Electricity

Introduction

We use electricity in our day to day life. Have we ever wondered from where do we get this electricity? How does this electricity work?

2.1 Sources of Electricity

· Any device from which electricity is produced is called the source of electricity. We get electricity from different sources.

· The Major Electric power stations in Tamilnadu are:

o Thermal stations (Neyveli in Cuddalore District, Ennore in Thiruvallur District), Hydel power stations (Mettur in Salem District, Papanasam in Tirunelveli District), Atomic power stations (Kalpakkam in Kanchipuram District, Koodankulam in Tirunelveli District), and Windmills (Aralvaimozhi in Kanyakumari District Kayatharu in Tirunelveli District).

· Apart from these Solar panels which are prevalent in many places are used to produce electricity.

Let us discuss in short about working power stations.

1. Thermal Power stations

In thermal power stations, the thermal energy generated by burning coal, diesel or gas is used to produce steam. The steam thus produced is used to rotate the turbine. While the turbine rotates, the coil of wire kept between the electromagnet rotates. Due to electromagnetic induction electricity is produced. Here heat energy is converted into electrical energy.

2. Hydel power stations

In hydel power stations, the turbine is made to rotate by the flow of water from dams to produce electricity. Here kinetic energy is converted into electrical energy. Hydel stations have long economic lives and low operating cost.

3. Atomic power stations

In atomic power stations, nuclear energy is used to boil water the steam thus produced is used to rotate the turbine. As a result, electricity is produced. Atomic power stations are also called as nuclear power stations. Here nuclear energy is converted into mechanical energy and then electrical energy.

4. Wind mills

In wind mills, wind energy is used to rotate the turbine to produce electricity. Here kinetic energy is converted into electrical energy.

2.2 Cell

· A device that converts chemical energy into electrical energy is called a cell.

· A chemical solution which produces positive and negative ions is used as electrolyte.

· Two different metal plates are inserted into electrolyte as electrodes to form a cell.

· Due to chemical reactions, one electrode gets positive charge and the other gets negative charge producing a continuous flow of electric current.

· Depending on the continuity of flow of electric current cells are classified into two types. They are primary cells and secondary cells.

1. Primary Cells

They cannot be recharged. So they can be used only once. Hence, the primary cells are usually produced in small sizes. Examples cells used in clocks, watches and toys etc., are primary cells.

2. Secondary Cells

A cell that can be recharged many times is called secondary cell.

These cells can be recharged by passing electric current. So they can be used again and again. The size of the secondary cells can be small or even large depending upon the usage. While the secondary cells used in mobiles are in the size of a hand, the cells used in automobiles like cars and buses are large and very heavy. Examples Secondary Cells are used in Mobile phones, laptops, emergency lamps and vehicle batteries.

3. Battery

Often, we call cells as ‘batteries’. However only when two or more cells are combined together they make a battery. A cell is a single unit that converts chemical energy into electrical energy, and a battery is a collection of cells.

2.3 Electric Circuits

An electric circuit is the continuous or unbroken closed path along which electric current flows from the positive terminal to the negative terminal of the battery. A circuit generally has:

a) A cell are battery- a source of electric current

b) Connecting wires- for carrying current

c) A bulb- a device that consumes the electricity

d) A key or a switch- this may be connected anywhere along the circuit to stop or allow the flow of current.

a. Open Circuit

In a circuit if the key is in open (off) condition, then electricity will not flow and the circuit is called an open circuit. The bulb will not glow in this circuit.

b. Closed Circuit

In a circuit if the key is in closed (on) condition, then electricity will flow and the circuit is called a closed circuit. The bulb will glow in this circuit.

Types of Circuits:

1. Simple Circuit

2. Series Circuit

3. Parallel Circuits

1. Simple Circuit

A circuit consisting of a cell, key, bulb and connecting wires is called a simple circuit.

2. Series Circuit

If two or more bulbs are connected in series in a circuit, then that type of circuit is called series circuit. If any one of the bulbs is damaged or disconnected, the entire circuit will not work.

3. Parallel Circuit

If two or more bulbs are connected in parallel in a circuit, then that type of circuit is called parallel circuit. If any one of the bulb is damaged or disconnected the other part of the circuit will work. So parallel circuits are used in homes.

Symbols of Electric Components

In the circuits discussed above, we used the figures of electric components. Using electric components in complicated circuits is difficult. So, symbols of the components are used instead of figures. If these symbols used in electric circuits, even complicated circuits can be easily understood.

2.4 Conductors and Insulators

Will electric current pass through all materials? If an electric wire is cut, we could see a metal wire surrounded by another material. Do you know why it is so?

1. Conductors

The rate of flow of electric charges in a circuit is called electric current. The materials which allow electric charges to pass through them are called conductors. Examples: Copper, iron, aluminum, impure water, earth etc.,

2. Insulators (Non-Conductors)

The materials which do not allow electric charges to pass through them are called insulators or nonconductors. Examples: plastic, glass, wood, rubber, china clay, ebonite etc.,

Safety measures to safeguard a person from electric shock

I. Switch off the power supply.

II. Remove the connection from the switch.

III. Push him away using non - conducting materials.

IV. Give him first aid and take him to the nearest health center.