FORM 2 CHAPTER 7 ELECTRICITY AND MAGNETISM

CHAPTER 7:

Electricity and magnetism

7.1 ELECTRICITY

• Energy is defined as the ability to
do work.

• It is measured in joules (J).

Daily activities that use energy

People use energy Car need energy Plants need energy
to run, walk and from fuel to move from the Sun to
continue living
play.

HEAT

SOUND LIGHT

ENERGY

ELECTRICAL KINETIC

CHEMICAL POTENTIAL NUCLEAR
ENERGY

KINETIC ENERGY.

• Kinetic energy is energy possessed by a
moving object.

• The kinetic energy of an object increases
when it moves faster.

• Examples:

• A flying bird
• A moving car

POTENTIAL ENERGY

i) Gravitational potential energy
• the energy stored in an object due to its

position. example: Coconut on tree
ii) Elastic potential energy
• the energy stored in an object due to its

condition (compressed / stretched).
• examples: stretched spring, stretched

rubber band.

HEAT ENERGY

• Stored in hot object. Examples Sun,
fire, and boiling water.

• The hotter the object, the higher the
heat energy it gives out.

• The Sun is the main sources of heat
energy.

LIGHT ENERGY

• Energy produced by an object that emits
light.

• Examples Lamp, fire, lightning, bulb, and
candle.

• Enable us to see.

CHEMICAL ENERGY

CHEMICAL ENERGY
• Stored in chemical substances such as
 fuel
 food
 electrochemical cell (Batteries)
 candle

SOUND ENERGY

• Produced by a vibrating object.
• Sound can transferred by gases, liquid

and solid.
• Sound cannot travel in a vacuum.

ELECTRICAL ENERGY

• Produced by the electric charges that
flow.

• Sources of electrical energy are
 dynamos
 Batteries
 solar panel/cell
 generator.

NUCLEAR ENERGY

• Obtained from elements such as
plutonium and uranium (mineral).

• Stored in nucleus of atom by reaction of
fission and fusion.

Sources of energy

The Sun geothermal wind

Wave Fossil fuel Biomass

Water Radioactive
substance

Sources of energy

• There are various sources of energy on
Earth such as:
• fossil fuel (petroleum, natural gas and
coal)
• biomass fuels (from plant and animal)
• Radioactive substances(Plutonium and
uranium are used in nuclear power
station to produce nuclear energy)

• Wind (Caused by winds blowing on the
surface of the sea)

• Water in mountain areas (Changes
potential energy to kinetic energy to
generate electrical energy)

• Waves
• Geothermal (heat from inside the Earth)
• The Sun (and primary and main source of

energy).

Geothermal

GEOTHERMAL

• Geothermal energy uses heat energy from the
Earth’s inner core.

• Geothermal power stations are usually built
on the top of the geysers and hot springs.

• The escaping steam from these places has
high pressure which can rotate turbines and
generators to generate electrical energy.

Geyser

Wind

• Strong wind turns the blades of large wind
mills and wind turbines.

• The blades connected to the generator which
generates electrical energy whenever the
wind causes the blade to spin.

• Wind energy  kinetic energy  electrical
energy

Wind

Biomass

• Biomass energy obtained from plant residue
and waste material from animal.

• Animal waste, oil palm residue, coconut husks,
are put into a digester and left to decompose

• Biomass fuels such as alcohol, methane and
biogas are produced.

Biomass

The principle of energy
conservation

• Energy cannot be created or destroyed
• Energy can changed from one form to

another.

Energy change

• Energy can changes from one form
into another.

• We use a machine to change one
form of energy into another form that
is needed to do certain work.

• A machine that can change energy
from one form into another is called
an energy converter.

Examples:

• Moving car (chemical energy  kinetic energy)
• A radio (electrical energy  sound energy)
• Electric kettle (electric energy  heat energy)
• Alarm clock (potential energy  kinetic energy -

 sound energy)
• A falling coconut (potential energy  kinetic

energy)

A simple pendulum

• When a metal bob is lifted to position P, it possesses
only potential energy.

