1. Energy Resources and Energy Transfer

2. Contents Thermal Energy Transfer Efficiency Energy Resources
Work, Power and Energy
Electromagnetic Forces
Electromagnetic Induction

3. Heat Transfer
Heat is transferred in order to equalise the temperatures of the object and its environment
A cup of coffee will cool down because it is giving out heat energy into the surroundings
This drink (taken out of the fridge) will warm up because it is taking in heat energy from the surroundings

4. Conduction
Atoms in a substance are always vibrating. If the substance gets hotter, the atoms vibrate more. The heat energy is given to the atoms, which makes them move about faster
Every time they collide with another atom, the heat energy is transferred
This is how heat travels through a solid

5. Convection Hot air rises in cold air. Hot water rises in cold water
This is called convection
When hot air rises, colder air has to move in to replace it
Convection cannot happen in solids, as the atoms aren't able to move around

6. Radiation Hot objects radiate heat to their colder surroundings
Black and dull surfaces emit and absorb radiation well
White and shiny surfaces do not emit radiation well and reflect radiation instead of absorbing it

7. Insulation
Air can convect the heat energy away from a house if it is able to move. If the air is trapped in small spaces it can't move so it doesn't convect the heat energy
Fibreglass keeps the air still
Trapped air insulates heat by not allowing it to escape
Double glazing works in this way

8. Power Which boils quicker? Kettle with high power rating
or Kettle with low power rating
Power = how quickly the energy is transferred
(from electrical to heat energy)
High power = Kettle heats up quickly
Low power = Kettle heats up slowly

9. Power P I V The power rating of a light bulb...
Power = how much energy is given
to an appliance per unit of time
Power (Watts) = voltage x current P I V

10. Cost of Electricity 1 unit = 1kWh
 Number of units = power rating x time used

11. Efficiency E T P Power = energy transfer per second
Power = energy transferred/time taken
(W) (J) (sec)
During a movement or change of state (etc.) energy is usually lost as heat energy to the surroundings
The energy inputted is therefore always higher than the useful energy taken out
Efficiency = (useful energy out/energy in) x 100 = % E T P

12. Non-Renewable Fuels All power stations generate electricity:
- Fuel is used to produce heat energy
- The heat energy heats water and turns it into steam
- The steam is pushed at high pressure along pipes to the turbines
- The steam makes the turbines spin, turning a generator which then produces electricity
- The electricity is then supplied to houses, factories and schools via the national grid
Non-renewable (fossil) fuels are oil, gas and coal

13. Nuclear Fuels Uranium is the fuel used in many nuclear power stations
Uranium is not burnt like coal or gas but undergoes nuclear fission
Atoms of uranium are split up which releases large amounts of energy
Nuclear fission produces harmful radiation so people are sceptical
Waste from these reactions is also radioactive
Accidents are serious but very rare

14. Electromagnetic Forces
A current (I) has a magnetic field (B) around it
A wire has a circular magnetic field around it
If the current changes direction, so does the field

15. Electromagnetic Forces
Magnets attract magnetic materials using a magnetic field
The magnetic field surrounds the magnet, and gets weaker as the distance from the magnet increases
Magnets should be called permanent magnets
 the magnetism is always there
Electricity makes a magnet much stronger
This can be turned on and off

16. Electromagnetic Forces
Magnets pick up paper clips etc.
Electromagnets pick up cars etc.
strong
weak

17. Electromagnetic Forces
The magnetic field around a coil electromagnet can be increased by:
- Increasing the current flowing through the wire
- Adding loops on the coil (loops are long lengths of wire)
- Placing an iron or steel core inside the coil
Basic electromagnet

18. Electromagnetic Forces
The Motor Effect:
- When two magnets are placed close to each other, they the fields affect each other produce a force
If a wire carrying a current is placed inside this magnetic field, a force is produced. This is called the motor effect
The direction of the force will depend on the direction of the magnetic field and the direction of the current in the field

19. Electromagnetic Forces
Fleming’s Left Hand Rule:
- When creating a force, use Fleming’s LH Rule to determine in which way the motor will spin -

20. Electromagnetic Forces
We can increase the force produced by:
- increasing the current
- increasing the number of coils
- increasing the magnetic field strength (stronger magnet)

21. Electromagnetic Induction
When a magnet is moved into a coil, an electrical current is induced
When the magnet stops,
the induced current stops
When the magnet reverses, the electrical current reverses

22. Electromagnetic Induction
Increase the voltage? … 3 ways…
Stronger magnet
2. Speed of magnet
3. Number of coils

23. Transformers

24. Transformers
4 coils produce 10V
8 coils produce 20V

25. Transformers
Power stations step-up the voltage to reduce energy losses
(but v high voltage)
Pylons to houses step-down the voltage to
reduce risk of electrocution

26. Summary
Thermal energy is transferred by conduction, convection and radiation
Efficiency % = (useful output/total input) x 100
Fossil fuels are widely used energy resources but these are non-renewable
E = PxT, P = V x I, units = power (kW) x time (hr)
Electromagnetic forces are used to create movement
Movement is used to create voltage using electromagnetic induction