Experiments and studies on what makes up matter resulted in the formulation of the modern theory of atoms. The theory consists of the following:
1. All matter is made up of tiny, invisible particles called atoms.
2. The atom is composed of negatively charge particles called electrons (-), positively charged particles called protons (+), and neutrally charged neutrons which carry no charge (N).
3. Protons and neutrons have the same mass and are about 1,830 times as heavy as electrons.
4. Every proton carries a unit charge of positive electricity; every electron carries a unit charge of negative electricity.
5. The Atom of any element contains exactly the same number of protons and electrons, thus the atom is said to be electrically neutral.
6. The dense central portion of the atom, the nucleus, is made up of all the protons and the neutrons. Thus, the positive charge of the atom is concentrated in the nucleus.
7. Electrons resolve around the nucleus in one or more shells or rings at various distances.
8. The entire chemical characteristics of atom depend largely upon the number of electrons that it has and how these electrons are arranged.
Scientists also advance the theory that electricity is a flow of electrons. This is known as the Principle of Electricity or the Electron Theory. The theory further states that in an electric circuit, electrons flow from the negative to the positive terminal. The theory also states that when electrical pressure is applied in an electric circuit, the electrons in an atom move to another atomic body, thus, creating the flow of electricity. The electrons flow only when the circuits are closed or completed.
Electrical Power System
The flow of electrons between two charged bodies is cause by an electromotive force (emf). To measure a potential difference, two points are necessary. Voltage is the potential difference between these two points. The points in an electrical system are the sources of energy and the work-producing device or the load. These two points are connected by lines or wires.
Current is the flow of electric energy. The flow is from the source through the lines, to the load and then back to the source. This system is known as Direct Current (DC) because the flow of current is always in the same direction. This kind of current is produced by batteries and generators.
AC stands for Alternative Current which means that the current flow changes its direction periodically. In this system, the AC flows in repeated cycles where the current starts, rising to a maximum and then drops to zero, reverses direction and repeats the cycle as long as the circuit is on. This is usually produced by generators in big power plants.
The Term frequency describes the number of complete cycles performed in one second such that one cycle per second equals one hertz.
The flow of current passing on a circuit at a given time is measure by an ammeter using the unit ampere.
Resistance is the force which opposes and reduces the flow of electric current. It is measure in ohms.
Although resistance is used to control the amount of electric current which flows in a circuit, it can also be overcome by a more powerful source.
Power refers to the amount of work done by electrical energy at a given time to make a load work. It is the product of voltage and current and is measured in watts.