UNIT 8: ELECTRICITY AND MAGNETISM

WHAT IS ELECTRICITY?

The electricity is a kind of energy. It is produced by the movement of charges particles. All objects around us have electrical charges. These charges can be positive or negative.

An electrical current is the flow of electrical charges through materials. This current can produce different effects, such as heat, light, sound, magnetism, movement and chemical effects.

ELECTRICAL CHARGES

Everything around us is electrically charged, including people. Electrical charges can be positive or negative.

Objects usually have the same number of positive and negative charges. This means they are electrically neutral. However, negative charges can  move form one object to another when objects come into contact or are rubbed against each other.

• An object that loses negative charges becomes positively charged.
• An object that gains negative charges becomes negatively charged.

Electrically charged objects can interact in two different ways:

• Objects with the same charge repel.
• Objects with opposite charges attract.

ELECTRIC CURRENT

Electric current is the flow of electrical charges through materials. However, not all material allow electrical charges to flow the same way:

• INSULATORS: electric current doesn't flow through them. For example: plastic, wood, glass...
• CONDUCTORS: electric current  flows easily through them. For example: metals

ELECTRIC CIRCUITS

An electric circuit is a closed path through which electric current flows. It is made of connected components:

• GENERATOR: this provides the electricity. It has a positive terminal and negative terminal. A battery is a generator.
• CABLES: these transport the electricity from the generator to the other components of the circuit.
• SWITCH: this controls the flow of electricity by closing or opening the circuit.
• DEVICES: these transform the electricity into another form of energy, for example, light in light bulbs, heat in radiators or movement in motors.

CIRCUIT DIAGRAMS

ELECTRICAL SAFETY TIPS

• Never use electrical devices in the bath or shower.
• Never plug-in a device when your hands are wet.
• Never open a device or try to repair it without unplugging it first.
• Never clean a device with a wet cloth without unplugging it first.

MAGNETS AND MAGNETISM

Magnets are objects made of materials that have the porperty of attracting iron and some other metals. This property is called magnetism.

There are two types of magnets depending on the origin of the magnetism.
- Natural magnets. These are made of materials, suchs as magnetite, which have natural magnetism.
-Man-made magnets. These are made of materials, such as steel, which acquire magnetism when they come into contact with other magnets.

MAGNETIC POLES

The magnetic properties of a magnet are strongest at the ends, which are called poles. These ends of the magnet are known as the north pole (N) and south pole (S). All magnets have 2 poles (north and south), there is no such thing as a magnet with only one pole.

FORCE BETWEEN MAGNETS

• Two magnets facing each other with different poles attract each other.
• Two magnets facing each other with the same poles repel each other.