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






Brighter and Dimmer
A bulb lights up when electricity flows through a complete circuit which consists of a bulb, wires and a battery. A bulb lights up brighter when more batteries are added into a circuit. A bulb becomes dimmer if more bulbs are added to the same circuit.

How Does a Bulb Lights Up Brighter or Dimmer?

Diagram 1: Bulb Lights Up Brighter

A bulb is brighter when more electricity flows through it. How? By adding one more battery to the circuit (Diagram 1). 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 2: Bulb Lights Up DimmerA bulb is dimmer when less electricity flows through it. How? By adding another bulb to the original circuit (Diagram 2). This is so because two bulbs sharing the power of one battery.

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

A Switch
A switch is used to connect or break a circuit. The circuit is complete when the switch is on. Electricity flows through it to light up the bulb. When the switch is off, the bulb will not light up.

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 3); or

Diagram 3: Switch Off (Open), Bulb No Light

• to allow the flow of electricity/current by closing it (connect the circuit) (Diagram 4).

Diagram 4: Switch On (Closed), Bulb Lights Up

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WORKSHEET


Section A

1. The bulb in a complete circuit becomes ( brighter / dimmer ) if more electricity flows through it.
2. A bulb becomes ( brighter / dimmer ) if more bulbs are connected to it.
3. When a switch is turned on, it ( completes / break ) the circuit.
4. When the switch is ( on / off ), the bulb will not light up.

ANSWER

Section B

Complete the table below.

Objects That Conduct Electricity	Objects That Do Not Conduct Electricity

ANSWER

MAGNETS

What is Magnet?
Magnet is an object consists of iron and steel. Magnets are used in many objects around us.


How Magnets Attract or Repel?
A magnet has two poles namely, north pole (N-pole) and south pole (S-pole). When the N-pole of a magnet is placed near the N-pole of another magnet, the poles will repel or push away each other. The outcome will be the same if the S-pole of a magnet is placed near the S-pole of another magnet. They will only attract or pull each other if the N-pole of the magnet is placed close to the S-pole of another magnet.

Another way of explaining: different poles or unlike poles of two magnets brought near each other, the magnets will attract. When the same poles or like poles of two magnets brought near each other, the magnets will repel.

Picture 1:  Magnet Attract & Repels

Picture 2: Magnectic Field Lines

Handling Magnets The Proper Ways

Magnets can lose their magnetism or strength if we knock them, drop them or heat them.  Thus, magnets must be handled with care to preserve their strength. The strength of the magnets can be preserved by storing the magnets with iron keeper or magnet keeper. Placing keepers at the poles of the magnets can help them last longer.

Magnets Attract some Materials & Objects 

Objects that can be attracted by magnets are called magnetic objects whilst those objects that cannot be attracted by magnets are called non-magnetic objects. Magnetic objects are made of iron or steel. Non-magnetic objects are made of plastic, cloth, wood, glass, rubber and gold.

          Magntic Objects                               Non-Magnetic Objects

Strengths of Magnets

The strength of magnets are different from magnet to magnet. The size of the magnets of the same type and the type of magnet does affect its strength. A strong magnet can attract more objects than a weak magnet.

Uses of Magnets

Magnets are used in many things such as in refrigerator, pencil case, and compass. Do you know how magnets are used in these things?

Refrigerator- Magnetic strip is used to close the door firmly.

Pencil case- Magnetic bar is used to close the pencil case tightly.

Compass- Magnetic needle helps to show directions.

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WORKSHEET

1. Look the diagram above, what happens when these magnets are brought close to each other?


    a) The magnet ( repels / attracts ) the other magnet.

    b) The magnet ( repels / attracts ) the other magnet.

    c) The magnet ( repels / attracts ) the other magnet.

    d) The magnet ( repels / attracts ) the other magnet

 ANSWER

2. Complete the table below.

Objects Attracted to a Magnet	Objects Not Attracted to a Magnet

ANSWER

ANSWERS (MAGNET)

Question 1:
a) repels
b) repels
c) attracts
d) attracts

Question 2:

Objects Attracted to a Magnet	Objects Not Attracted to a Magnet
Nails	Pencil
Pins	Book
Key	Soap