Sains Tahun 3: CHAPTER 4 ELECTRICITY

What is the definition of “electricity”?

Electricity is a form of energy usually carried by wires or produced by batteries used to power machines and computing, communications, lighting, and heating devices.We use electricity every day. Appliances at home such as television, fan, water heater and refrigerator work when electricity flows through them in a complete circuit. An electric current does not flow through an incomplete circuit.

Diagram 1: A Complete Circuit

How Does a Bulb Lights Up Brighter or Dimmer?

A bulb lights up when electricity flows through a complete circuit which consists of a bulb, wires and a battery ( Diagram 1 ). Electricity flows from the positive battery terminal across a complete path toward the negative terminal.

Diagram 2: Bulb Lights Up Brighter

A bulb is brighter when more electricity flows through it. How? By adding one more battery to the circuit ( Diagram 2 ). The number of batteries used affects the brightness of a bulb in a circuit. But another battery further added to the circuit, the bulb will blow because there would be too much energy passing through the circuit.

Diagram 3: Bulb Lights Up Dimmer

A bulb is dimmer when less electricity flows through it. How? By adding another bulb to the original circuit ( Diagram 3 ). This is so because two bulbs sharing the power of one battery.

What Materials Conduct Electricity?

Some materials conduct electricity and some do not. Materials that conduct electricity i.e. allow electricity to flow through them are called conductors. All metals conduct electricity, for examples, silver, copper, gold, steel, tin, aluminium, iron and lead. Examples of objects which conduct electricity are as follows:

iron rod, silver spoon, 20-sen coin, gold ring, needle, paper clip, copper wire, aluminium foil, tin can, scissors, steel wool, iron nails, pencil lead, water and orange juice

Materials that do not conduct electricity i.e. do not allow electricity to flow through them are called non-conductors. Wood, plastic, cloth, rubber and glass are materials that do not conduct electricity. Examples of objects which do not conduct electricity are as follows:

matchstick, plastic comb, crayon, straw, chalk, paper, eraser, wooden ruler, glass, sponge, marbles, plastic spoon, toy, slippers, rubber band, button and cellophane tape

The Switch

A circuit must also contain a switch. A switch is used:

to stop the flow of electricity/current in the circuit by opening it (disconnect or break the circuit)

( Diagram 4 ); or