Electricity is the flow of electric charge. Electricity is generated by the movement of electrons, which are negatively charged, from one atom to another. Electricity can produce light, heat, motion, and sound. It is transmitted through conductors such as wires and flows in closed loops called circuits. The three main components of an electrical circuit are a power source that supplies voltage, electrical conductors that allow current to flow, and loads that consume energy such as light bulbs. Voltage, current, and resistance are related by Ohm's Law. Circuits can be connected in series or parallel configurations.
2. Lets Review
Atoms have 3 subatomic
particles Charged Atom (atom with a
Protons = positive positive or negative charge)
Electrons = negative Object must gain or lose
electrons
Neutrons = neutral ONLY THE ELECTRONS
MOVE
Neutral Atom Measured in Coulombs
Normal state
# Protons = # Electrons
3. Charge & Force
Attraction
Opposites
Forces pull together + -
Attract
Repulsion
Forces push apart + +
Rules of Charge
Like charges repel (+/+ or -/-)
Opposite charges attract (+/-)
4. Electricity
Definition: Electricity is the energy associated with
charged particles as they move from place to place
The type of material determines how charges move
through them
Conductors
Materials that allow electric charges to move easily
Metals
Insulators
Materials that do NOT allow electrons to flow freely
Rubber, plastic
5. Forms of Electricity
Static
Due to build up of charges in or on an
object
Current
The flow of electrons in a circuit
6. Static Electricity
Static electricity is electricity AT REST
Occurs between 2 objects that become
oppositely charged
Objects involved have unequal electric
charges
Examples
Clothes sticking together in the dryer (if no
dryer sheet is used)
Hair standing up after being brushed (on days
with low humidity)
7. Lightning
Large discharge of static electricity
(electrons transferred from a cloud to the
Earth)
Friction from movement of water drops in a
cloud build up positive and negative charges
Bolts can deliver 100 million volts
Safest place to be in a lightning storm is
inside
Lightning rods are grounded to Earth to
distribute the charge
8. Electric Circuit
An electric circuit is a path for the
electrons to flow
Flowing Electrons = current
Electricity can only flow through a CLOSED
circuit (not an open one)
Hi-Lite
This!
9. Voltage (Potential Difference)
The PUSH that makes electrons flow
(electrons have potential to flow but wont
on their own)
A difference between energy levels is
needed for flow
Electrons flow in a circuit when there is an energy
difference from one end of the energy source to
the other end of the energy source (like a battery)
Units = VOLTS (V)
Symbol = V (capital)
Measured with a Voltmeter
10. Electric Current
The FLOW of electric charges in a circuit
Units = Amperes (amps)
Symbol = I
Speed of Current is affected by
Type, length, & thickness of wire
Voltage
When Voltage , Current
11. 2 Types of Electric Current
Direct Current (DC)
Electron flow is always in the same direction
Ex: Batteries
Alternating Current (AC)
Electrons reverse the direction of flow 60
times per second
Ex: Electricity in the Home
12. Resistance
Opposition to the flow of electrons
Unit = Ohm (立)
Symbol = R
Highest resistance in:
Poor conductors
Thin wires
Long wires
13. Ohms Law
Relates Electric Current, Voltage, & Resistance
V=IxR
Voltage Current Resistance
(volts, V) (amps) (ohms, 立)
14. Ohms Law Example
Calculate the voltage across a 3立 resistor if
a 0.5 amp current is flowing through it.
V=IxR
15. Ohms Law Example
Calculate the voltage across a 3立 resistor if
a 0.5 amp current is flowing through it.
V=IxR
V=?
R=3立
I = 0.5 amp
16. Ohms Law Example
Calculate the voltage across a 3立 resistor if
a 0.5 amp current is flowing through it.
V=IxR
V=? V = (0.5 amp)*(3 立 )
R=3立
I = 0.5 amp
17. Ohms Law Example
Calculate the voltage across a 3立 resistor if
a 0.5 amp current is flowing through it.
V=IxR
V=? V = (0.5 amp)*(3 立 )
R=3立
I = 0.5 amp V = 1.5 v
18. Ohms Law Example 2
A radio with a resistance of 240 立 is
plugged into a 120 v outlet. What is the
current flowing through the outlet?
