INTRODUCTION TO CIRCUIT

All branches of electrical engineering are based on electric circuit theory and electromagnetic theory. Several branches of electrical engineering such as Power System, Control System, Electrical Machine, Instrumentation, Electronics, Communication are based on electric circuit theory. Therefore, basic electric theory course is very important course for an electrical engineering and of course an excellent starting point for a first semester students in Electrical Engineering. Circuit Theory course is also very important to students specializing in other branches of the physical sciences because of applied mathematics, physics, and topology involved. Also circuits are a good model for study of energy systems.

In Electrical Engineering, we are often interested in transferring energy from one point to another. To do this, we require an interconnection of electrical devices and such interconnection is known as an electric circuit. Each component of the electric circuit is known as an element. Therefore, an electric circuit is an interconnection of electrical element.

Electrical charge(electrons) will flow through the circuit due to chemical forces in the battery. The charge gain energy from the chemicals in the battery and delivers energy to the lamp. The battery voltage is a measure of the energy gained by unit of charge as it moves through the battery.

The wires are made of copper conductor and are insulated from one another by electrical insulation coating. Electrons readily move through the copper conductor but not through the plastic insulation.

The switch is used to allow or disallow the flow of current through the circuit. Current will flow through the circuit when the conducting metallic parts of switch make contact and we say that the switch is closed. On the other hand, when the conducting parts of the switch don't make contact, current doesn't flow through the circuit and we say that switch is open.

The lamp contains Tungsten wire that can withstand high temperature. The Tungsten is not as good as copper, and the electrons experience collisions with the atoms of the Tungsten wires, resulting in heating of the Tungsten. We can say that Tungsten wire has electrical resistance. Thus energy is transferred by the chemical action in the battery to the electrons and then to the Tungsten where it appears as heat. The Tungsten becomes hot enough so that light is emitted.