Electricity/Magnetism Study Guide
(use your notes to study as well)
1. What does the Law of Electric Charges say?
Objects 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
2. What is electric discharge?
When static electricity charges move off objects.
3. What three things are necessary to create a circuit?
1. A source of energy, (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
4. What is a “load”, in an electric circuit?
Any device that is powered by current electricity
5. 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 semiconductor metal.
6. What is the difference between an open circuit and a closed circuit? Draw an
example of each.
In a closed circuit, the switch is closed (in the “down” position), so that the electrons
can travel through the circuit, and then power the load. In the open circuit, the switch is
open, which causes the circuit to be incomplete. The electrons can’t go along the full
route, and the load cannot be powered.
light on
closed circuit
light off
open circuit
7. What is a series circuit? Draw an example of a series circuit.
A series circuit has more than one load on a single circuit. The loads go one after another,
along the track.
8. 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
9. 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.
10.
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. Aluminum
is good, but can’t handle the heat so is not safe in homes.
11.
What is an insulator? Give three examples of an insulator.
An insulator is a material that does not allow electrons to flow freely through it, and therefore,
does not allow electric charges to go through it. Glass and wood are good insulators.
Rubber and plastic are both good insulators, and are often used to cover wires in our
appliances.
12.
What is a semiconductor? Give 2 examples.
A semiconductor is a material that allows electrons to flow through it, but slows them down –
like “speed bumps”. Iron, the human body & tungsten are some examples of semiconductors.
13.
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.
14.
In a circuit, what is voltage?
Voltage is the force that pushes the charged particles around the circuit. Voltage is supplied
by the power source in the circuit. It is measured in Volts.
15.
In a circuit, what is current?
Current is the flow of electric charge in a circuit. It is a measure of how many electrons pass
a point in a second. It is measured in units called amps.
16.
We can say that conductors, insulators and resistors fall on a continuum.
Draw a diagram to show what that means.
17.
What is alternating current? What is our primary source of alternating
current? What is the benefit of alternating current? What is the problem with
alternating current?
Alternating current is electric current in which the charges continually switch from flowing in
one direction to flowing in the reverse direction. Power plants generate alternating current
(AC) which comes to the outlets in our home. The benefit of alternating current is that it can
travel long distances through wires. The problem is that many of our electronic devices
cannot use alternating current – they need direct current.
18.
What is direct current? What is our primary source of direct current?
Direct current is electric current in which the charges always flow in the same direction.
Batteries produce direct current.
19.
What is a diode?
A diode is an electronic device, made from semiconducting material, that converts alternating
current (AC) into direct current (DC).
20.
What does a transistor do?
Transistors are semiconductors that act like an electronic valve that can be used as an
amplifier or a switch. They can control how much current goes through a load, or they can
take an audio signal and amplify it before sending it to a speaker.
21.
What does an electric generator do?
An electric generator changes mechanical energy to electrical energy.
22.
To what materials are magnets attracted?
Magnets are attracted to iron, nickel, and cobalt. Since steel has iron in it, magnets will
attract steel as well.
23.
What are the magnet’s poles? How many poles does every magnet have?
Poles are the parts of a magnet where the magnetic force is the greatest.
All magnets have a north pole and a south pole. There are no magnets that have only one
pole. If you cut a magnet in half you will end up with two smaller magnets, each with a north
and a south pole
24.
State the Law of Magnetic Attraction.
Opposite poles attract, and like poles repel.
25.
What are magnetic fields?
Magnetic fields are the places where a magnet’s effects can be felt. They exist around all
magnets.
26.
What is an electromagnet? Explain how to make one.
An electromagnet is a temporary magnet created with electricity.
It is made with a solenoid, wrapped around an iron core, and attached to an energy
source.
27.
What is a solenoid?
A solenoid is a coil of wire that produces a magnetic field when it carries an electric
current.
28.
Name two ways to make an electromagnet stronger.
You can make an electromagnet stronger by either (1) looping more coils in the
solenoid or (2) increasing the current running from the power source.