SECTION 1: Definition and forms of energy
What is energy?
What are the main forms of energy?
How do we measure energy?
What is power and how is it measured?
✔ What is energy? What are its main forms?
◦ Energy is the capacity to cause changes. ◦ Changes of position, temperature and electric charge are among the most frequent.
◦ Each type of change defines a distinct form of energy: Mechanical energy causes
changes of position.
Thermal energy causes
changes of temperature.
Electrical energy causes
changes of electrical charge.
✔ How do we measure energy?
◦ Energy can not be directly measured. ◦ In order to measure energy, we need to focus on the change that it causes. Mechanical energy is
measured through velocity
by using the formula
E = (m∙v2) / 2
The units are Joules
(1 J = 1kg at 1m/s)
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Mechanical energy can be
classified into kinetic (motion)
energy, and potential (height)
energy. The latter can be calculated by
the expression: E = m ∙ g ∙ h
SECTION 1: DEFINITION AND FORMS OF ENERGY
IES ATENEA (ALCALÁ DE HENARES)
Thermal energy is measured
through temperature by
using the formula:
E = m∙C∙(Tf ­Ti)
The units are Calories
(1 Cal heats 1ºC 1g of water)
Electrical energy is
measured multiplying the
power of the device by the
time it's on:
Heat was at first considered, not
a form of energy, but a kind of
fluid that was able to flow from
hot to cold objects. Robert Joule
discovered in 1843 that heat is
actually a form of energy. The
unit of energy bears his name
after that. 1 kwh is, for example, the energy
needed to turn on a 100 watt light
bulb during 10 hours. It costs
about 10 c€
E = P∙t
The units are kwh
(1 kwh = 3.600.000 J)
✔ What is power and how do we measure it?
Power is the amount of
energy provided or
consumed per unit of
time.
P = E / t Power is measured in watts, being 1
watt the power of a machine that
provides or consumes 1 joule per 1
second. James Watt was the inventor of the
steam engine .
Power is also measured in
horsepower (HP) in cars. 1
HP = 745,7 watts. Cars
provide usually more than
100 HP
✔ Conservation of energy.
Energy can not be created or destroyed. It
can only be transformed. This can be
expressed by the energy cycle, which
expresses the fact that there is always a
machine that can transform any type of
energy into any other.
TECHNOLOGIES ESO 1
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Thermal
Mechanical
Electrical
SECTION 1: DEFINITION AND FORMS OF ENERGY
IES ATENEA (ALCALÁ DE HENARES)
Vocabulary
Mechanical
Kinetic
Potential
Thermal
Power
Useful expressions
In order to express that something is important
we use “to focus on”
We must focus on protecting the environment by saving energy. –­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­>ACTIVITIES
1. Explain which transformation of energy is performed in the following machines: 2. Match the process with the corresponding form of energy: ◦ Boiling water
◦ Riding a bike
◦ Using a cell phone
◦ Electrical
◦ Thermal
◦ Mechanical
3. Work out the kinetic energy of a 1000 kg car when its velocity is:
1 m/s
2 m/s
3 m/s
4. Figure out how much energy its needed to turn on a 50 w light bulb during 100
hours. 5. True or false: a) Energy can be created out of nothing for free.
b) Heat can be transformed into mechanical energy.
c) Electricity is not a form of energy.
d) Power and energy are the same thing.
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TECHNOLOGIES ESO 1
UNIT 7: ENERGY
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SECTION 1: DEFINITION AND FORMS OF ENERGY
IES ATENEA (ALCALÁ DE HENARES)