PHSC 111 - Introduction to Physical Science

Coulomb's Law

Every charge is attracted to or repelled by every other charge. This electric force is proportional to the amount of charge and inversely proportional to the square of the distance between the charges. This relationship is known as Coulomb's Law.

Procedure:

1. Go to the following website: https://phet.colorado.edu/.Search for Coulomb's Law (HTML5). Click Play and then Macro Scale.Be sure that the box next to Force Values is checked.
2. Note that the units for charge are C, which means micro-Coulombs (1 C = 0.000001 C).
3. Click and drag on one or both charges to change the distance between them. Take some time to familiarize yourself with the simulation. Notice how forces change as charges change and as distance changes. Be sure to pay attention to the direction of the forces (attractive or repulsive).
4. Complete the table below. You may choose the charges of each object and the distance between them. Be sure that your trials include changes to at least one variable and controls for the others. For example, change the charges while keeping distance constant (relative to another trial) and then vice versa. An example has been done for you. Include at least 4(four) trials. (Hint: You might want to review the questions below for ideas about what masses and/or distances to use.)

Charge 1 (C)	Charge 2 (C)	Distance (cm)	Do the charges attract or repel?	Force on q1 by q2 (N)	Force on q2 by q1 (N)
-4	8	3	Attract	319.6	319.6

Questions:

1. Which of the following applies to electric force? Mark all that apply:

1. Opposites repel
2. Opposite attract
3. Likes repel
4. Likes attract

2. Newton's 3^rd Law tells us that in the electric force that exists between a large charge and a small charge, the force on the large charge is greater than / equal to / less than the force on the small charge.

3. As the distance between charges decreases, electric force increases / decreases. (choose one)

4. Doubling the amount of both charges would result in a change of force between the charges of 8x / 6x / 4x / 2x / no change / x / x / 1/6x / 1/8x. (choose one)

5. Tripling the distance between two charges would result in a change of force between the charges of 9x / 6x / 3x / no change / 1/3x / 1/6x / 1/9x.(choose one)

6. Coulomb's Law shares similar characteristics to which other law?

1. Newton's Law of Universal Gravitation
2. Newton's 2^nd Law of Motion
3. Law of Conservation of Energy
4. Law of Inertia