Download Static Electricity

Unit D - Electricity
Week 1
STATIC ELECTRICITY
I can…
• Distinguish between static and current
electricity, and identify examples of each
Static electricity
• Static electricity is a stationary electric charge
• What does stationary mean?
• The charge is not flowing like a current
• Ex. Lightning, static electricity on clothing,
“shocking people” by touching them, shock
from your car.
Electrical charge
• Remember that opposites attract which is true
of negative charges
• Most objects have an equal number of
positive and negative charges so they are
considered neutral
• When an object has more of one charge we
say it is charged
• Ex. An object with extra electrons is negatively
charged
Draw this picture in your Notes!
Positive Charge = Protons
Negative Charge = Electrons
Electrical discharge
• Static electricity does not continue to flow, but
it can undergo electrical discharge
• The build up charge on an object can be
attracted to another object and jump to that
object
• We call the spark an electrical discharge
Laws of electrical discharge
• Opposite charges attract each other
• Like charges repel each other
Charge separation
• Charged objects cause a charge separation
when they are brought close to neutral
objects
• For example, a negatively charged balloon,
when brought close to a wall will cause the
negative particles in the wall to be repelled,
and therefore will be attracted to the positive
particles left in the wall.
Review Questions
• What is the difference between a proton and
an electron?
• What does it mean to be “statically charged”?
• How do like charges interact?
• How do unlike charges interact?
• A neutral object contains no charge. Is this
true?
Salt and Pepper Activity
• Complete the Salt and Pepper Activity – This is
due at the end of class.
CURRENT ELECTRICITY
I can…
• Distinguish between static and current
electricity, and identify examples of each
• Identify electrical conductors and insulators,
and compare the resistance of different
materials to electric flow
Introduction
• https://www.youtube.com/watch?v=a3sviTa8
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• Is the charge on the eel a static charge or a
current?
Electrical Current
• Static charges can discharge but they are not
useful for operating electrical devices because
they do not flow continually
• The steady flow or charged particles is called
electrical current
• Electrical current can be used to run electrical
devices as long as 2 things occur
– Need a source of energy
– Circuit must be closed
The necessary parts to a Circuit
•
•
•
•
1) Conductor- wire
2) Energy Source- battery or outlet
3) Load- the thing that uses the electricity
4) Control- often a switch
Conductor
• A conductor allows electricity to move
through it easily
• What are examples of conductors?
• What is the opposite of a conductor? What
are examples of these?
Insulators
• in an insulator the electrons are bound tightly
to the nuclei so they resist movement
Conductors and insulators
• When would you want to use a conductor in a
circuit?
• When would you want to use an insulator in a
circuit?
Conductor and Insulator Sort
• Complete the Notebook Activity on
Conductors and Insulators
• What about wearing a Suit of Armor in a
Lightning Storm?
Superconductors
• Some metals are better conductors than
others because they give less resistance to the
electrons that are flowing
• Superconductors are perfect conductors- they
have no resistance to electron flow
– Extremely low temperatures help reduce
the resistance in the superconductors
– What’s the issue to running a
superconductor at a low temperature?
Circuits
• A circuit is a path that controls the flow of
electricity
• Usually electricity moves through solid wires
but it can move through gases or other fluids
• Open and Closed Circuits
Open and Closed Circuits
• Complete the Smart Notebook Activity with
Open and Closed Circuits
Quick Lab
• With a partner do the following lab– you have 20
minutes
– 1) Using any materials, make one light bulb light up
– 2) Using a battery, one bulb and 1 wire, make the light
bulb light up
– 3) Using any materials, make 2 light bulbs light up
– 4) Make 2 light bulbs light up so that when you
unhook one bulb, the other goes out
– 5) make 2 light bulbs light up so that when you
unhook one bulb, the other stays on
CELLS AND BATTERIES
I Can…
• Investigate and evaluate the use of different
chemicals, chemical concentrations and
designs for electrical storage cells. (explain
functions of parts and diagram)
Electrochemical Cells
• An electrochemical cell is a package of 2 types of
metals and an electrolyte
• One metal has more free for electrons than the
other metal, so when a wire is attached to create a
circuit the electrons get to move from one metal
to the next, which creates a current
• There are 2 ends on a battery,
– Cathode = positive
– Anode = negative
Types of cells
• Cells can power tiny pacemakers, toys, cars or
computers
• There are 2 types of cells
– 1) Dry cells- the electrolyte is a paste
– 2) Wet cells- uses a liquid electrolyte
Dry Cells
• The electrolyte in a dry cell allows ions to flow
which completes the circuit
• An ion is an atom with a charge
• Positive terminal- where electrons travel back
to the cell
• Negative terminal- where electrons travel
from the cell
Dry Cells
• The 2 metals are called electrodes
• One electrode becomes positively charged,
and the other becomes negatively charged.
