Field Force and Gravity

CONTENT

1. The Concept of Fields
2. Types of Fields
3. Properties of a Force Field
4. Acceleration Due to Gravity
5. Determination of Acceleration Due to Gravity
6. The Shape and Dimension of the Earth

The Concept of Fields

A field is a region under the influence of some physical agencies such as gravitation, magnetism and electricity.

Types of Fields

There are two types of field:

(i) Vector field

(ii) Scalar field.

Vector Fields

A vector field is that field which is usually represented by lines of force; while a scalar field is that field that is not represented by lines of force.

Examples of vector fields include gravitational field, magnetic field and electric field.

Examples of scalar fields include regions with distribution of temperature, density, etc.

(i) Gravitational Field

Gravitational field is a region of space or a force field surrounding a body that has the property of mass. In this region, any object that has mass will experience a force of attraction, called gravitational force.

Gravitational force is responsible for the fact that any object thrown up must definitely fall back. This force of gravity pulls every object towards the centre of the earth. That is to say, gravitational force causes a body which is not in contact with the earth to fall to the ground. This therefore means that the earth exerts an attractive force on every object either on it or near it.

Similarly, two objects of different masses exert equal and opposite forces of attraction on each other.

The radial field near a planet (e.g, earth) is shown below:

Magnetic field is a region around a magnet where it exerts force on other magnets. It is also a region where magnetic force is felt.

The patterns of the magnetic lines of force are shown below:

Magnetic Field Patterns

1. Field of a bar magnet:

   

2. Attraction between unlike poles:

   

3. Repulsion between like poles:

   

(iii) Electric Field

An electric field is a region around an electric charge where it exerts force on other charges. It is a field where an electric influence is felt.

The patterns of the electric lines of force are shown below:

1. Isolated positive and negative charge field lines:
   
2. Attraction between unlike charges:
   
3. Repulsion between like charges:
   

NP means Neutral Point. In this point, no electrical influence is felt.

EVALUATION

1. What is a field?
2. State the two types of field.
3. List the examples of vector field.
4. What is neutral point?