Download Electricity

You also need to study the 3 note
packets on static electricity &
current electricity.
Study Guide Key
Electricity
Chapter 17
1. Draw an atom and label the following parts: nucleus, proton, neutron, electron.
2. Match the subatomic part to its charge:
__c___ one proton
__a___ one neutron
__b___ one electron
a. zero
b. –1
c. + 1
3. If an atom has six protons and eight electrons, what is its charge?
-2
4. If an atom has five protons and three electrons, what is its charge?
+2
5. How are charges produced on an atom? What moves? What doesn’t?
The movement of electrons produce charges on atoms. The protons and neutrons in
the nucleus are strongly held together. They cannot go from one atom to another. But
the electrons orbit the nucleus, and the forces holding them in place are not as strong.
So, they are able to move from one atom to another.
If electrons move off an atom so that it has more protons than electrons, the atom is
positively charged. If the electrons move onto an atom, so that it has more electrons
than protons, it is negatively charged.
6. What does the Law of Electric Charges say?
Object that have opposite charges (one positive and one negative) attract one another.
There is a force that pulls them together.
Objects that have the same charges (both positive or both negative) repel one another;
they push apart from each other.
repel
repel
attract
7. What is static electricity?
Static electricity is when charges build up on an object. It is different from current
electricity, which runs in wires. Examples of static electricity are clothes sticking
together when you pull them out of the dryer, or when you comb your hair and your hair
starts to fly up to meet the comb.
8. List three ways to create a static electricity charge and define them.
a. Friction: when two uncharged objects rub against one another and the electrons
move from one of the objects to the other. This makes one of the objects have a
negative charge (the one that stole the electrons) while the other has a positive
charge (the one that lost the electrons).
b. Induction: when a charged object comes close to an uncharged object, and
causes that object to be charged. When you place a negatively-charged balloon
near a wall, the electrons in the top layers of the wall “run away” or are
REPELLED by, the balloon, because both the balloon and electrons are
negatively charged. When the electrons are repelled, the nuclei of the atoms
remain. Since the nuclei of atoms are made of positive and neutron particles
only, the wall becomes charged: a positive charge on the side where the balloon
is approaching, and negatively on the other side.
For a simulation of this, go to this website:
http://phet.colorado.edu/en/simulation/balloons
c. Conduction: when a charged object touches (comes in contact with) an
uncharged object, and the electrons move from the uncharged object to the
charged object. In this case, both objects end up with the same charge.
9. What is electric discharge?
When static electricity charges are removed from objects.
10.
What is an example of quick electric discharge? Slow electric discharge?
Fast: lightning, when we “shock” ourselves or others after shuffling our feet on the
carpet
Slow: when socks fall off the sweater it became attracted to through static friction while
in the dryer
11.
What three things are necessary to create a circuit?
1. A source of energy, like a battery or the energy from the electric company
2. A load (light bulb, television, refrigerator)
3. Conductive wires to connect the load and the energy source, and create the
circuit
12.
What is a load, on an electrical circuit?
Anything that is powered by current electricity
13.
What is a “filament” in an incandescent light bulb? What is it made of?
The filament is the thin wire that connects the two small posts in a light bulb. It is made
of tungsten, which is a metal element.
14.
What is the difference between a complete circuit and an incomplete
circuit? Draw examples of both.
A complete circuit is unbroken. It allows the electrons to run from the energy source,
through the load, and back to the energy source. An incomplete circuit has a break in
it. The electrons are prevented from making the complete route.
complete circuit
incomplete circuit
15.
What is the difference between an open circuit and a closed circuit? Draw
an example of each.
Both an open circuit and a closed circuit contain a switch. In a closed circuit, the switch
is closed (in the “down” position), so that the electrons can travel through the circuit,
and the power the load. In the open circuit, the switch is open, meaning it causes the
circuit to be incomplete. The electrons can’t go along the full route, and the load cannot
be powered.
light on
light off
closed circuit
open circuit
16.
Is an open circuit a complete circuit or an incomplete circuit? Explain your
answer.
It is an incomplete circuit. When the switch is in the “open” position, there is a break in
the “track” for the electrons to go along.
17.
What is a series circuit? Draw an example of a series circuit.
A series circuit has more than one load on a single circuit. It may, or may not have a
switch, but it has an energy source, at least two loads, and conductive wires to connect
them. The loads go one after another, along the track.
18.
What is a parallel circuit? Draw an example of a parallel circuit.
A parallel circuit also has more than one load, but each load has its own track.
19.
What are the advantages of a parallel circuit over a series circuit?
 More power to each of the loads
 You don’t have to choose to have everything on, or everything off
 When one load malfunctions (like one light bulb going out), everything else can
still work.
20.
What is a conductor? Give three examples of a conductor.
A conductor is a material that allows electrons to flow freely through it, and therefore
allows electricity to move through it. Most metals are good conductors. Most of the
wiring in our houses is copper. Silver is one of the best conductors, but it is very
expensive. Graphite, the material used to make “lead” for pencils, is also a good
conductor.
21.
What is an insulator? Give three examples of an insulator.
An insulator is a material that doesn’t allow electrons to flow freely through it, and
therefore, does not allow electric charges to go through it. Glass is a good insulator,
and is used in electric companies to protect workers from the current. Rubber and
plastic are both good insulators, and are often used to cover wires in our appliances.
22.
What is resistance?
Resistance is the term we use for when a material DOES allow electric charges to
move through it, but it slows them down, and causes a back-up of the charges, like a
traffic jam.
Some resistors (materials that have resistance) are very useful to us. Tungsten, the
metal used to make the filament in light bulbs, is a resistor. But tungsten has a very
special property: when electric current goes through it, and the charges get bunched up
because of its resistance, the friction of all those charged atoms bumping into one
another causes it to glow. That’s why we use tungsten for light bulbs.
23.
We can say that conductors, insulators and resistors fall on a continuum.
Draw a diagram to show what that means.
24.
What is voltage?
Voltage is the force that pushes electrons through the circuit. It is measured in units
called volts. The power source supplies the voltage.
25.
What is electrical current?
Electrical current is the flow of electrically charged particles. It is a measure of how
many electrons pass a point in a second. It is measured in units called amps.