Einstein's Big Idea
Students explore the meaning of E in E = mc2 by
investigating the nature of fields and forces at different stations in the
Students will be able to:
explain what the E in E = mc2 represents.
name different kinds of energy.
show examples of how one kind of energy can be converted into another
kind of energy.
describe how a field can exert a force and cause an object to move.
Materials for each station
- several plastic spoons
- 10 cm x 10 cm piece of wool or rabbit fur
- pieces of plastic foam cup, crumbled into bits
- pieces of paper, about 0.5 cm by 1 cm each
- bar or horseshoe magnet
- small shallow cardboard box
- piece of white paper (cut to fit box)
- iron filings in small jar or beaker
- 40 cm of well-insulated copper wire
- 6V lantern battery
- 2 large nails
- small paper clips
(mechanical to heat energy)
- 8 oz bottle of glycerin
- two 8 or 10 oz plastic foam cups
- 2 metal spoons
- 2 alcohol thermometers
- clear tape
- paper towels
(electrical to heat energy)
- 2 pieces of insulated wire, each 20 cm long
- one 1.5V battery
- small light-bulb socket and 4W bulb
(potential to kinetic to mechanical energy)
- 2 metal pendulum bobs
- 60 cm string, cut in half
- ring stand, ruler, or meter stick
(chemical to heat energy)
- 2 wood splints of same weight
- two 500 ml beakers
- pan or triple-beam balance
- long wooden matches and goggles (for teacher only)
- copy of the "Energy's Invisible World" student handout
- copy of the "Station 1-3 Instructions" student handout
- copy of the "Station 4-7 Instructions" student handout
= mc2 sprang from the work of men and women dedicated to
revealing the secrets of nature.
of the scientists integral to the equation's E was a young bookbinder
named Michael Faraday. A self-taught scientist, Faraday helped reshape the idea
of energy. In the early 19th century, scientists saw nature in terms
of individual powers and forces, like wind or lightning. Scientists were
puzzled when they placed a compass next to a charged wire and its needle was
deflected at right angles. Faraday visualized an answer no one could
believe—that the compass was being affected by invisible lines of force
flowing around the wire. Through a groundbreaking experiment involving
electricity and a magnet, Faraday demonstrated the existence of these lines of
force. His work served as the basis for the electric engine. It was Faraday's
ability to see a problem in a new way that led to this breakthrough.
In this activity, students explore different aspects of energy, energy fields,
the forces that fields exert on other objects, and how energy is transferred
from one form to another. Students move through a series of stations where they
do mini-activities and make observations.
Energy can be a difficult concept to define for younger students. Usually
defined as the ability to do work, the definition can be made clearer when
students examine what energy does in a physical sense. Work is done when
an object has a force exerted on it and the object moves a distance. So, in the
simplest possible terms, energy is expended when work is done, and energy is
often transferred and appears in a different form (i.e., electric potential
heats up a light bulb filament; heating the filament produces light and heat
A field is region of space characterized by the existence of a force. The
easiest field for students to understand is Earth's gravitational field, which
is responsible for objects falling. When a ball is dropped, the field exerts a
force that accelerates the ball and moves it toward Earth in the same way that
the north pole of a magnet exerts a force on the south pole of another magnet.
The work that the field does is converted to energy of motion of the ball, and
then to heat when the ball hits the ground. At several stations in this
activity, students will examine what fields can do in terms of exerting forces
and doing work. Conservation of energy is also explored.
conservation of energy: A law stating that the total amount of energy
in a closed system stays constant.
electric field: A region of space characterized by the presence of a
force generated by an electric charge.
electromagnet: A magnet created when an electric current flows through a
coil of wire; magnetism does not occur when the current is off.
field: A region of space characterized by the existence of a force.
kinetic energy: The energy due to the motion of an object.
magnetic field: A region of space characterized by the presence of a
force generated by a magnet. A magnetic field is also produced by a flowing
potential energy: The energy an object has due to its position or
condition rather than its motion.
work: The amount of energy involved in exerting a force on an object as
Set up the stations in advance of the activity. Place station labels (with
station numbers only) at each location.
Station 1 (electric field): Supply plastic spoons, wool or rabbit fur,
bits of plastic foam cup, and paper.
Station 2 (magnetic field): Place the piece of paper in the box and the
box on top of the magnet. Situate the container of iron filings nearby.
Station 3 (electromagnet): Using the center of the wire, tightly coil
the insulated wire around one nail, leaving about the same amount of wire on
either side, and place the battery nearby. (The strength of the nail's magnetic
field is proportional to both the battery current and the number of coils of
wire around the nail.) Place the second nail and the paper clips at the
Station 4 (mechanical to heat energy): Place 100 milliliters of glycerin
in each plastic foam cup. Place metal spoons, alcohol thermometers, tape,
magnifying glass, and paper towels at the station. Have student teams alternate
cups of glycerin (each with its own spoon and thermometer) so that one cup will
have time to cool while the other is being used.
