Force Between Charges

Key Concepts

• The force between the charges
• Force of attraction between the charges
• Force of repulsion between the charges
• Conductors, insulators and semiconductors

Introduction: Force Between Charges

The force between the charges  

Consider an electric field in which two charges, q₁ and q₂, are at the distance d from each other. 

Coulomb inverse square law: 

Coulomb inverse square law states that charges which are present in the same electric field experience attraction or the repulsion force.  

The force in the electric field is directly proportional to the charges present and inversely proportional to the square of the distance between them. 

Consider k=1 

The units of the force are coulomb²/meter² 

Which is also written as C²/m² 

Points to be remembered in coulomb inverse square law: 

1. Both charges that experience force should have the same electric charge. 

2. There may be both positive or the both negative charges.  

3. The distance between the charges is always measured in the square.  

4. Force doesn’t have SI unit Newton in the inverse square law. 

Coulomb’s inverse law if the charge has opposite charges: 

The negative sign is added as the charges are opposite to each other, and the charges have the force of attraction. 

Coulomb’s inverse law if the charge has same charges: 

The positive sign indicates that the charges are the same and have a force of repulsion. 

Conductors:  

Substances or the objects which allow electricity to pass through them completely are called conductors.  

Examples: 

1. Iron 

2. Copper 

3. Aluminum  

Semi-conductors: 

Substances or objects that allow electricity to pass through them are partially called semi-conductors. 

Examples: 

1. Silicon 

2. Germanium  

Insulators: 

Substances or objects which doesn’t allow electricity to pass through them are called insulators  

Examples: 

1. Rubber 
2. Plastic

Summary:

Coulomb inverse square law states that charges present in the same electric field experiences attraction or the repulsion force.

The force in the electric field is directly proportional to the charges present and inversely proportional to the square of the distance between them.

The units of force are coulomb²/meter

Which is also written as C²/m²

Points to be remembered in coulomb inverse square law:

1. Both charges that experience force should have the same electric charge.
2. There may be both positive or both negative charge.
3. The distance between the charges is always measured in the square.
4. Force doesn’t have SI unit Newton in the inverse square law.

Conductors:

Substances or objects which allow electricity to pass through them completely are called conductors.

Semiconductors:

Substances or objects that allow electricity to pass through them are partially called semiconductors.

Insulators:

Substances or objects which do not allow electricity to pass through them are called Insulators.