Transcript Atomic Structure - BDJ Engineering

“What is Electricity?”
Review
Atomic Structure
• What is an Element?
Elements
The simplest form of matter
• What is an Atom?
Atoms
The smallest piece
of an element that
contains all
properties of that
element
• What 3 particles make up atoms?
Components of an Atom
Electrons
Negatively charged
atomic particles
Protons
Positively charged
atomic particles
Neutrons
Uncharged atomic
particles
• What determines the atomic number of an
atom?
• What is the atomic number of Copper
(Cu)?
Atomic Number
The atomic number is
equal to the number of
protons in the nucleus
of an atom.
The atomic number
identifies the element.
How many protons
are in this nucleus?
Periodic Table of Elements
NASA
Which element has 4 protons?
Electrons
For this unit, we mainly care about
electrons in atoms.
Why?
It is important to understand the
“how and why” of the movement of
electrons to understand electricity.
• Draw a representation of a Sulfur atom
(Atomic Number 16).
• Draw a representation of a Helium atom
(Atomic Number 2)
Filling order:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, …
Electron Orbits
Atoms like to have their valence level either
filled (8) or empty(0) of electrons.
How many electrons
are in the valence
level?
6
Sulfur has space to
gain two electrons in
its valence level.
• What is a valence electron?
• How many valence electrons do
conductors have?
• How many valence electrons do insulators
have?
• How about semiconductors?
Conductors and Insulators
Conductors
Insulators
Electrons flow easily
between atoms
Electron flow is difficult
between atoms
1-3 valence electrons in
outer orbit
5-8 valence electrons in
outer orbit
Low Electronegativity
High Electronegativity
Good Conductors:
Silver, Copper, Gold,
Aluminum . . .
Examples: Mica, Glass,
Rubber, Plastic . . .
What is a Multimeter?
An instrument for measuring the
properties of an electrical circuit
Manual vs. Auto Ranging
Where should you set the meter if you
expect a reading around . . .
6 volts
50 millivolts
800 millivolts
800 volts
125 volts
History
Ben Franklin
suggested
that . . .
+
. . .opposite
charges attract
and like charges
repel.
-
History
Ben Franklin
suggested
that . . .
. . .opposite
charges attract
and like charges
repel.
The Law of Charges explains why the electrons continue to
be bonded to the nucleus.
+
+
Electron Flow
An electron from one atom can knock out an
electron from another atom.
Electron Flow
Electricity is created as electrons collide and
transfer from atom to atom.
Play Animation
What Makes Up Electricity?
Let’s compare it to something we
know --- Water!
Water Analogy
Tank
Faucet
Pipe
Tank = Battery
Pipe = Wiring
Faucet = Switch
• What is current?
Current
Current: The flow of electric charge
Tank (Battery)
Faucet (Switch)
Pipe (Wiring)
When the faucet (switch) is off, is there any flow (current)?
NO
When the faucet (switch) is on, is there any flow (current)?
YES
Current in a Circuit
off
on
When the switch is off, there is no current.
When the switch is on, there is current.
• What is voltage?
Voltage
Voltage: The force (pressure) behind
the flow of current
Tank (Battery)
Faucet (Switch)
Pipe (Wiring)
When the faucet (switch) is off, is there any pressure (voltage)?
YES – Pressure (voltage) is pushing against the pipe, tank, and the faucet.
When the faucet (switch) is on, is there any pressure (voltage)?
YES – Pressure (voltage) pushes flow (current) through the system.
Voltage in a Circuit
off
on
The battery provides voltage that will push current
through the bulb when the switch is on.
• What is resistance?
Resistance
Resistance: The opposition to the
flow of current.
Tank (Battery)
Faucet (Switch)
Pipe (Wiring)
What happens to the flow (current) if a rock gets lodged in the pipe?
Flow (current) decreases.
Resistance in a Circuit
off
on
Resistors are components that limit the flow of electricity.
Reducing current causes the bulb to become more dim.
What types of electricity are
there?
Types of Electricity
Static Electricity
The electrical charge an object
develops as a result of having an
unequal number of protons and
electrons.
Current Electricity
The movement of electrons
through a conductor.
Static Electricity
• Uncontrollable
Electricity
• Lightening
• Static Cling
• Wool socks on a carpet
“shocks”
• What are the two types of current
electricity?
• What is the difference between these two?
Current Electricity
Two Types:
Direct Current
(DC)
Alternating Current
(AC)
Direct Current
The electrons flow in the same direction all
the time, from negative to positive.
-
+
Direct Current
Comes from
• Batteries
• Converted from Alternating Current
Used for electronic devices including
• Computers
• iPods
• Cell phones
• Anything that has a “charger”
Alternating Current
The electrical current (movement of
electrons) changes direction.
Alternating Current
Comes from Generators
• Coal burning and nuclear power plants
• Hydroelectric power plants
• Wind and solar generators
Used for
• Motors
• Heaters
• Lights
• Anything that plugs into the wall
What is a Magnet?
An object that is
surrounded by a
magnetic field and has
the property of attracting
iron or steel
Where are Magnets?
Magnets. . .
Generate
electricity
Image courtesy of DOE/NREL
Are in motors
Image courtesy of DOE/NREL
Where are Magnets?
Magnets. . .
Power car
windows & locks
Are used in Magnetic
Resonance Imaging (MRI)
Image courtesy of NASA
• If a large magnet breaks into the small
pieces what will their poles be?
North and South Poles of a Magnet
Magnets have a north and south pole.
• If a magnet is broken into smaller pieces, each
piece will still have a north and south pole.
• Opposite poles attract, like poles repel.
N
N
S
N
N
S
S
S
S
N
• How do compasses work?
The Earth as a Magnet
The Earth is a large magnet.
Compasses work as a result
of the Earth’s magnetic field.
• What is an electromagnet?
Electromagnets
Magnets are created by passing a current
through a wire.
Electromagnets are generally wire wrapped
around an iron core.
Electromagnets are turned on and off when
the current is switched on and off.
• How can you switch the poles of an
electromagnet?
Electromagnets
N
S
Electromagnet ends
change between north
and south depending
on the direction of the
current.
S
N
• What parts make up a motor?
Parts of a Basic DC Motor
Motor: A device used to convert electric energy into
mechanical energy.
Brush
DC Source
Commutator
N
N
Permanent
Magnet
Armature
S
Permanent
Magnet
S
Commutator
Brush
Parts of a Small DC Motor
Brushes
Wire
Connections
Permanent
Magnets
Armature
Commutator
• What is an electric generator?
Electric Generators
Generator: A device used to convert mechanical
energy into electrical energy.
Mechanical motion turns the armature which creates current.
Many DC motors can function as a generator.
N
N
S
S
• Explain the steps by which electricity goes
from the power plant to your home.
From the Power Plant to Your Home
Image courtesy of Sacramento Municipal Utility District
Power plants
generate electricity.
From the Power Plant to Your Home
Step up transformers increase voltage for
transmission across large towers.
Increased voltage increases efficiency.
From the Power Plant to Your Home
Images courtesy of DOE / NREL
Large towers transmit electricity over long
distances.
From the Power Plant to Your Home
Step down transformers reduce voltage
at substations to acceptable levels for the
end user.
From the Power Plant to Your Home
Electricity arrives at your home at a
junction box.
Usage is measured with a meter.
• Briefly explain how Maglev Trains work