- What is electricity?
- How does electricity get from one place to another?
- makes electricity so dangerous?
David conducts a study of electrical circuits.
Segment length: 9:01
When it comes to understanding electricity, to get to the heart of the matter you must
literally get to the heart of matter--the atom. Atoms are the building blocks of matter
and they are composed of three particle types. The central core of the atom is called
the nucleus and it contains positively charged particles called protons and neutral
particles called neutrons. The movement of many charged particles in the same direction
is called an electric current.
Charged particles flow most easily through conductors, such as metals, or through some
liquids, such as salt water. Electrons in metals are loosely attached to the atoms, so
they can move easily. The human body (which is mostly salt water) is also a good
conductor, which is why electric shocks can be so dangerous. Insulators, on the other
hand, do not conduct electricity well. Their electrons are tightly bound to their atoms
and do not move easily. Typical insulators include rubber, wood, glass, and most
Electricity will only flow when a power source, such as a battery or a generator, sets
the electrons in motion and when the electrons can complete a full circle. Consider
this example--electrons flow from a battery down a wire to a light bulb, through the
filament of the bulb, and then back up another wire to the battery. This closed loop
is called a circuit. No electrical device, whether it's a
simple flashlight or a complex computer, will work unless the circuit that delivers the electric current is a
Electricity becomes dangerous to you when you become part of the electrical loop--when
the electrons have enough energy and make adequate contact to pass through your body.
You can touch both ends of a flashlight battery and feel nothing, but if you're wet and
in contact with household electricity, water can make a very good path through your
skin and your body, making you part of the electrical circuit!
Electrical energy always seeks the shortest route around the circuit back to the source,
which in the above example is the battery. If the wires both touch a conductor, such as
a metal tabletop, the electrons will take that shorter route back to the battery,
rather than travel to the light bulb. (Conveniently, scientists call this a "short
So why don't birds get electrocuted when they sit on power lines? The power lines that
are suspended in pairs between power poles are analogous to the wires that run between
the battery and the light bulb. As long as birds sit on only one, they offer no
"shortcut" to complete the circuit. But if their wings accidently touch both adjacent
power lines, the electrons take a new path and complete the circuit through the
unfortunate bird's body!
- Imagine a world without electrical power. How would you cook, clean, and
- Even though electrical energy is useful, its production often causes
environmental problems. Acid precipitation from burning coal and disposal of nuclear waste are just
two of them. What are some alternative power sources and how can conservation help
minimize the damage?
circuit a closed loop of conductors through which
charges can flow
conductor a substance through which
electrical charges can easily flow
current a flow of electrical charges
generator a device for producing electrical current by moving a coil of wire in a
insulator a material through which electric
charges cannot move
ion an atom that has gained or lost one or more electrons and is thus a charged
switch a device that closes or opens a circuit, thereby allowing or preventing current
voltage the pressure behind the flow of electrons in a circuit
- Catherall, E. (1981) Electrical power. London: Wayland Publishers.
- Cooper, A. (1983) Visual science electricity. Morristown, NJ: Silver Burdett Company.
- Hewitt, P. (1992) Conceptual physics (2d ed.). New York: Addison-Wesley.
- Kluger-Bell, B. (1990, Fall) Pickle power: My search for the perfect homemade battery.
Exploratorium Quarterly, pp. 25-29.
- Math, I. (1981) Wires and watts. New York: Charles Scribner's Sons.
- Nye, B. (1993) Big blast of science. New York: Addison-Wesley.
- Stanley, L. (1980) Easy-to-make electric gadgets. New York: Harvey House.
- 3-2-1 Classroom Contact videotape: Generating Electricity. GPN: (800) 228-4630.
- VanCleave, J. (1991) Physics for every kid. New York: John Wiley Publishers.
- Vogt, G. (1986) Generating electricity. New York: Franklin Watts Publishing.
- Williams, J. (1992) Projects with electricity. Milwaukee: Gareth Stevens Children's
Local power utility
Which common objects are insulators and which are conductors? To test it for yourself,
you can build a simple, battery-powered conductivity tester.
flashlight with one fresh D cell
3 pieces of insulated wire, each approximately 15 cm (6") long with the ends stripped
roll of masking or duct tape
several pieces of fabric
metal fork or spoon
several different rocks
various objects for testing
- To build your tester, unscrew the top of the flashlight which has the bulb assembly
in it. Take one wire and tape it to the metal tip of the light bulb and tape a second
wire to the metal ring that touches the side of the bulb.
- Tape the other end of the wire connected to the tip of the light bulb to the (+)
end of a D cell and touch the free end of the second wire to the (-) end of the cell.
The light should go on because you have completed a circuit. If it doesn't, make sure
all the connections are taped tightly and make good contact.
- Tape one end of the third wire to the (-) end of the cell and touch its free end to
the free end of the wire coming from the bulb holder. Again, the light should go on.
Try touching the two free ends of the wires to the penny at the same time. The bulb
should light because the penny is made of copper, a good conductor.
- Collect your objects to be tested and predict if they are insulators or conductors.
Then try them out with your tester.
- In general, what types of materials make the best conductors?
- Look inside the body of the flashlight. How does the switch control make
the light go on and off?
Build an electromagnet using a D cell, a large steel nail, and about 50 cm (20") of
insulated wire. Strip the insulation off two ends of the wire and carefully wrap the
wire around the nail to form tight coils. Don't overlap the coils and make sure that
you leave at least 6 cm (2.4") of wire free at each end. Connect the two ends of the
wire to the two ends of the D cell and bring the tip of the nail very near some metal
paper clips. The magnet will only attract if the circuit is complete.
Examine your family's electric bill. What is a kilowatt? How much does the electric
company charge for one kilowatt hour? Is that a constant rate? Make a list of the
appliances that you think use the most electricity. Contact the electric company to see
if you are correct. Does your family use the same amount of electricity each month? Why
or why not?
Static electricity can do more than make your socks stick together. You can use it to
light a fluorescent tube. Get a small fluorescent bulb and a balloon. In a darkened
room, rub the balloon on your hair a few times. Bring the charged balloon near one end
of the bulb and you should see some light flashes.
Newton's Apple is a production of KTCA Twin Cities Public Television. Made possible by
a grant from 3M. Educational materials developed with the National Science Teachers