1. Introduction to Electricity

3. Electric Charge and Static Electricity
Law of electric charges
Electric Force
like charges repel and opposite charges attract
force of attraction or repulsion on a charged particle

5. Electric Field
Charge it
space around charged object in which another charged object experiences electric force
objects become positively charged when it loses electrons
negatively charged when gains electrons

6. Friction
Conduction
happens when electrons are “wiped” from one object onto another
electrons move from one object to another by direct contact

7. Induction
charges in an uncharged metal object are rearranged without direct contact with a charged object

9. Conservation of Charge
Detecting Charge
when an object is charged, no charges are created or destroyed
electrons simply move from one atom to another
Electroscope – uncharged = metal leaves hang down; charged = metal leaves repel

11. Electrical Conductor
Electrical Insulator
material in which charged can move freely
most metals, salt solution, graphite
material in which charges cannot move freely
plastic, rubber, glass, wood, air

12. Static Electricity
Electric Discharge
electric charge at rest
produced by friction or induction
“static” = not moving
release of electricity stored in a source

14. Electric Current and Electrical Energy
energy of electric charges
rate at which charges pass through a given point
measured in amperes (A); in equations the symbol is I

15. Commanding Electrons to Move This electric field is created so quickly that all electrons start moving through the wire at the same instant. Think of the electric field as a command to the electrons to charge ahead.

16. Two Kinds of Currents:
AC – Alternating Current
DC – Direct Current
charges continually shift from flowing in one direction to flowing in the reverse
charges always flow in same direction

18. Voltage
potential difference between two points
measured in volts (V)
amount of energy released as a charge moves between two points in the path of a current
higher voltage = more energy released

19. Resistance
opposition presented to the current by a material or device
expressed in ohms (Ω)
“electrical friction”
higher resistance = lower the current
depends on object’s material, thickness, length, and temperature

20. Resistance and Temperature In general, the resistance of metals increases as temperature rises.

21. Superconductor
Cells
Electrolytes
Electrodes
material with almost zero resistance when cooled
change chemical or radiant energy into electrical energy
batteries are one or more cells
allow charges to flow
part of cell through which charges enter or exit

23. Wet Cell
Dry Cell
Thermocouple
liquid electrolytes
ex. car battery – sulfuric acid
electrolytes are solid or paste-like
converts thermal energy into electrical energy

24. Photocell
converts light energy into electrical energy
ex. solar panel

25. Electrical Calculations
named after George Ohm, 1826
determined how resistance and current affect voltage
increasing voltage increases current
increasing resistance decreases current
V = I x R or I = V/R
V – voltage, I – current/amps, R – resistance
Ohm’s Law

28. rate at which electrical energy is converted into other forms of energy
power = voltage x current P = V x I
measured in watts (W) or kilowatts (kW)
power x time
E = P x t
Electric Power
Electrical Energy

30. Electrical Circuits Electrical Circuit
complete path through which a charge can flow
three parts: energy source, wires, a load (light bulb, radio)
sometimes also includes a switch

32. Open Circuit
Closed Circuit
circuit is broken; electricity will not flow
“turned off”
circuit is complete and electricity will flow
“turned on”

33. Series Circuit
charge has only one path through which it can flow
if one element stop working, none of the elements can work

34. Parallel Circuit
two or more paths through which charges can flow
if one element stops functioning, the rest still operate

35. Fuse
Circuit Breaker
prevents current overload in a circuit
“blowing a fuse” is when a wire in the center of the fuse melts
switch that opens when current is too high

36. Grounding
transfer of excess charge through a conductor to Earth