What is energy?
Energy is the capacity of an
object or body to transform
an energy source into work.
The quantity of energy is
the equivalent of the quantity
Units of energy
• The international System (IS)
measures energy in joules (J) and
1000 J = 1 KJ
• Heat energy is often measured in units
called calories (cal) and Kilocalories
1 cal = 4,18 J
Years ago, muscle energy was the main source of energy, but we
have invented different mechanisms and machines that have
improved our quality of life.
★Bicycles need our muscle energy when we move the pedals.
★Kitchen appliances need electricity to work, as televisions and
W is work,
t is time,
The power of a machine is the quantity of work it
can do per unit of time. Power is expressed in the
Transformation of energy
It’s when we transform an
initial form of energy into
other forms of energy.
Examples: Chemical to
electrical energy, luminous
to electrical energy...
Energy sources are natural resources that provide
different forms of energy. This energy is transformed
for specific uses. They are classified into: