thanks

Reply 3

JKING>)

Original post by AdeptDz

I got the answer it was just telling me it was wrong as I had
3.13 instead of 3.1

Thanks

The answer was to 2 significant figures, so the answer of 3.13 is correct but it should be rounded to the correct number of significant figures.

Reply 4

AdeptDz

Original post by JustasB

The answer was to 2 significant figures, so the answer of 3.13 is correct but it should be rounded to the correct number of significant figures.

Thanks
Do you have an idea on this question:
Alpha particles have twice the charge of an electron. What is the current caused by a radioactive source which emits 3000 alpha particles per second, to 3 significant figures?

First I found out the charge which is 3.2*10^-19 (For one alpha particle) then I multiplied it by 3000 to get charge for 3000 alpha particles which is 9.6x10^-16 C now i used I = Q/T
so I would equal 9.6 x 10^-16 aswell but i'm not sure what to do now or what i done wrong as this answer is incorrect

Reply 5

AdeptDz

Original post by AdeptDz

oh wow, it is correct just not to 3 sig. fig. once again.
Keep making the same mistake, my bad!

Edit:
Do you know if i have to always use correct sig. fig. in the exam? (AQA if it helps)

(edited 7 years ago)

Reply 6

JKING>)

Original post by AdeptDz

oh wow, it is correct just not to 3 sig. fig. once again.
Keep making the same mistake, my bad!

Edit:
Do you know if i have to always use correct sig. fig. in the exam? (AQA if it helps)

Use the same number of significant figures as given in the question.

Reply 7

AdeptDz

Original post by JustasB

Use the same number of significant figures as given in the question.

okay thanks

Reply 8

Mossie99

Did you get these questions on Isaac physics because I have been set this board and I literally have no clue! Hell

Reply 9

AdeptDz

Original post by Mossie99

Did you get these questions on Isaac physics because I have been set this board and I literally have no clue! Hell

Ye I did ; was a while back though

Posted from TSR Mobile

Reply 10

Mossie99

Original post by AdeptDz

Ye I did ; was a while back though

Posted from TSR Mobile

Found out I was doing the same mistake as you with my sig figs! Gets very frustrating when it continuously says incorrect! Thanks anyway

Reply 11

Elementa

Original post by AdeptDz

I got the answer it was just telling me it was wrong as I had
3.13 instead of 3.1

Thanks

How did you get the answer of 3.13? I've tried for a while but can't get it.

Reply 12

AdeptDz

Original post by Elementa

How did you get the answer of 3.13? I've tried for a while but can't get it.

Charge / Charge on an electron
0.005/1.6x10^(-19)
I'm guessing that is what I done
and that gives you 3.13x10^16

Sorry for the late reply

Reply 13

madonedm

Original post by AdeptDz

How many electrons flow past a point each second in a 5.0mA electron beam?
I used I=Q/T
I = 0.005 A
Q =
T = 1
so Q = 0.005 C
right?

But I was doing this question on Isaac physics and it said that this answer was incorrect. Any advice?

Reply 14

madonedm

Original post by JKING>

The answer was to 2 significant figures, so the answer of 3.13 is correct but it should be rounded to the correct number of significant figures.

Hi, I put 3.1 as the answer do you possibly know what I might be doing wrong?

Reply 15

Tom-valley24

Hi there everything you have done so far is absolutely perfect, there is just another part that needs to be applied to find the number of electrons passing each point each second. You have correctly calculated the charge passing each second, but in order to find the number of electrons you have to divide your 0.005 by 1.60x10^-19, which is the charge of an electron in coulombs. This will give how many electron flow per second.

Reply 16

152355

I have just been doing this question and none of the answers from above are correct not sure what to do now

Reply 17

GabiAbi84

Original post by 152355

I have just been doing this question and none of the answers from above are correct not sure what to do now

The original question?
What answer have you given?

Reply 18

152355

The question is: How many electrons flow past a point each second in a 5.0mA electron beam?I have tried all the answers from above and none of them are right