Page 185 - WCS - Electrical

WORKSHOP CALCULATION & SCIENCE - CITS

EXERCISE 18 : Electricity

Heat & Temperature
Electricity is a kind of energy. It is the most useful sources of energy which is not visible but its presense can be
felt by its effects. Electricity is obtained by conversion of other forms of energy like heat energy, chemical energy,
nuclear energy, mechanical energy and energy stored in water etc.,
To understand electricity, one must understand the structure of an atom.
Basically an atom contains electrons, protons and neutrons. The protons and neutrons are located in the centre
of an atom and the electrons, a negative electric charge particle revolving around the nucleus in an atom. The
proton has a positive charge. Neutrons are neutral and have no charge.
Sources of electricity
Battery

Battery stores electrical energy in the form of chemical energy and it gives power when required. Battery is used
in automobiles and electronics, etc.,
Generator
It is a machine which converts the mechanical enregy into electrical energy.

When a conductor rotates between a magnetic field using prime mover an emf will be induced. By using this
method all types of AC and DC generator - generates power.
E.g. Thermal power station

Hydro power station
Nuclear power station
Wind power station
Solar power station
Thermo couple

If two dissimilar pieces of metals are twisted together and its joined end is heated in a flame, then a potential
difference or voltage will be induced across the ends of the wires. Such a device is known as a Thermo couple.
Thermo couple is used to measure very high temperature of furnaces.
Effects of electric current
When an electric current flows through a medium, its presence can be felt by its effects, which are given below.
1 Physical effect
Human body is a good conductor. when the body touches the bare current carrying conductor, current flows
through the human body to earth and body gets severe shock or cause even death in many cases.
2 Magnetic effect
When an electric current passes through a coil, a magnetic field is produced around it.

E.g. : Electromagnet Motor, Generator, Electric bell
3 Chemical effect
When an electric current passes through an electrolyte, chemical action takes place. Because of that, an electrical
energy is stored in a battery as a chemical energy.

E.g.: Electroplating, Cells and battery charging, refining of metals etc.,
4 Heating effect
When an electric current passes through any conductor, heat is produced in the conductor due to its resistance.

172