Electricity
The Science Channel
“Understanding Electricity”:
https://www.youtube.com/watch?
v=tipublpl164&list=PL_OeXM6etJ63VcKmIO1MQuUmoNCMsh
PV
Background
• Remember that atoms have protons, neutrons and
electrons.
• Electrons are negatively charged particles that can
sometimes when the situation is just right, escape
from one atom and move to another!
• Movement of electrons is the basis of electricity
Static Electricity
• An electric shock that is caused by the buildup of
electrons is called static electricity
• Small amounts of static can cause a slight shock like
when you rub your feet along the carpet and touch
someone
• Large amounts of static can occur as in the case
when clouds discharge static electricity in the form
of lightning
Static Lab and Activity
Static Electricity Video:
https://www.youtube.com/watch?v=EPTrYsuE9sA
About Electricity
• The movement of electrons from one place to
another is called electric current
• Electric current is measured in amperes
• When electrons travel in an electric current they
follow a path called a current
Closed Circuits VS Open Circuits
• Electrons can only follow a complete, unbroken
path called a closed circuit
• Sometimes we DON’T WANT a closed circuit like
when we want to turn the lights out. To do this, we
can use an incomplete or Open Circuit
Confused???
• To make an open circuit into a circuit that we can
use when we want, we put in switches.
• When the switch is closed the circuit is now closed
so that electrons can flow in an unbroken path
• When the switch is open the circuit is now open
so that now the current cannot flow through
Switch
Switch
Conductors and Insulators
• A conductor is any material that electricity passes
through easily (metals are great conductors!)
• An insulator is any material that electricity does
NOT pass through easily (rubber, plastic)
• Electric wires normally have a center made of
conducting material but are coated with insulating
material
INSULATOR
CONDUCTOR
Resistance
• In electricity, resistance is the measure of how easy
or hard it is for electric current to move through a
material.
• Resistance is measured in Ohms
• Insulators have high resistance
• Conductors have low resistance
Resistance
Resistance of wire depends on 3 things:
1. The material the wire is made of (Copper is less
resistant than tungsten)
2. The length of the wire (longer=more resistance)
3. The thickness of the wire (thinner=more
resistance)
Resistance is GOOD sometimes!...It causes electrical
energy to turn into heat and light energy…without
resistance many appliances in our home would not
work!
What have you learned???
Answer the following questions in you notes
1. What is the difference between an insulator and a
conductor?
2. Why would it be dangerous to use a cord that had
it’s insulator destroyed?
3. What are three things that affect the resistance of
a wire?
Book Work!
In your Physical Science book: Read lesson one
and two then answer the questions on your
worksheet
Sources of
Electrical Current
• Something has to “push” electrical current in order
for it to move through a circuit.
• Electromotive force is the push that keeps the
current flowing. This is measured in volts
• When voltage is high, electrons have more energy
to do work
Check out your light bulbs and appliances at
home….how many volts do these things use?
Dry Cell Batteries
• Batteries are a source of voltage and change
chemical energy into electrical energy
Dry cell battery—the materials in this battery
are dry or paste-like
Look at the batteries in our class flashlights.
What kind are they? How many volts of
energy do they supply?
Dry Cell Batteries
Parts of a dry cell battery
• Positive terminal +
• Zinc can
• Paper liner
• Cardboard casing
• Carbon rod
• Manganese dioxide paste
• Negative terminal -
Wet Cell Batteries
• This is a source of electricity with a liquid center
• Most wet cell batteries have a hard rubber case
filled with a solution of sulfuric acid
Dry Cell Battery Parts Video:
https://www.youtube.com/watch?v=UEPJXSXw7HA
Wet Cell Battery video:
https://www.youtube.com/watch?v=4IgHj2Uim_0
Construct a Battery Activity
or
Make a Fruit Battery
Dry Cell vs Wet Cell Video
https://www.youtube.com/watch?v=gQOxWXRsLB4
Direct and Alternating Current
• When current flows in one direction it is called
direct current or DC
• Current in a wet or dry cell battery flow in one
direction.
• Current that changes direction regularly is
called alternating current or AC.
• AC is normally the type of electricity in most
homes
Ohm’s Law
• Volts, Current (amps), and Resistance (ohms) in an
electrical circuit are all related to one another
• Ohm’s Law helps us put this relationship into a
formula
Volts (V) = Current (I)x Resistance (ohms)
Or, more simply V = I x R
Other options: R = V/I or I = V/R
Let’s try out the Ohm’s Law Formula
(Yippeeeee!)
• An electric circuit has a 1.5 volt dry-cell battery and
a light bulb with 0.3 ohms of resistance. What is the
circuit’s current?
• Current = voltage/resistance
• Current = 1.5 volts/.3 ohms
• Current = 5 amps
Ohms Practice Worksheet
Series Circuit
• A series circuit is a circuit
in which all current flows
through different
electrical devices (such as
light bulbs) in a single
path
Draw a series circuit!
Series Circuit
Disadvantages
• If one light is unscrewed or burns out all of the
other lights will go out
• The more devices in the series, the less electricity
goes to each device (2 lights in a circuit would be
give off brighter light than 5 lights in a circuit)
Batteries in Series Circuits
• Batteries can be connected to series circuits and
will increase the voltage in the circuit
• To find the total voltage in a circuit that included
multiple batteries, add the voltages of each
battery together.
Fuses and Circuit Breakers in Series Circuits
• Homes that contain
series circuits have
fuses and circuit
breakers to protect
them
• Fuses and Circuit
Breakers in a series
circuit help prevent fires
YOUTUBE VIDEO
https://www.youtube.com/w
atch?v=LyekAmnJnOA
Fuses and Circuit Breakers in Series Circuits
If a wire gets too hot
the fuse will melt and
break the circuit.
Then the fuse must
be replaced
Circuit breakers are
switch-like devices
that can be reset
after the circuit has
been repaired
Do you know where
your house’s circuit
breakers or fusebox
is?
• Parallel circuits are circuits in
which there is more than one
path for current
• This can take more energy to
run but if one device burns
out, the others will keep
working
• When more electrical devices
are added to the same circuit
then more current runs
through it. As current
increases wires can heat up
and cause fires. Fuses and
circuit breakers can help
prevent this problem
Draw a parallel circuit!
Parallel
Circuits
Batteries in Parallel Circuits
• Batteries can be connected in parallel lines
which allows them to provide energy for a
longer amount of time
• A parallel connection does NOT increase the
amount of voltage in the circuit
Measuring
Electricity
• A watt is the unit used to measure electric power
(check out a light bulb…the watt amount is listed on
top of the bulb)
• Electric power is the amount of electrical energy
used in a given amount of time
• A Kilowatt-hour is a unit used to measure how
much electric energy is used (this is how many
1000s of watts used in an hour)
Bill Nye: Electricity
https://www.youtube.com/watch?v=BhYbmcbYJn8
Construct a Circuit Activity