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
What is it?
electric eel

3. Electric Charge and Static Electricity
All matter is composed of very small particles called
Atoms are made up of __________, _________, and ________

4. Electric Charge and Static Electricity
All matter is composed of very small particles called
Atoms are made up of protons, neutrons, and
atoms
electrons

5. Charges and their forces
Two types of charges
Positive and negative
Atoms become charged by gaining or losing electrons
Law of electric charge
Like charges …
repel one another
Opposite charges …
attract one another
(electrostatic attraction) + - + +

6. Electric Force electric force
The force between two charged objects is called the
The strength of the force is determined by two factors:
Size of the charge
Distance between the two charges
electric force

7. Trivia
Who was the first person to realize that lightning is a huge electric discharge?
Ben Franklin

8. Atoms are normally neutral…so how do they become charged?
Friction
Rubbing two objects together
Conduction
Electrons are transferred from one object to the next by direct contact
Induction
Uncharged object charges are rearranged without direct contact with charged object

9. Moving Charges Conductors Insulators
Material in which charges can move easily
Metal (copper, silver, aluminum, etc)
Water (with electrolytes)
Insulators
Materials in which charges cannot move easily
Plastics, rubber, glass, wood, etc…

10. 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

12. 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

13. 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
Human body

15. 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

16. 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

18. 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

19. 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

20. 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

21. Electric fields

22. Electric fields

23. Electric fields

25. Electromagnetic Induction
the production of voltage across a conductor moving through a magnetic field.
It underlies the operation of generators, all electric motors, transformers, induction motors, synchronous motors, solenoids, and most other electrical machines.
Discovered by Michael Faraday
The magnetic field and wire must move perpendicular to each other.
Produces alternating current (AC)

26. Electromagnetic Induction
Lenz's law states,
An induced current is always opposite to the motion causing it

27. Transistors
Semiconductors are 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.

28. Transistors
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.
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. 28

29. 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.

30. Questions

31. Quick Quiz If two charges repel each other, the two charges must be
A. the same B. opposite
A device that can convert chemical energy to electrical energy is a
A. generator B. Cell C. Electric motor
A device that can convert mechanical energy to electrical energy is a
A device that can convert electrical energy to mechanical energy is a
generator B. Cell C. Electric motor
Which type of current flows in only one direction?
Which type of current flows in two directions (back and forwards)
What component of a circuit can amplify an output?
What is the 4th state of matter?
A poor conductor of electricity is also referred to as a _______________.