• When it swings towards position Q after being released,
it loses potential energy and gain kinetic energy.

• Its kinetic energy is maximum at position Q.
• It loses kinetic energy and gain potential energy as it

swings towards position S.

The marble rolls up : kinetic potential
The marble rolls down: potential  kinetic

Maximum potential energy

Kinetic and potential

Maximum kinetic energy

Renewable and non-renewable energy

• Renewable energy sources are energy
sources that can be replaced when they
have been used. This means that the
supply of these energy sources will not
be used up.

• Non renewable energy sources are
energy sources that cannot be replaced
and will finally be used up.

Renewable energy sources

• Wind
• Geothermal
• Sun
• Waves
• Biomass
• Water

Non Renewable energy sources

• Fossil fuels
• Radioactive metals

• They take so long to form and therefore
cannot be replaced.

Energy Advantages Disadvantages
sources
Solar • Unlimited supply • Dependent on weather
• Does not cause • High cost of construction
Hydroelectric
pollution
Wind
• Does not cause • High cost of construction

pollution • Upset the balance of

• Water always available nature

• Unlimited supply • Dependent on wind
• Does not cause
speed and direction
pollution • Cannot produce a lot of

electrical energy

Biomass • Removes waste • Requires a large amount

organic matter of biomass
• Low cost • Requires a large area to

work in

Energy Advantages Disadvantages
sources • Causes air pollution
Fossil fuels • Easy to burn
• Natural gas sets • Risk of accidents
Nuclear • High cost of
free a lot of
energy construction
• Little radioactive
element needed
to supply large
amount of energy

Some ways we can use energy efficiently

• Develop more efficient engines of motor
vehicles and machines.

• Switch off electrical appliances when not
in use.

• Use fluorescent lamps which are more
energy efficient instead of filament lamp.

ELECTROSTATIC CHARGES

There are static (not moving) charges in any objects.

2 types of static electrical
charges

Positive charge Negative charge
(+) (-)

proton electron





How can static electrical charges be
produced?

• Static electrical charges are produced
when two objects (insulator) are rubbed
together.

Characteristics of static electric charges

• Like (same) charges repel.
• Unlike (different) charges attract.

Type of charge produced

+ -
Glass
Cellulose acetate Silk cloth
Silk cloth
Rubber (balloon) Silk cloth, woolen cloth
Woollen cloth
Hard rubber
Fur
Nylon

Rubber (balloon),
polythene
Balloon, ebonite,
polythene

Observation

Material Observation

Bits of paper Attracted towards the plastic ruler

Water stream Attracted towards the plastic ruler

Electroscope The gold leaf diverged

An Electroscope is used to detect
static electrical charges



Static electrical charges

Repel

Dry hair

• Dry hair stand when it is vigorously combed on a dry hair.
• When the hair is combed, friction between the hair and the

comb produces static electrical charges.
• As the hair has like charges, the strands of hair repel one

another and stand.

Lightning

• Produced by a discharge of electrical charges from one cloud
to another or between a cloud and the Earth.

• Negative static electrical charges build up on the clouds
during a storm as strong wind rubs against water particles in
the clouds.

• The negative charges leap to the ground or another cloud
causing lightning.

Earthing

• Send the excessive (berlebihan) electron in a
charged object into earth or vice versa.

• The object is back to neutral.

Lightning Conductor

• A lightning
conductor is a long
thin piece of metal on
top of a building that
attracts lightning (a
lots of electons) and
allows it to reach the
ground safely.

Aeroplane

• An aeroplane flying through the air build up static
electrical charges on its body due to friction with the air.

• When the aeroplane lands, its special conductive tyres
are able to conduct the electrical charges to the ground.

To observe the evidence of the flow of
electric current

• Van de Graaff Generator
Galvanometer

Van de Graff generator.

Scenario

• https://www.youtube.com/watch?v=RSwTXNy
RYcQ

Explanation

https://www.youtube.com/watch?v=laDmuQFm
K3Y&t=1s