SCIENCE FORM 2 CHAPTER 7 (7.1)

CHAPTER 7:

Electricity and magnetism

7.1 ELECTRICITY

• Energy is defined as the ability to do work and is
measured in joules (J).

HEAT

SOUND LIGHT

ENERGY

ELECTRICAL KINETIC

CHEMICAL POTENTIAL

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

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

position. example: Coconut on tree

Elastic potential energy
• the energy stored in an object due to its

condition.
• examples: stretched spring, stretched

rubber band.

HEAT ENERGY

• Stored in hot object. Examples the 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.

• Can detect by eye.

CHEMICAL ENERGY

• Stored in chemical substances such as fuel,
food and electrochemical cell

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
and generator.

NUCLEAR ENERGY

• known as atomic energy.
• Obtained from elements such as

plutonium and uranium.

Sources of energy

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.

ELECTROSTATIC CHARGES

How can static electrical charges be
produced?

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

• Examples of materials that can be charged
easily are glass, ebonite, and plastic such as
acetate and polythene.

Types of static electrical
charges

Positive charge Negative charge
(+) (-)

proton electron

EXAMPLE

Ruler
Ruler

• The transfer of charged particles happens
when two different substances are rubbed.

• An object that loses electrons becomes
positively charged (cloth)

• An object that receive electrons becomes
negatively charged (ruler)

• The charge formed by friction is known as
electrostatic charge.

RULER ATTRACT THE PIECES OF PAPER

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

-ve

+ve

+ve -ve -ve +ve -ve
+ve -ve

+ve +ve
-ve -ve

RULER +ve
(-VE CHARGE) -ve

PIECES OF PAPER
(NEUTRAL)

EXAMPLES OF ELECTROSTATIC

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.