Station 5 (electrical to heat energy): Set up a circuit similar to
Station 3, but place a small socket and light bulb in place of the
Station 6 (potential to kinetic to mechanical energy): Set up two
pendulums of exactly the same length. Tie them from the same point on a ring
stand or from a ruler or meter stick that can project over the desk
Station 7 (chemical to heat energy): Do as a demonstration before
students visit stations. Put goggles on. Choose two splints of the same weight.
Burn one in a beaker by lighting it at its center (relight if needed until the
splint is completely burned). Ask students to share their ideas about any
energy changes that took place. Set up the balance so students can weigh each
Organize students into teams and distribute the student handouts.
Brainstorm with students about different types of energy. Ask them how many
energy sources they use each day. Review each kind of energy (and any
associated fields) with students. Write the equation E = mc2
on the board and ask students what kind of energy they think Einstein was
referring to in the E in his famous equation.
Review safety protocols for Stations 3 and 5. Caution students not to leave
wires connected to the battery for more than 30 seconds. The battery, the
electromagnetic nail, and the wire in Station 3 will get fairly hot, as will
the battery and light bulb in Station 5. Supervise students as they complete
Have student teams rotate through all the stations, and facilitate if
needed. After completing all the stations, have students individually answer
the questions on the "Energy's Invisible World" handout. Then have students
discuss their answers as a team. Once all teams are done, go through each
station, discuss what kinds of forces and energy transfers occurred, and
reconcile any differences in student answers. (See Activity Answer for more
information.) If students are having trouble with the idea of conservation of
energy, help them understand what parts are contained in each system they
studied and clarify the differences between open and closed systems. Conclude
by revisiting the E = mc2 equation and asking students again
what the E in the equation stands for. (Any manifestation of energy in a
As an extension, have students further explore electromagnets. Announce a
contest-a prize to whoever can pick up the most paper clips. Leave a pile of
batteries, nails, and wire on the table and let students design their own
electromagnets. The ones that catch on will use multiple nails as a core and
place more coils of wire around their nails to strengthen their
following is a description of what is occurring at each station.
Station 1: Students are examining the effects of an electric field
produced by rubbing a plastic spoon on fur. Once the spoon is charged
(negatively), it will attract an uncharged object like a piece of paper through
electrostatic induction. The large negative charge on the spoon repels the
electrons in the piece of paper and leaves the side of the paper near the spoon
slightly positive. (Positive charges-in the nucleus of each atom within the
paper-hardly move at all.) Then, the negative spoon attracts the now positive
side of the paper. If students are careful in their approach to the paper, they
should be able to make it "dance."
Plastic foam becomes instantly negatively charged when in contact with another
negatively charged object. The bits of plastic foam acquire a negative charge
when they touch the spoon and are repelled immediately. It is impossible to
catch a piece of plastic foam, no matter how close to the spoon it is held. If
students claim they can, have them recharge their spoons (the charge leaks away
quickly on humid days).
Station 2: Students should realize that the field from the magnet is
exerting a force on the iron particles. Student diagrams should show the
filings aligning to the north and south field lines. Students may need to be
generous with the iron filings to observe any patterns. If the magnet is weak,
have students place it under the paper in the box rather than under the box.
Station 3: The point of this station is that the magnetic field can do
work. It can lift objects as the energy of the field is transferred to the
paper clips. The electromagnet at this station can be the catalyst for a
discussion of how electricity and magnetism are linked.
Station 4: This station shows how mechanical energy (stirring of the
glycerin) can be turned into heat energy. (Students' muscles also generate heat
as they work to stir the glycerin.) Students need to read the thermometer very
carefully. Temperature changes of only a few tenths to one degree are
Station 5: The light bulb demonstrates how electrical energy can be
converted to light and heat energy. Most of the light bulb's energy is given
off as heat. If you have time, you may want to discuss how a battery works-that
it hosts a chemical reaction and that the energy of that reaction supplies the
electrical energy when a battery is connected to something.
