How Many Electrons Pass Through a Gold Wire Per Second?

AI Thread Summary
The discussion revolves around calculating the number of electrons passing through a gold wire carrying a current of 380 mA. The resistivity of gold is given, and initial calculations using resistance and voltage led to confusion regarding the correct approach. Participants emphasize that the current value directly relates to the number of electrons, with 1 A corresponding to approximately 6.241 x 10^18 electrons per second. It is noted that much of the provided information is irrelevant for solving the problem, and a simpler proportional calculation using the current is suggested. Ultimately, focusing on the current simplifies the solution process significantly.
victorializ
Messages
20
Reaction score
0

Homework Statement



The resistivity of gold is 2.44 x 10-8 Ω m at a temperature of 20°C. A gold wire, 0.5 mm in diameter and 44 cm long, carries a current of 380 ma. The number of electrons per second passing a given cross section of the wire, is closest to:

A) 2.4 × 10^18
B) 1.2 × 10^22
C) 2.8 × 10^14
D) 2.4 × 10^17
E) 6.3 × 10^15

Homework Equations



R=ρL/A

The Attempt at a Solution



R=(2.44 x 10^-8) (.44)/∏(.00025^2)
R= .0547
then i multiplied the resistance by the current (.38) to get .021 for a voltage.
then i divided that by (1.6 x 10^-19) and got 1.3 x 10^17 which isn't right but is close to the answer which is A
 
Physics news on Phys.org
Why did you divide a voltage by the electron charge? Do you expect the right unit "per second" as result of that calculation?

You are given the current. What does a current of 1 A (example value) mean?
 
victorializ said:

Homework Statement



The resistivity of gold is 2.44 x 10-8 Ω m at a temperature of 20°C. A gold wire, 0.5 mm in diameter and 44 cm long, carries a current of 380 ma. The number of electrons per second passing a given cross section of the wire, is closest to:

A) 2.4 × 10^18
B) 1.2 × 10^22
C) 2.8 × 10^14
D) 2.4 × 10^17
E) 6.3 × 10^15

Homework Equations



R=ρL/A

The Attempt at a Solution



R=(2.44 x 10^-8) (.44)/∏(.00025^2)
R= .0547
then i multiplied the resistance by the current (.38) to get .021 for a voltage.
then i divided that by (1.6 x 10^-19) and got 1.3 x 10^17 which isn't right but is close to the answer which is A

Something's off by a factor of 18.5 and you call that 'close'?

Learn that people are going to give you problems with a lot of irrelevant information!
 
mfb said:
Why did you divide a voltage by the electron charge? Do you expect the right unit "per second" as result of that calculation?

You are given the current. What does a current of 1 A (example value) mean?

so i need to use the fact that 6.241 x 10^18 electrons/sec pass through a circuit which is 1 A 

when i use that number though i still have it wrong so I'm not really sure where else my calculations are messed up.
 
victorializ said:
so i need to use the fact that 6.241 x 10^18 electrons/sec pass through a circuit which is 1 A 

when i use that number though i still have it wrong so I'm not really sure where else my calculations are messed up.

But the current isn't 1 A.
 
dauto said:
But the current isn't 1 A.

oh my goodness so most of the information in this problem is irrelevant? all i need is to do a proportion between 1A and the 38 mA in the problem?
 
victorializ said:
oh my goodness so most of the information in this problem is irrelevant? all i need is to do a proportion between 1A and the 38 mA in the problem?
If that gets you closer to the right answer, go for it! :smile:

380 mA would be even better ... :wink:
 
victorializ said:
oh my goodness so most of the information in this problem is irrelevant? all i need is to do a proportion between 1A and the 38 mA in the problem?
Yes (apart from the typo (?) NascentOxygen pointed out).
 
Back
Top