Homework Help: Electric current? how many electrons?

1. Jan 5, 2012

snash1057

1. The problem statement, all variables and given/known data
A net charge of 49 mC passes through the cross-sectional area of a wire in 12.0 s

(a) What is the current in the wire?
_4.1E-3_ A

(b) How many electrons pass the cross-sectional area in 1.0 min?
______electrons

2. Relevant equations

I=Q/t

3. The attempt at a solution
part A was very simple, 49E-3/12 = 4.1E-3 amps

however part b i do not understand.

1 electron = 1.6E-19 and 1 coulumb = 6.24E18

49E-3 x 6.24E18 = 3.06E17 x 60 = 1.8E19 incorrect

49E-3 x 1.6E-19 = 7.84E-21 x 60 = 4.7E-19 incorrect

2. Jan 5, 2012

technician

You need to realize that 1amp means 1 coulomb per second.
Current is the rate of flow of electric charge

3. Jan 5, 2012

snash1057

if i am sort of understanding what you are saying, you mean to use my answer for part a in order to get my answer for part b?

well i have tried something like that, but i still must be off track because i still got it wrong

4.1E-3 x 6.24E18 = 2.56E18 x 60 = 1.5E18 incorrect

4. Jan 5, 2012

technician

You have the current to be 4.1 x 10^-3A which means 4.1 x 10^-3 coulombs per second.
The charge on 1 electron is 1.6 x 10^-19 coulombs so how many electrons per second.
Be careful the question asks for how many in 1MINUTE

5. Jan 5, 2012

snash1057

if i have 4.1E-3 c/s then wouldnt i have to multiply that by the one electron?

4.1E-3 x 1.6E-19 = 6.56E-22

but like you said since it is one minute and there are 60 seconds in a minute i would multiply 6.56E-22 by 60 in order to get 3.9E-20

im sorry for all this, but im just really confused haha :)

6. Jan 5, 2012

technician

To find how many electrons you do not multiply !!!!!!!!