ELECTRICITY
Electric Fence
Experiment.
Can you guess what
will happen?
What would life be like without electricity?
List 4 things that you would miss the most:
1) ______________________________
2) ______________________________
3) ______________________________
4)
______________________________
Atomic Structure
Electrons
negative
Protons
positive
Neutrons
neutral
Positive and Negative Charge
when objects have excess
electrons, they become
negatively charged
Opposites ATTRACT
Objects with the same
charge REPEL
Static electricity occurs
when electrons transfer
to your clothes or hair
and give them a
charge. When you touch
something, the charge is
released, causing a "jolt"
Each hair is negatively
charged and repels other
hairs.
Or balloons stick to the
cat
Electric fields surround every charge and can act
upon other objects (even without touching them)
The force created by this field can either
attract
or
repel
Conductor - material in which electrons
can flow freely
Ex. Metals, such as copper
Insulator - electrons do not move easily
through
Ex. plastic, rubber
What is Grounding?
Buildings often install lightning rods, which provide
a path for electrons to take to the earth, bypassing
the building and sensitive electronic equipment
What Is Electric Current?
- movement of electrons in a single direction
- measured in amperes (AMPS)
This diagram shows a simple LED driver circuit. When the
battery is connected the positive end of the battery pulls
electrons from the negative end of the battery and through
the circuit.
This circuit has
three basic
properties:
1. voltage
2. current
3. resistance
Circuit = a closed path that electric
current follows
This flow of electrons can power things
like light bulbs
Resistance = tendency for material
to oppose the flow of electrons
-- electric current loses energy as it flows
-- resistance is measured in OHMS
* Copper has a low
resistance, hence it is
used for household wiring
and other electronics
STOP AND THINK
1. A positively charged subatomic particle is ____
negatively charged subatomic particle is ____
2. Amperes are used to measure _________
3. A closed path that electrons (current) can flow
through is a:
4. Materials that current can flow through easily are
called:
5. OHMS are used to measure the __________ of a
circuit.
As the length of a
wire increases, so
does its resistance
As the wire becomes
thinner, its resistance
increases
the thin wire in a
tungsten light bulb glows
due to this resistance
Ohm's Law -- the current (I) in a circuit
equals the voltage difference (V)
divided by resistance (R)
Quick Calculations:
1. What is the current (I) of a circuit with a voltage
difference of 20 volts and a resistance of 10 ohms.
2. What is the Voltage difference in a circuit with a
resistance of 11 ohms, and a current of 2
amperes.
Circuits
How many electrical devices can you see in this room? Name
2.
Circuits have:
1) source of voltage difference (battery or outlet)
2) device that uses the energy (light)
3) conductors (wires) form a closed path to device
Series Circuit
Example: A string of christmas lights, when one light burns out,
no lights will work. Why?
Because that burned-out bulb breaks the circuit to all the
bulbs.
Each bulb along the
path shares the
voltage, so the bulbs
may appear dim.
Parallel Circuits
Series circuits aren't a good way to wire a
house. If you turned off one light, then all
the lights would go out.
Parallel circuits contain two or more
branches
Disadvantage: Even when you turn a light
off, current continues to flow through the
system.
This is why you shouldn't stick a fork in an
electric socket!
Circuit Diagrams
=
=
A switch can break a circuit
And turn a device on or off
Does it matter
where you place
the switch?
Identify the type of circuit:
______________________
______________________
What is a fuse?
Fuses contain a tiny
piece of metal that
melts if the current
gets too high - this
breaks the circuit.
Too many appliances
on in one room can
overload the circuit and
blow a fuse.
Where does electricity come from?
Most electricity comes from converting heat energy into
electrical energy - burning fossil fuels such as coal and natural
gas.
Some electricity is generated from dams, and nuclear reactors
How do dams generate electricity?
As water flows
through the dam it
spins turbines, which
will create electricity.
These are referred to
as:
HYDROELECTRIC
DAMS
How are dams built?
How do they hold all that water back?
What happens when dams fail?
Cost of Electricity
1) Most companies charge by
the amount of energy used
2) This is measured in kilowatt
hours (kWh)
3) Each light bulb in your house
costs money to leave on!
4) Meters outside your house
measure how much energy is
used
Check out:
http://www.energyeducation.tx.gov/
What is the difference between
alternating current and direct current?
Check out
http://www.pbs.org/wgbh/amex/edison/
sfeature/acdc.htmlhttp://www.pbs.org/w
gbh/amex/edison/sfeature/acdc.html
AC = alternating current
DC = direct current
Direct Current is found in
simple circuits like a battery
powered flashlight.
AC current are used to
power large grids, like the
electricity that comes to
your home
AC vs DC Current
What is the problem with
AC current?
Why is it used for most
household electricity?
What is a microgrid?
Video: https://youtu.be/g17f9J1-r-k
QUIZ TIME:
Electricity
1. What happens when an object has an excess
number of electrons?
a) object is positive
b) object is negative
2. Name something that is a conductor:
3. What unit is electric current measured in?
4. What unit is electric energy measured in (think
power bill)?
5. The force that causes electrons to flow is the
____________ difference.
6. Is the image showing a
parallel or series circuit?
7. Where does the
electricity come from that
powers your house?
8. What causes a fuse to
be blown?
9. _________ Law can be
used to calculate voltage.
10. Resistance is the
tendency for ____________ to
oppose the flow
of ____________.