Station 6: The pendulum presents an example of multiple energy
transfers. The work students do when they lift the pendulum up is stored as
potential energy. When released, the potential energy is converted throughout
the arc to kinetic energy. At the bottom of the arc, the pendulum now has
converted all its potential to kinetic energy. The kinetic energy is then
converted into mechanical energy (plus a bit of heat and sound energy—the
"click" heard on impact) when the moving bob hits the stationary one. The
motionless bob, when struck, then transfers the mechanical energy to kinetic
and moves in an arc until the kinetic is converted to potential energy and the
bob stops and swings back down again. With each swing, the pendulum bobs swing
lower and lower. This is due to friction at the pivot point, in which small
amounts of energy are being converted to heat, and to air resistance (which
also creates friction). If there were no friction, the pendulum would swing
forever. (Students may miss the fact that, initially, it is the food they eat
that gives them the energy to use their muscles to exert the force and supply
the energy to lift the pendulum bob. Even earlier in the process, it is the
sun—an example of E = mc2—that provided the
energy that made their food possible.)
Station 7: This demonstration is the most complex of the energy change
scenarios in this activity. If students have had a limited exposure to chemical
reaction, such as the combustion of wood, this would be a good time to review
students' observations in detail. Discuss what the reactants of this combustion
reaction are (wood and O2), and what the products of the reactions
are (carbon, CO2, and water).
Student Handout Questions
At which station(s) did you observe the following field effects?
a) a magnetic field exerted a force on an object (Stations 2, 3)
b) an electric field applied an attractive force on an object (Station
c) an electric field applied a repulsive force on an object (Station
d) an electric field caused the formation of a magnetic field (Station 3)
which station(s) did you observe the following energy transfers?
a) mechanical energy to heat energy (Station 4)
b) electrical energy to heat energy (Stations 3, 5)
c) potential energy to kinetic energy (Station 6)
d) mechanical energy to kinetic energy (Station 6)
e) kinetic energy to mechanical energy (Station 4*, 6)
f) chemical energy to heat energy (Station 7)
g) kinetic energy to sound energy (Station 6)
h) electrical energy to light energy (Station 5)
*This one is a bit tricky. Students may not consider moving a spoon in
glycerin to be energy but of course it is. At Station 4, mechanical energy
(hand moving) is converted to kinetic energy (motion of the spoon) and then to
mechanical energy (spoon moving through glycerin) and finally, to heat energy.
Stepping back further, students eat food (chemical potential energy) that
enabled their muscles to move the spoon.
At which of the stations did you observe one kind of energy being
converted to more than one other kind of energy? Draw a simple diagram to show
the steps in the conversion of energy at each of these stations.
Station 5: electrical energy => heat and light energy
Station 6: mechanical energy (picking up the pendulum bob) => potential
energy => kinetic energy => sound and mechanical energy (hitting the
second bob) => kinetic energy => potential energy
Station 7: mechanical energy (to light the lighter) => chemical energy
(burning gas) => light and heat energy => chemical energy (burning
splint) => light and heat energy
The law of conservation of energy says that energy cannot be created or
destroyed; the total energy in a closed system remains constant (a system is a
group of interrelated parts that function together as a whole). Design a
procedure showing how you would test this law by modifying the open-system
setups at Station 5, 6, or 7. Students may arrive at different ways to make
these open systems closed. At Station 5, an experiment would need to be
designed to capture and measure the heat escaping from the light bulb. At
Station 6, friction must somehow be accounted for, both friction from the air
and friction at the pivot. At Station 7, an experiment must be designed to
capture and measure the energy given off by the burning splint.
NOVA—Einstein's Big Idea
Hear top physicists explain E = mc2, discover the legacy of
the equation, see how much energy matter contains, learn how today's physicists
are working with the equation, read quotes from Einstein, and more on this
companion Web site.
All About Energy Quest
Presents how energy is a part of daily life.
Energy Kid's Page
Features various sections about energy, including what it is and the forms
it takes. Includes time lines, facts, and a quiz about energy.
Energy Projects for Young Scientists
by Richard C. Adams and Robert Gardner. Franklin Watts, 2002.
Offers instructions for a variety of projects and experiments related to solar,
thermal, electrical, kinetic, and potential energy.
The Hidden World of Forces
by Jack R. White. Putnam, 1987.
Discusses some of the forces at work in the universe, such as electromagnetism,
gravitation, surface tension, and friction.
Kinetic and Potential Energy: Understanding Changes Within Physical
by Jennifer Viegas. Rosen Publishing Group, 2005.
Uses everyday examples to explain the concepts behind kinetic and potential
Stop Faking It!: Energy
by William C. Robertson. NSTA Press, 2002.
Provides information and activities to help teachers and students understand
concepts related to energy.
The "Energy's Invisible World" activity aligns with the following National Science
Education Standards (see books.nap.edu/html/nses).
- Motions and forces
- Conservation of energy and the increase in disorder
Classroom Activity Author
Lockwood taught high school astronomy, physics, and Earth science for 28 years.
He has authored numerous curriculum projects and has provided instruction on
curriculum development and science teaching methods for more than a decade.