Fields
A field is a region or space within which an effect can be felt.
We can play the game of football in a football field with all the rules obeyed. Here the ball is the target.
In the same vein, on the surface of the earth, we can feel the effect of gravitational force in the presence of masses. We also feel the effect of magnetic force in the presence of steel needles. And electric force in the presence of charges.
Electric field
Like bodies repel and unlike bodies attract. The space through which the electric force can be detected is called electric field or a space within which we feel the effect of a charge (s).
Lines of force
An electric line of force is an imaginary curve drawn in such a way that tangent to this curve at any point gives the direction of the electric field at that point. It can be a path with maybe a curve or a straight line.
Properties of lines of force
1. No lines of force originate or terminate in the space surrounding a charge.
2. Every line of force in an electric field is a continuous line terminated by a +ve at one end and –ve at the other end.
3. Lines of force never intersect.
4. In a uniform field, the lines of force are straight, parallel and uniformly spaced.
5. Lines of force are usually curves.
Electric current
Electricity flows through some materials known as conductors, e.g. metals such as mg, Au, Fe etc. Their atoms are surrounded by loosely held electron clouds. Electricity is brought about by the flow of electrons.
Insulators
They are poor conductors of electricity. Their electrons are not allowed to move freely due to the fact that these electrons are held tightly and closely to their atoms.
To differentiate between conductors/insulators
If the material closing the gap, AB in the 1st design is a conductor, then the bulb will light, and does not light when there is an insulator.
Some liquids like methylated spirit, oil are insulators and as such will not light the bulb when used in the beaker. But when acid or salt is used it lights. Electricity is the flow of electrons or flow of charges.
Production of electric current
This can be produced in many ways;
a. Chemical energy
b. Heat energy
c. Mechanical energy
d. Solar energy
Chemical energy
Chemical energy can be used to generate electricity e.g. in torches, radio sets etc. Cells are used for this purpose. The set up can be used to generate electricity in the conductor.
