1. Topic 4: Energy and Electricity

2. Types of Energy
Electrical Energy: the energy contained in the flow of electrons
Heat/Thermal Energy: the energy of a difference in temperature
Motion/Kinetic Energy: the energy of a moving object
Light Energy: the energy contained in light
Chemical Energy: the energy which holds molecules together

3. Electricity and Heat

4. Electricity and Heat
Electrical devices which generate heat typically use an element which has a high resistance. The element heats up as a result of the current flowing through it.
Element

5. Heat and Electricity
Heat can also be harnessed to create electricity through a device called a thermocouple.
Thermocouples use the fact that different metals conduct heat and electricity better than others.
The difference causes a flow of electrons when the two metals are connected at nodes.

6. Heat and Electricity continued
Thermocouples only produce a very small current, which makes them good for sensing temperature, but not for powering electronic devices.
They are much more durable (no glass) and versatile (able to read much larger temperature differences) than traditional mercury thermometers.

7. Heat to Electricity Continued
You can get more current from thermocouples by hooking them in series, like getting more current from multiple batteries. This arrangement of thermocouples in series is called a Thermopile
Temperature 1
Temperature 2

8. Heat to Electricity Continued
Thermopiles can be used in devices called Thermoelectric Generators which burn fuel over the thermopile to create a temperature difference.
Thermoelectric generators create electricity without any moving parts. This makes them very reliable
Ideal for remote locations and for emergency systems.
- TEG

9. Electricity and Motion

10. Electricity and Motion
Examples of electricity causing motion are electric motors and electric generators
Examples of motion causing electricity are barbeque lighter igniters and piezoelectric crystals
Piezo comes from the Greek “pressure or push”
Analog watches use quartz (a piezoelectric crystal) to maintain time.

11. Electricity and Motion
Piezoelectric crystals are unique in that:
When a current is passed through the crystal, it vibrates
Analog watches use this to keep time
When the crystal is struck or squeezed, it produces a voltage
Barbeque lighters use this to ignite the lighter fluid

12. Electricity and Light

13. Electricity to Light
Incandescent bulbs – uses a filament which is similar to an element in a toaster to produce light.
Advantages: Warm, consistent light. Bulb is dimmable using a variable resistor. Bulbs come in all shapes and sizes. Inexpensive
Disadvantages: Filaments do not last very long. A lot of heat is produced – not very efficient.

14. Electricity to Light
Fluorescent bulbs – uses a tube containing a gas which glows when a current is passed through it.
Advantage: More efficient than incandescent bulbs.
Disadvantages: More expensive than incandescent bulbs. Contain harmful chemicals. Bulb shapes do not fit every application.

15. Electricity to Light
LED (light emitting diode) bulbs – uses a semiconductor to convert electricity directly to light.
Advantages: Much more efficient than both incandescent and fluorescent bulbs. Extremely long life.
Disadvantages: Quite expensive. They only work when connected into a circuit in one direction.

16. Light to Electricity Light to Electricity
Light can be converted to electricity by using photovoltaic (PV) cells.
Photovoltaic cells are made of semiconductors such as silicon which absorb some of the light which strikes them. This causes electrons to be ejected from the silicon atoms.
Individual PV cells don’t create a large amount of current. They need to be connected in series to form Arrays similar to thermocouples and batteries.