Examples

Coulomb's Law

Example 1       Answer

What is the magnitude of the force between two 3.60mC point charges that are 9.3 cm apart?

Example 2      Answer

Assume that you have 3 point charges on a line, left to right, of +75, +48 (in the center), and - 85 mC. The center one is 0.35 m from each of the others. What is the net force on each particle due to the other 2?

Example 3       Answer

If you rub a plastic ruler with a piece cloth it has the ability to pick up paper. Why?

Why is this ability enhanced on a dry day?

Example 4       Answer

We are not normally aware of the gravitational or electric force between two objects. Why? Give an example of a case where we do notice it.

 

Electric Field and Field Lines

 

Example 5       Answer

 

Assume that a proton is released in a uniform electric field. It experiences an electric force of 3.75x10-14 N toward the south. What is the magnitude and direction of the electric field?

 

Example 6       Answer

 

Given 3 particles with charges and locations as shown below. The angles (not shown) are

between r1 and r2 is q1

Between r2 and r3 is q2

Between r3 and r1 is q3

What is the magnitude and direction of the net force on particle C?

 

Example 7       Answer

 

Is the electric force a conservative force?

 

Example 8       Answer

 

The concept of a positive test charge is used in defining the electric field. Could we also use a negative test charge?

 

Example 9      Answer

 Calculate the magnitude of the electric field at point A by the  charges Q1 (positive, +20 mC) and Q2 (-20 mC).