October 10, 2015

Homework Help: Static Electricity. 11th Grade Pre-AP Physics

Posted by Angela on Friday, February 25, 2011 at 2:08pm.

Hi everyone! I need some help studying for a test on Static Electricity.

I have a few review questions that I don't know how to do. Below they are numbered and in parenthesis I answered what I think you might have to do to get the answer. Please help me in any way you can. Your help is much appreciated! =)

1. What is the value of a charge of a body that carries 20 excess electrons?

(For number 1, I think that the question asks you to pretend that something is negatively charged by 20 electrons. So I think you take the charge of an electron, which is 1.6 x 10^-19, and multiply it by 20. If you do that, the answer is 3.2 x 10^-18.)

2. Two like charged balloons, placed at a distance of .5 meters, experience a repulsive force of .32 N. What is the force if the distance between the two balloons is doubled?

(For number 2, if you use Coulomb's Law, the equation used to find .32 N was Force = the constant of K multiplied by the product of the charges divided by the square of the distance. Therefore, I think to solve this, you need to double r, which would mean that force is one-fourth of what it originally was. Following that, I think you divide .32 N by 4 and the answer would be .08 N.)

3. What is the force between two small charged spheres that have charges of 2 x 10^-7 and 3 x 10^-7 if the distance of r is 30 cm.

(For number 3, I think you use Force = the constant of K multiplied by the product of the charges divided by the square of the distance again. If you plug in the numbers, you would get 6 x 10^-7. I am almost sure this is right, if you could please plug in the numbers and let me know if this is the answer because for some reason I can never get the right numbers even if I follow the right steps.)


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