• ALKALINE (having a basic electrolyte)- are
some of the most common dry cells
• What does alkaline mean again?
Wet cells
• Wet cells often have a liquid such as sulfuric acid as their
electrolyte
• They are usually cheaper and easier to make than dry cells but
are more dangerous
• Vehicles use wet cells that need to be disposed of properly
• There are individual cells that alternate within the battery
• Each cell has a positive and a negative plate
• The terminals in the battery are at the top
Think about it!
• Is it correct to call a car battery a battery?
Wet Cell Batteries
Answer to Think about It!
Primary vs. Rechargeable cells
• Primary cells: cells that can only be used one
time
• Rechargeable cells aka secondary cells- can be
reused, the chemical reaction that occurred
originally is forced to go back so it can be used
again
• Ni-Cd batteries are common secondary cells
(made up of nickel and cadmium)
Battery
• Society today does not use the work battery
correctly
• A battery contains more than one cell
Electrochemistry
• Alessandro Volta made the first practical battery around 1800
by stacking copper and zinc disks with an electrolyte solution
• Other scientists used batteries to split molecules into their
elements electrolysis (ex. Water used as a fuel for rockets
by breaking into oxygen and hydrogen)
• Electrochemistry was begun which is the study of chemical
reactions involving electricity
• Scientists discovered that by putting more than one cell
together they could increase the current and the power of the
battery
• http://www.edumedia-sciences.com/en/media/670electrolytic-conduction
• https://www.youtube.com/watch?v=8oeUE6dlP2A
Electroplating
• Electroplating uses the technology of a battery
in reverse to create a layer of silver or gold on
an object
How to electroplate
• The metal that is to be coated is immersed in
an electrolyte solution with metal bar in it.
• The metal ions bond on the object and
become a solid metal deposited on top of the
less expensive materials
• http://www.youtube.com/watch?v=z7f7dQF2
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CONTROLLING THE FLOW OF
ELECTRICAL CURRENT
I can…
• Draw and troubleshoot circuit diagrams for a
variety of specific purposes.
• Explain how switches and resistors can control
electrical flow, and predict the effects of these
changes on output in a circuit.
A Unique circuit
• Neon signs have neon gas in them, when
electricity is run through them they glow.
• The circuit needs to be complete and needs to
be controlled carefully
Resistors
• Resistance is a measure of how difficult it is
for electrons to flow through a substance
• A resistor uses power (a load can be a resistor)
• Resistance is measured in ohms –symbol Ω
(omega)
• The more resistance a substance has the more
energy it takes from the electrons that pass
through it
Switches and Variable resistors
• Switches allow the control of a circuit by
simply shutting it “on” or “off”
• A variable resistor or a rheostat can adjust the
resistance in an object that the current flows
through
• Ex. Volume control on stereos, dimmer light
switch
ANALYZING AND BUILDING
ELECTRICAL CIRCUITS
I Can…
• Draw and troubleshoot circuit diagrams for a
variety of specific purposes.
• Explain how switches and resistors can control
electrical flow, and predict the effects of these
changes on output in a circuit.
Types of circuits
• The most economical way to design a circuit is
in a loop
• However, we do not always want every part of
the circuit being dependent on the others in
the circuit
• Ex. Would it be convenient for a plug-in to
only work if the light switch was on?
