electricity - jackson county school districtstatic electricity cannot make ... tvs and light bulbs...
TRANSCRIPT
Electricity Part 1: Static Electricity
Atoms are made up of charged particles.
Atoms are made of 3 subatomic particles: protons, electrons and neutrons.
Introduction: Atoms
Protons
(+) Charge
Neutrons
(-) Charge
Electrons
No Charge
Introduction: Atoms
Protons
(+) Charge
Neutrons
(-) Charge
Electrons
(-) Charge
Normally, the number of protons (+) equals the number of electrons (-) and there is no charge.
If there are more protons (+) than electrons (-) the material will have a positive charge.
If there are less protons (+) than electrons (-) the material will have a negative charge.
Electrons can leave their atoms.
Electrons can easily move, but protons cannot.
Moving Charges
When a material loses its electrons, it develops a (+)
charge
When a material gains electrons, it develops a (-) charge
Electrons can leave their atoms.
Electrons can easily move, but protons cannot.
Moving Charges
When a material loses its electrons, it develops a (+)
charge
When a material gains electrons, it develops a (-) charge
This causes uncharged objects to become (+) and (-) charged
We say the materials have developed a static charge
-
+
Static Charge When two charged objects are placed near
each other, they exert a force on each other.
If objects have different charges, they attract.
If objects have the same charge, they repel.
Objects can be statically charged in 3 ways:
Charging By Friction
Static Charge
When two objects rub together, one object loses electrons and the other gains electrons.
++- -
+- +
- -
+- -
- ++
+negative
Positive
Objects can be statically charged in 3 ways:
Charging By Contact
Static Charge
When a charged object touches a neutral object, the (-) charges move by direct contact.
++-
- - -
- -
- - -
-
negative
Objects can be statically charged in 3 ways:
Charging By Induction
Static Charge
When (-) charges separate without contact and are then pulled away from an object.
- +- +-
-
- -
+- +- -
+- +-
- +
- +-
Positive
Static Charge Charging by contact explains why you get shocked when you touch a metal object.
When you walk across the carpet, you cause
electrons to move from the carpet to the rubber
soles of your shoes.
This creates a build up of excess electrons,
giving your shoes and your body an overall (-)
charge.
When you touch a conductor, like a metal doorknob, the electrons “jump” over to the metal,
giving you a shock!
- -
- - - - -
- -
Lightning Lightning is simply a large scale version of what happens when you get shocked by a doorknob.
Lightning 1 In a cloud, there are (+) and (-) charges.
There are equal numbers of each.
- +
+
+
+-
- -
Lightning 2 Wind and gravity separate the charges, with the
heavier (-) charges going to the bottom.
++ ++
- - - -
Lightning 3
++ ++
Due to induction, the (-) charges in the cloud repel the (-) charges in the ground to move down.
- - - - - - ++++++
- - - -
Lightning 4
++ ++
++++++
Now the ground has a (+) charge. The (+) charges in the ground attract the (-) charges in the cloud.
- - - -
Lightning 5
++ ++
++++++
When the difference is big enough, the (-) charges move from cloud to ground, causing lightning!
Lightning 6
Any Questions?
Electricity Part 2: Current Electricity
1) What Is Current? 2) Electrical Circuits 3) Types of Circuits 4) Current 5) Voltage
Circuit Electricity
In this unit, we will cover:
Static electricity cannot make TVs and light bulbs work.
This is because static electricity only carries a very limited amount of electric charge.
Introduction
To be useful, we need a constant flow of electric charges
This flow is called electric current
Electric current is the flow of electrons through a conductor, such as a wire.
Current
The electrons come from a source like an electric cell, or a battery.
Current
The electrons leave the cell at the negative (-) terminal
Current
The electrons get pushed through the wires along a path
Current
The electrons then return to the cell at the positive (+) terminal
Current
While they flow around the wire, they transfer energy to things
In order for charges to flow, there must be a closed path, or loop.
Electric Circuits
This path is called an electric circuit
Electric current is the flow of electrons through a conductor, such as a wire.
Circuits can either be open or closed:
No continuous path: electrons can’t flow
Open
Continuous path: electrons can flow
Closed
Open and Closed
All circuits have certain basic components:
Electric Circuits
Cell Wires
Switch Device(s)
We draw electrical circuits using simple diagrams.
Drawing Circuits
Circuit Diagram
Circuit Diagrams Circuit diagrams are used to represent the
parts of a circuit in a simple way.
Circuit Symbols
There are 2 major types of simple circuits:
Only 1 path for the current to take.
Series Circuit
Types of Circuits
Each device is wired on a single
path.
There are 2 major types of simple circuits:
Simple to build
Series Circuit
Types of Circuits
If one device stops working, they all do
ADVANTAGES
DISADVANTAGES
There are 2 major types of simple circuits:
More than 1 path for the current to
take.
Parallel Circuit
Types of Circuits
Each device has its own connection
to the cell.
There are 2 major types of simple circuits:
If one device stops working, the others
stay working
Types of Circuits
Complicated to build
DISADVANTAGES
Parallel Circuit ADVANTAGES
Electrons flow through electrical circuits.
Current is the amount of electric charge that flows through a circuit in a given time.
Current
Current is measured in amperes (amps)
Current is measured with a device called an
ammeter
Series
The current changes
depending on the number of cells
The current changes
depending on the number of components
Changing Current
Current In A Series Circuit
In a series circuit, the current is the same every place in the circuit!
4 A ? A
? A
Current In A Parallel Circuit
6 A ? A
? A
? A ? A
In a parallel circuit, the current is the splits up between the different loops
Only 1 path
Series Circuit
Multiple paths
Parallel Circuit
Summary: Current
Current stays same Current splits up
6A 6A
6A 6A 2A 2A 2A
Electrons can only flow if they have energy.
Voltage is a measure of how much energy each electron has in a circuit.
Voltage
Voltage is measured in volts (V)
Voltage is measured with a device called a voltmeter
Parallel
The voltage changes
depending on the number of cells
The voltage changes
depending on the number of components
Changing Voltage
V
V V
Voltage In A Series Circuit
6 V
The 3 bulbs are the same
? V 2 V
V
V
Voltage In Parallel Circuit
6 V
? V
? V
6 V
6 V
Series Circuit Parallel Circuit
Summary: Voltage
Current stays same Current splits up
6A
6A
6A 6A 2A 2A 2A
Voltage splits up Voltage stays same
3V
3V
6V 6V 6V 6V 6V
Any Questions?