1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question with large number?electron charge?

  1. Jul 31, 2009 #1
    Question with large number???electron charge?

    1. The problem statement, all variables and given/known data

    The electric charge of an electron is -1.6 x 10^-19 C. What is the force exerted between two electrons separated by one meter? Is it attractive or repulsive?

    2. Relevant equations

    F= K Q1Q2 / D^2

    3. The attempt at a solution

    Im horrible with large numbers and especially at negative exponents....so this is a guess

    K = 9x 10^9 N x m^2/c^2

    Q1 = -1.6 x 10^-19 C
    Q2 = -1.6 x 10^-19 C
    D= 1 m


    F= 9 x 10 ^9 N x m^2 X ( -1.6x 10 ^-19 C x -1.6x 10 ^-19 C / 1^2 m)

    F= 9 x 10 ^9 N x m X (3.2 x 10^19 C^2 )
    F= 28.8 x 10^28 NxmxC^2.....is the answer i got....

    I know i am completely off but how can i do this ...this is basically math but im just not with well large numbers...
     
  2. jcsd
  3. Jul 31, 2009 #2

    rl.bhat

    User Avatar
    Homework Helper

    Re: Question with large number???electron charge?

    F= 9 x 10 ^9 N x m X (3.2 x 10^19 C^2 )
    This step is wrong. -1.6x10^-19 X -1.6x10^-19 = ?
     
  4. Jul 31, 2009 #3
    Re: Question with large number???electron charge?

    Thats the thing i dont know...do you add the exponents together??

    2.56 x 10^-38????

    1.6 x 1.6 = 2.56 but what about the 10^-19? do i add them or does it stay the same????

    Actually now i got 2.6 x 10 ^-38...by multiplying both
     
    Last edited: Jul 31, 2009
  5. Aug 1, 2009 #4

    rl.bhat

    User Avatar
    Homework Helper

    Re: Question with large number???electron charge?

    This is correct.
     
  6. Aug 1, 2009 #5

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: Question with large number???electron charge?

    Yes, you add the exponents when you are multiplying two numbers.

    Do you have a calculator that you can double-check things like this? If not, Google can be used as a calculator:

    http://www.google.com/#hl=en&q=1.6e...aq=f&oq=1.6e-19+*+1.6e-19&aqi=&fp=MyO-rnw0Pu0

    Note the computer-standard "e-19" to signify "×10-19 "
     
  7. Aug 1, 2009 #6
    Re: Question with large number???electron charge?

    Ok so after i have 2.6 x 10^-38 is it C^2?
     
  8. Aug 1, 2009 #7
    Re: Question with large number???electron charge?

    Well let me put what i have..... F=9 x 10^9 N x m^2/c^2 X( 2.6 x 10^-38 c^2 /1 m^2)

    that is what i have...do i cancel out the m^2 and c^2? from both sides? so that only the N is remaining?
     
  9. Aug 1, 2009 #8

    rl.bhat

    User Avatar
    Homework Helper

    Re: Question with large number???electron charge?

    Yes. Force should be in N.
     
  10. Aug 1, 2009 #9
    Re: Question with large number???electron charge?

    Cool so if i did my calculations right....i got 2.3 x 10^-28 N am i close or am i really off? but i think this force is repulsive no??? because its a positive number .......or is it attractive?
     
  11. Aug 1, 2009 #10

    rl.bhat

    User Avatar
    Homework Helper

    Re: Question with large number???electron charge?

    Like charges repel each other.
     
  12. Aug 1, 2009 #11

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: Question with large number???electron charge?

    Exactly. The equation gives the magnitude of the force. Use the opposites attract / likes repel rule to figure out the direction.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Similar Discussions: Question with large number?electron charge?
  1. Charge of an electron (Replies: 2)

  2. Number of electrons (Replies: 1)

Loading...