1. An Introduction to Electricity

2. Shocking fish tales…. electric eel
Freshwater fish found in Central and South America
Can produce up to 600V of electricity from muscle tissue (that’s 5 times the volts from an electrical outlet)
Electricity is used for stunning prey, self-defense, and communication
electric eel

3. Electrical energy What is an “electrolyte”?
A cell or battery converts chemical energy to electrical energy
Wet cell – electrolyte is contained in a solution
Dry cell – electrolyte is solid or paste-like
What is an “electrolyte”?
An electrolyte is a liquid or gel that contains ions
electrode
electrolyte

4. Potential Energy
GPE
GPE Example

5. Electrical Current
The electricity flows because the chemical reaction causes a change in charge between the two (positive and negative) electrodes
potential difference the electrical force driving the charge through the conductor expressed in volts (V)
(average household batteries are one cell with 1.5V of potential difference)
Current: the rate which a charge passes a given point is expressed in Amperes (A) or amps

6. Electrical Current Consider a waterfall
The height of the fall is like the voltage
The rate at which water is coming over the fall is like current

8. Stun gun vs. electrical outlet
Stun guns generate a high-voltage, low-amperage (3 milliamps) electrical charge. This means that the charge has a lot of pressure behind it, but not that much intensity.
demonstation
a typical household circuit can deliver 15 to 20 amps (15,000 – 20,000 milliamps)
Human body

9. types of electrical current
Two types of electrical current
DC – direct current
Electrical charges always travel in the one direction
Electrical current produced by batteries is DC
AC – alternating current
Electrical charges flow in two directions (forwards and backwards along a wire)
Electrical current produced by electrical generators is AC

11. Questions Two protons will _______ each other Repel
Atoms become charged by gaining or losing…
Electrons
A material in which charges can move easily is a…
Conductor
A material in which charges can’t move easily is an…
Insulator
Electrical charges flow in two directions (forwards and backwards along a wire)
Alternating current

13. Electric fields
An electric field surrounds electrically charged particles
The electric field exerts a force on other electrically charged objects
The concept of an electric field was introduced by Michael Faraday.
It is a force similar to gravity

14. Electric fields
Electric fields can be mapped and illustrated using field lines
Lines are drawn going out from positive particles and going into negative particles
Lines are drawn close together to show where the field is stronger and farther apart to show where the field is weaker
field lines animation 1
field lines animation 2

15. Electric fields

16. Electric fields

17. Electric fields

19. Plasma
a mixture of positive ions and free electrons that is electrically neutral on the whole but that can conduct electricity.
created by very high temperatures when molecules break up into positively charged ions and negatively charged electrons.
Much of the matter in the universe is in stars in the form of plasma
Plasma is considered a fourth state of matter, as fundamental as solid, liquid, and gas.

20. Plasma What are some examples of plasmas?
Amazing Northern Lights Time Lapse
Aurora Australis 1
Aurora Australis 2

21. Transistors
Semiconductors materials in which only high energy electrons can “flow.” As the temperature rises, more electrons are free to move through these materials.
Semiconductors have had a monumental impact on our society. You find semiconductors at the heart of microprocessor chips as well as transistors. Anything that's computerized or uses radio waves depends on semiconductors.
Today, most semiconductor chips and transistors are created with silicon. You may have heard expressions like "Silicon Valley" and the "silicon economy," and that's why -- silicon is the heart of any electronic device.

22. Transistors What type of element is silicon?
Semimetal (metalloid)
Would you expect silicon to be a conductor of electricity or an insulator?
You can change the behavior of silicon and turn it into a conductor by doping it.
In doping, you mix a small amount of an impurity into the silicon crystal. 22

23. Transistors
A diode is the simplest possible semiconductor device. It allows current to flow in one direction but not the other.
A transistor is created by using three layers rather than the two layers used in a diode.
A transistor can act as a switch, amplifier or AC/DC converter.
transistors have almost entirely replaced vacuum tubes that were widely used in early radios, television sets, and computers.
For example, a device that uses batteries often contains a diode that protects the device if you insert the batteries backward. The diode simply blocks any current from leaving the battery if it is reversed -- this protects the sensitive electronics in the device. 23

25. Transistors
How Transistors Work 25

26. Questions