Electricity

This is a form of energy that is produced by moving electrons or electrical charges. There are two types of charges; positive charges and negative charges.

Sources of electricity

Some examples of sources of electricity are:

• batteries (torch and car batteries)
• bicycle dynamos
• hydro-electric generators
• petrol and diesel driven generators
• wind driven turbines
• geothermal generators
• solar energy (panels)

 Forms of electricity

• static electricity
• Current electricity

Static electricity

It is a type of electricity whose charge do not move. It produced when two nonconductors are rubbed together such as plastic ruler and hair.

Lightning

Is an application of static  electricity.

It is produced when positively and negatively charged clouds meet causing a spark of light (lightning).

The thickened air expand and vibrates vigorously producing sound or thunder.

NB. Lightning and thunder takes place almost simultaneously by lightning is seen first because light moves faster than sound.

Dangers of lightning

Lightning produces a lot of electrons and heat that can burn objects like houses and organisms such as cattle and human beings

Avoiding being hit by lightning

• Close windows and doors.
• Don’t take a bath or shower during a thunderstorm, especially if you’re out in the countryside where homes and lines of communication are not as well protected against lightning.
• Don’t light a stove or fireplace – the smoke coming out of a chimney has high conductivity and increases the likelihood that lightning will strike your home.
• place lightning conductors on the buildings

 Lightning conductor

It protects the building against lightning by conducting electrons to the ground. It is made of sharp copper arrestors on the top of the building and a thick copper wire conductor to the ground.

Current electricity

This is a kind of electricity that moves through wires in form of electron.

Sources of current electricity

These include Car batteries, bicycle dynamo, hydroelectricity generators, thermos generators, wind driven turbines, solar panels.

Hydroelectricity is the cheapest and most reliable source of current electricity.

Uses of current electricity

• Cooking
• Ironing
• Powering of radios and television
• Refrigerators
• Running of industrial equipment

Electric circuit

An electrical circuit is a path or line through which an electrical current flows to allow electric appliance work.

A simple circuit consists of a bulb, copper wires, a battery or two batteries and a switch.

Symbols may be used to represent the components of a circuit. These symbols are shown below.

Electricity in a circuit flows from the positive terminal of battery/dry cells all around the circuit and back to the negative terminal of the battery. A simple electric circuit is shown below:

Importance of components of a circuit

• Battery or dry cell generate current in the circuit
• Bulb gives out light and heat
• Switch breaks and completes the circuit as required
• The fuse breaks the circuit in case of short circuit or voltage overload protecting electrical devices against overloads and short circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby interrupting the current.

Good and bad conductors of electricity

Good conductors are materials that allows electricity to pass through them easily; examples are metals and graphite.

Poor conductors of heat allow small amount of heat.

Bad conductors of heat are materials that do not allow electricity to pass through. They are also called insulators, e,g. wood, paper, clothes and plastic.

Electric appliances at home and their uses

Machines which use electricity to work or operate, are known as electric appliances. At home there are many electrical appliances. Examples of domestic appliance and their uses are listed in the table below:

These appliances are shown below:

Safety when dealing with electricity

 In as much as electricity can be useful to us, it can also be very dangerous to our lives. All electric appliances need to be handled with care.

Some safety measures when dealing with electricity are:

• Do not touch a non-insulated (bare) electric wire
• Do not touch switches with wet hands
• Do not put your fingers, sticks, pencils or wires in electric sockets
• Do not overload electric circuits.
• Use gloves when handling bare wire
• gloves

For revision question and answers download PDF

Electric energy -upper primary

 

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