V=IxR
19. Ohms Law Example 2
A radio with a resistance of 240 立 is
plugged into a 120 v outlet. What is the
current flowing through the outlet?
V=IxR
V = 120 v
I=?
R = 240 立
20. Ohms Law Example 2
A radio with a resistance of 240 立 is
plugged into a 120 v outlet. What is the
current flowing through the outlet?
V=IxR
V = 120 v 120 v = I * 240 立
I=?
R = 240 立
21. Ohms Law Example 2
A radio with a resistance of 240 立 is
plugged into a 120 v outlet. What is the
current flowing through the outlet?
V=IxR
V = 120 v 120 v = I * 240 立
I=?
R = 240 立 I = 120v / 240 立
22. Ohms Law Example 2
A radio with a resistance of 240 立 is
plugged into a 120 v outlet. What is the
current flowing through the outlet?
V=IxR
V = 120 v 120 v = I * 240 立
I=? I = 0.5 amp
R = 240 立 I = 120v / 240 立
23. Power
RATE at which energy is flowing
The measure of the RATE at which
electricity does work or provides energy
Symbol = P
Units = Watts (W)
P=IxV
24. Power Example
If a CD player uses 4.5v with 0.2 amp
current, how much power does it use?
P=IxV
25. Power Example
If a CD player uses 4.5v with 0.2 amp
current, how much power does it use?
P=IxV
P= ?
I = 0.2 amp
V= 4.5 v
26. Power Example
If a CD player uses 4.5v with 0.2 amp
current, how much power does it use?
P=IxV
P= ? P=I*V
I = 0.2 amp
V= 4.5 v
27. Power Example
If a CD player uses 4.5v with 0.2 amp
current, how much power does it use?
P=IxV
P= ? P=I*V
I = 0.2 amp P = (0.2amp)(4.5v)
V= 4.5 v
28. Power Example
If a CD player uses 4.5v with 0.2 amp
current, how much power does it use?
P=IxV
P= ? P=I*V
I = 0.2 amp P = (0.2amp)(4.5v)
V= 4.5 v P = 0.9 W
29. ELECTRICAL Energy
Home use of electric energy is based on
the AMOUNT OF ELECTRICAL POWER
used per hour
Measured in kilowatt hours (1000 Watts
per hour) = kWh
E=Pxt
30. Electrical Energy Example
You use your hairdryer for 20 minutes
everyday. The hairdryer uses 1000 kW.
How many kilowatt-hours does your
hairdryer use in 6 days?
t = 20min/day*6days = 120min = 2hr
E = 1000 kW*2Hr
E = 2000 kWh
31. Circuits
Closed loop made up of at least two
electrical elements
Consists of at least a power source, wire,
and a device that uses electrical energy
(like a light bulb)
32. Symbols for Circuit Diagrams
Positive Side of
Wire
Power Source
Power Source
Negative Side of
Bulb Power Source
Resistance
Switch (open) (closed)
33. Open Circuit
Light will not go on because the wire IS
NOT CONNECTED to the battery on both
sides; current will NOT flow
34. Closed Circuit
Light bulb turns on because the electrical
current CAN now flow through the
complete circuit
35. Series Circuit
All parts of the circuit are connected one after
another in a loop
There is only one path for the electrons to
follow
If one part goes out
The circuit goes from closed to open
Electricity will not flow
All parts go out
The voltage is split through each part of the
circuit
The current is the same throughout the circuit
Example: Christmas Tree Lights
37. Series Circuit Examples
This Light
Bulb is
Burnt Out
The burnt bulb stops the
electron flow to the rest of
the circuit
38. Parallel Circuit
There is more than one path or branch for
the electrons
If a break occurs in one branch, the
electrons can still flow in the other
The voltage is the same throughout each
branch
The current is split through each branch
Example: Household Wiring
40. Parallel Circuit Examples
This
Light
Bulb is
A Burnt
Out
B
Even though Bulb B is burnt
out, the current still goes
through the other circuit and
Bulb A remains lit