Energy transfer(chapter 16

1. Energy transfers
Chapter 16
Physics

2. Energy transfers and transformations
We are living at this moment due to the energy
transfers in our body.
As energy is transferred, it is transformed (changed).
Chemical energy in the food is transformed to
movement (kinetic) energy when you raise your hand.
Chemical energy is also transformed into heat energy
to keep you warm.

3. How energy use has increased?
Long ago needed enough stored chemical energy to
people move around and find food.
If they could not find enough food and store it as
chemical energy for later use, they simply starved to
death.
In time people came to live together in groups and
developed machines to make their life easier.

5. Energy transfer diagrams
Energy transformations can be shown by energy
transfer diagrams.
There are 3 parts to an energy transfer diagram:
1) An arrow showing the energy input.
2) A box showing an energy converter or transducer.
3) Arrows showing energy output.

6. Examples of energy transfer diagrams
Stored chemical
energy
Catapult Kinetic energy
Strain energy
Light and heat
energy
Bunsen burner
a) Releasing a catapult
b) Burning gas in a Bunsen burner

7. Light energy
Balloon strain energy
Kinetic energy
Chemical energyCamera
c) Blowing up a balloon
d) Taking a photograph

8. Sankey diagrams
A second kind of diagram that shows energy changes.
It shows arrows of different widths.
The width of the arrow represents the amount of
energy.
The unit of energy and work is the Joule (J).
A thousand Joule (1000 J) = 1 kJ (kilojoule)

10. Plants and energy
- When a seed germinates, the tip of
the root pops out. (Energy stored
inside the seed is used)
- Stored energy is also used by the
growing shoot.
- The shoot grows up through the soil
and uses energy from the seed as it
sends out leaves.

11. - Some of the light energy falling on the leaves is trapped.
- It is converted into chemical energy as the plant makes
food (Photosynthesis).
- The chemical energy stored in plants is transferred to a
herbivorous animal when it eats it.
- The herbivorous animal then has a store of chemical
energy, which it uses to keep itself alive and to move
about.
- Carnivorous animals feed on herbivorous animals and
take in stored chemical energy.

12. Energy and ourselves
What happens when the fat drops
through the grill?

13. - If you do not take care while barbecuing the meat will
catch fire.
- The meat and fat burn because they contain chemical
energy (all food do).
- If you look at food packets, you will find an information
box. It tells you about the ingredients used and nutrients
present.
- Units used to measure energy in food is J and kJ.
- Energy in food is released through respiration process.

14. 1 J = 0.24 calorie

15. Generating electricity
- Electrical energy is a very
useful form of energy
because it is easy to
generate and transport.
- Michael Faraday (1791 – 1867),
an English physicist,
discovered could be made to
flow in a wire if the wire
was made to move through
a magnetic field.

16. - A bicycle dynamo is an electrical device which can be
located in the hub of a wheel (hub dynamo)
- The dynamo can be also clamped onto a bicycle frame
close to a tyre (bottle or sidewall dynamo)

17. Inside a bottle or sidewall dynamo
When the dynamo wheel is in contact with the tyre it rotates as the
bicycle wheel turns, the magnet turns and its field sweeps through the
tyres generating electricity which lights up the lamp.

18. Power station generator

19. - Inside a power station, there is a generator consisting of
a huge electromagnet surrounded by coils of wire.
- The electromagnet is attached to turbine blades.
- When the turbine is made to spin the electromagnet spins
producing an electric current in the coils
- In about 2/3 of the world’s power stations, water is
heated to make steam (in a boiler)

20. Electrical energy
(produced)
Heat energy
(Heats the water)
Kinetic energy
(Water to gas)
Chemical energy
(Coal)
Kinetic energy
(gas moves turbine)
Energy transfers in a power station
Burn it

21. Conservation of energy