3.2 Electric Charge

3.2 Electric Charge

Electric Charge

Electric charge is a fundamental property of subatomic particles. There are two types of charges:

• Positive (e.g., protons).

• Negative (e.g., electrons).

The amount of charge can be measured in:

• Coulombs (C): For larger charges.

• Elementary Charges (e): For smaller charges (e.g., atomic scale).

Law of Electrostatics

Likes repel, opposites attract.

• Positive (+) charges repel other positive charges.

• Negative (−) charges repel other negative charges.

• Positive and negative charges attract each other.

Try exploring this concept with the PhET simulation, where a charged balloon sticks to a sweater and a wall!

Key Concepts in Electrostatics:

1. Coulomb’s Law:

   • Describes the force between two charges:

   • (Coulomb constant).

   • and : Charges.

   • : Distance between charges.

2. Electric Force:

   • Force exerted between charges.

   • Can be attractive or repulsive.

3. Electric Field:

   • A region where a charge experiences force.

   • Strength is determined by the force on a test charge.

4. Electric Potential:

   • Measure of potential energy per unit charge in an electric field.

   • Often measured in volts (V).

5. Electric Potential Energy:

   • Stored energy due to electric charges.

   • Work done to move charges in an electric field.

6. Electric Flux:

   • Measure of electric charge flow through a surface.

Attraction and Repulsion

Practice Questions

Question 1:

A metal paper clip is attracted to a positively charged metal ball. What could be the charge on the paper clip?

Answer:

• Negative or neutral. A positively charged ball attracts both negatively charged and neutral objects.

Question 2:

Two charged particles are separated by a distance of 1 meter. The first particle has a charge of +3 C, and the second has a charge of −4 C. What is the electric force between the particles?

Solution: Result: The electric force is , indicating attraction.

Question 3:

A charged particle with a charge of +2 C is placed in an electric field of 100 N/C. What is the electric force on the particle?

Solution: Result: The electric force is 200 N.

Question 4:

A charged particle with a charge of +3 C is placed in an electric field of 200 N/C. What is the electric potential at the particle’s location?

Solution: Result: The electric potential is 600 N/C.

Understanding these principles of electric charge is essential for exploring electric fields, circuits, and electromagnetism. Continue practicing with these concepts to build a strong foundation!