Other types of Circuits
• Series Circuits
• Parallel Circuits
• http://www.edumediasciences.com/en/media/2
29-series-and-parallelcircuits
Series circuit
• In a series circuit there is only one pathway for
the current
• If the pathway is interrupted the circuit cannot
function
• Problem: adding more things increases the
total resistance  light bulb will get dimmer
as we add more
Parallel circuit
• Parallel circuits have a current path for each
section of the current
• A break in one pathway does not affect the
others
• Adding more pathways decreases the total
resistance
Parallel vs Series
• Complete the Smart Notebook Activity using
Series and Parallel Circuits
• http://cashmancuneo.net/flash/parallel.swf
Circuit drawing
• We use special (easy to draw) symbols to represent
parts in a diagram
• An electrical diagram is called a schematic
• 4 parts of a circuit
– Source
– Conductor
– Switch or control
– Load
Lets draw parts for our Schematic
Diagram
Tips for drawing schematics
• Conductors are always drawn in straight lines
with 90 degree angles
• The symbols are made the same size
• Conductor lines are not allowed to cross
Example
Complete the Circuit Assignment in
your notes.
1. A closed circuit with a two-cell battery, a bulb
and a switch.
2. An open circuit with a three-cell battery, a bulb
and a switch.
3. A closed circuit with a three-cell battery, two
bulbs, a switch and an voltmeter
4. A circuit with a two-cell battery and two bulbs
that can are controlled by one switch.
5. A circuit with a three-cell battery and two bulbs,
each of which are controlled independently by a
switch.
Practice 1
• Draw a schematic in a circuit made from:
– A battery
– 2 light bulbs
– A switch
– Conductors (Wires)
Practice 2
• Draw a schematic diagram in a series including
these things
– Resistor
– Switch
– Voltmeter
– Fuse
– Battery made of 3 cells
Practice 3
• Draw a schematic diagram in parallel with the
following:
– 2 cells that power the whole circuit
– A light turned on by one switch
– 2 more lights turned on by a switch
together
– A third switch that turns on or off all the
lights together
Lets read!
• As a class read about House Wiring and
Microcircuits in your notes.
• What is a transistor?
• What is a microcircuit?
ELECTRICAL SAFETY
I can…
• Assess the potential danger of electrical
devices, by referring to voltage and current
rating (amperage) of the devices, and
distinguish between safe and unsafe activities.
Review
• What is the difference between static and
current electricity?
• What are some examples of conductors and
insulators?
• What four things do we need to have in a
circuit?
• Electricity moves through the path of least
resistance– where it is the easiest to flow
• A short circuit is a circuit where there isn’t any
protection and the electricity moves quickly and
can cause damage
• The 3rd prong on a cord leads to the ground and is
called a ground wire
• http://www.edumediasciences.com/en/media/486-grounding-earthing
• The number of amps of a current is more
important in terms of the danger of being
shocked
• Current from 0.015 A to 0.020 A will cause
a painful shock and loss of muscles control
• What does this mean for a person being
shocked?
The dangers of electrical shock
• To protect yourself from electric shock you
never want to allow electricity to run through
you
• Why are you safe in your car if a power line
fell on it?
• When are you not safe?
Factors affecting electrical shock
• Different situations affect how bad an
electrical shock is
• One a dry day with running shoes on you may
just feel a tingle from an electrical fence, but
the same fence on a rainy day when you are
barefoot could really hurt
Protecting yourself from Electrical
Shock
• Every plug in device in Canada must have a label
on it showing what voltage it requires and what
current it can use
• The higher these numbers the more harm it can
do
• http://www.youtube.com/watch?v=n6DXkVY8fzs
• http://www.youtube.com/watch?v=DtoQbXzNqk
g&list=PLyxsgbmjwCCkYdJ6Y2anojKwKXJVqiu9V
Plugs, Fuses and breakers
• Fuse: contain a very thin piece of metal that
will melt if too much current flows through it
stopping the circuit
– Need to be replaced (like in a car)
• Breakers- they “ short out” when too much
current is sent through them
– Need to be cooled (like in your home)
Danger of lightning
• A lightning strike can give a current up to 30 000 A
and it can kill
• Lightning usually strikes at the highest point on a
horizon
• Lightning rods are connected to the ground
through a wire to allow the discharge to dissipate
to the ground
• http://www.youtube.com/watch?v=RLWIBrweSU8
• http://www.youtube.com/watch?v=XKMdYbOfFzI
Demonstration
• Blow a Fuse!
• http://www.youtube.com/watch?v=ZT3HhDj8
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• http://www.youtube.com/watch?v=pJ9e4eaOi
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