You are Here: Home >< Physics

# A-Level Physics - [Question] Watch

Announcements
1. 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?
2. That seems correct.
3. (Original post by JustasB)
That seems correct.
I got the answer it was just telling me it was wrong as I had

Thanks
I got the answer it was just telling me it was wrong as I had

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.
5. (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
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
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)
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.
8. (Original post by JustasB)
Use the same number of significant figures as given in the question.
okay thanks
9. Did you get these questions on Isaac physics because I have been set this board and I literally have no clue! Hell
10. (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
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
I got the answer it was just telling me it was wrong as I had

Thanks
How did you get the answer of 3.13? I've tried for a while but can't get it.
13. (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

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: February 8, 2017
Today on TSR

### How would you do in an Oxford interview?

Put yourself through the test

### STI without any sexual activity?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.