# Question with large number???electron charge?

by graphicer89
Tags: charge, numberelectron
 P: 55 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...
 HW Helper P: 4,436 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 = ?
P: 55
 Quote by rl.bhat F= 9 x 10 ^9 N x m X (2.56 x 10^19 C^2 ) This step is wrong. -1.6x10^-19 X -1.6x10^-19 = ?
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

HW Helper
P: 4,436

## Question with large number???electron charge?

 Quote by graphicer89 Thats the thing i dont know...do you add the exponents together?? 2.56 x 10^-38???? Actually now i got 2.6 x 10 ^-38...by multiplying both
This is correct.
Mentor
P: 11,958
 Quote by graphicer89 Thats the thing i dont know...do you add the exponents together??
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:

Note the computer-standard "e-19" to signify "×10-19 "
P: 55
 Quote by rl.bhat This is correct.
Ok so after i have 2.6 x 10^-38 is it C^2?
 P: 55 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?
HW Helper
P: 4,436
 Quote by graphicer89 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?
Yes. Force should be in N.
P: 55
 Quote by rl.bhat Yes. Force should be in N.
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?
HW Helper
P: 4,436
 Quote by graphicer89 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?
Like charges repel each other.
Mentor
P: 11,958
 Quote by rl.bhat Like charges repel each other.
Exactly. The equation gives the magnitude of the force. Use the opposites attract / likes repel rule to figure out the direction.

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