How to find the number of excess electrons?

  • Thread starter Thread starter pebbles
  • Start date Start date
  • Tags Tags
    Electrons
Click For Summary
SUMMARY

The discussion focuses on calculating the number of excess electrons on a ball with a charge of -4.00 x 10^-17 C. The correct method involves dividing the total charge by the charge of a single electron, which is 1.60 x 10^-19 C. The accurate calculation yields 2.5 x 10^2 electrons, confirming that charge is quantized and must be a multiple of the elementary charge. Participants clarified the division of powers of ten and the significance of negative exponents in this context.

PREREQUISITES
  • Understanding of electric charge and its quantization
  • Familiarity with the concept of elementary charge (e)
  • Basic knowledge of scientific notation and powers of ten
  • Proficiency in performing arithmetic operations with scientific notation
NEXT STEPS
  • Review the concept of charge quantization and its implications in physics
  • Learn how to perform arithmetic operations with scientific notation
  • Study the relationship between charge, electrons, and elementary charge (q = ne)
  • Explore problems involving electric charge calculations in electrostatics
USEFUL FOR

Students studying physics, particularly those focusing on electrostatics and charge calculations, as well as educators looking for clear explanations of charge quantization and scientific notation.

pebbles
Messages
95
Reaction score
0

Homework Statement



How many excess electrons are on a ball with a charge of -4.00*10^-17 C?

Homework Equations


I know that the charge per electron is 1.60 *10^-19C.


The Attempt at a Solution



My textbook does not explain how to do this, but I thought I would divide-->4.00*10^-17 C * 1 electron/-1.60*10^-19. I got -2.5*10^-36. The answer from the book is 2.5*10^2 electrons.
I did some messing around and did this-->4.00*10^-17C*1 e/1.60*10^19C=2.5*10^2 electrons.
What's the correct way to do this problem?
Thanks in advance.
 
Physics news on Phys.org
Your set-up is right and the units will check. But how do you divide

4.0 x 10^-17 / 1.6 x 10^-19 ?

What is 1 / 1.6 x 10^-19 ?

(In fact, your check is also incorrect. You may want to review how division works with powers of ten and what negative exponents mean. 10^-17 / 10^-19 = 100 ; 10^-17 / 10^19 = 10^-36 .)
 
uhh, I'm confused....?
 
You're dividing by 1.6 x .0000000000000000001 . So 4 / 1.6 is 2.5 , but what is

10^-17 / 10^-19 =

0.00000000000000001 / 0.0000000000000000001 ?
 
oh i see!
10^-17/10^-19=100
so therefore 2.5*10^2.
thanks so much! :D
 
Charge is quantized so the excess charge has to be a multiple of e (elementary charge)

q=ne, where n is the number of electrons.

That's why it works I believe since your textbook didn't explain it.
 
  • Like
Likes   Reactions: HRubss

Similar threads

  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
12
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
9K
Replies
5
Views
4K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 8 ·
Replies
8
Views
5K