Exhibit Profile: Bridge of Fire
Location: Level 2, Science Phenomenon Floor
Topic: Electricity, Charge, Static Electricity
Description:
With one hand, visitors touch a large metal tube connected to a Van
de Graaff generator. While touching it, their hair or the streamers of a
pom-pom held in their other hand will stand up.
SAFETY WARNING: The Bridge of Fire can only be operated by
education staff at the Great Lakes Science Center. Please find a staff
member if you wish to experience this exhibit.
Try This:
 Place your hand on the horizontal tube and wait.
o Pay attention to what you feel and hear.
 If you are carrying a pom-pom, hold it gently and look at the handle.
o Also try holding the pom-pom tightly and observe any differences you see or feel.
 For a bit of fun, touch the metal poles as you leave the Bridge of Fire.
o Careful, though! You will feel and hear a jolt as you discharge.
o The volunteer or staff member running the Bridge may also offer to discharge you.
o No matter what, as soon as you step off, you will be grounded and the unbalanced
charge will leave.
Questions to Ask:
 Can you feel the electricity flowing?
 Can you hear the electricity?
 Why do the sparks hurt? And why shouldn't you shock people without asking?
 What makes your hair or the strands of the pom-pom stand up?
 What might make the Bridge of Fire less effective at making hair or streamers stand up?
 Why do you think the Bridge of Fire behaves differently on humid days than on dry days?
 Why are batteries unsafe to take on the Bridge of Fire, but metal items are generally safe?
 Why do you remain charged while you're on the Bridge of Fire, even if you are not touching the
horizontal tube?
◦ What makes the imbalance stop once you step onto the floor, even if you do not touch
anything or anyone?
 Where is the charge running on your body?
Explanations:
The main component of the Bridge of Fire is an electrostatic generator called a Van de Graaff
generator, which consists of a hollow round conductor supported by an insulated column. In the
base of the generator is a motor that operates a pulley running through the full structure. A
conductor in the base carries a high voltage, usually 50,000 volts, pulling electrons off the belt.
This makes the belt carry a positive charge, which it transfers to the round metal conductor at the
top by attracting electrons from it.
The horizontal tube of the Bridge of Fire is linked to the Van de Graaff generator, and therefore
has a positive charge as well. Visitors touch the tube and electrons are pulled off them as well,
inducing a positive charge. Positive charges repel other positive charges making positively
charged hair and streamers move away from other hair and streamers, overcoming the force of
gravity. While electrons are very tiny and carry a very small charge, every object has an
inconceivably large number of electrons in it. The force of two electrons repelling is also not large,
but the combined force of billions and billions of them can produce hair-raising effects. The big
idea of this exhibit is that the charge itself does not actually matter. Rather, a difference in charge
causes the effects. The effects would be the same if the Bridge of Fire induced a negative charge.
Great Lakes Science Center | 601 Erieside Ave| Cleveland, Ohio | 44114
Exhibit Profile – Bridge of Fire, 2014
Explanations (continued)
The sparks generated by the Bridge of Fire are really no more harmful than the jolt you might get
from a doorknob after shuffling on a carpet. These sparks are tiny lightning bolts and paths for
electrons to jump from a negative to a positive charge. Air is a poor conductor, so a substantial
imbalance of charge must be present for a spark to be generated. This is why batteries are not
allowed on the Bridge of Fire. The imbalanced charge may overload and damage batteries. The
exhibit is safe for you, however, because the charges do not flow through you. The charges
actually flow on you, never reaching below your skin.
Related Exhibits at the Great Lakes Science Center:
 Hand Battery, to learn more about current, charge and conduction.
 Energy vs. Power, to learn about an application of charge and current.
 Plasma Ball or Lightning Tube to learn more about charge and static electricity.
 Giant Meter, to learn more about current and charge, and how magnetism affects electricity.
 Jacob's Ladder, to see visible electrical discharge, as you may have seen on the Bridge of Fire.
 Breadboard Circuits, to learn more about current.
 Ohm's Law, to learn about how charges behave and the math of electricity.
 Transformer, to learn about the connection between magnetism and electricity.
Try It at Home:
 The effects of the Bridge of Fire are the same effects as rubbing a balloon on your hair or
shuffling your feet on a carpet and then touching a doorknob.
◦ With a balloon, you can make your hair stand up, like on the Bridge of Fire. The difference is
that the hair-raising effect is limited to hair touching one side of the balloon.
 Static electricity is also generated by old TVs and computer monitors. You can sometimes hear
the static electricity crackle when an old TV is turned on. Modern televisions and monitors do not
generate noticeable static electricity on their screens.
Real-World Applications:
 The Bridge of Fire operates under the same principle that lightning does. The small sparks you
might see with the Bridge of Fire are lightning, but at a much smaller scale.
 Static electricity and the build-up of unbalanced charge is a challenge in engineering. Friction in
machines can generate electrical imbalances. These imbalances can be a nuisance or a danger,
particularly in delicate machines, so engineers must implement safeguards to prevent dangerous
imbalances of charge.
 Van de Graaff generators are occasionally used in particle accelerators, generating an imbalance
of charge that launches subatomic particles toward a target, to study the nature and behavior of
such particles.
 Electric forces are inherent to atoms. Electric forces interact between atoms and/or molecules to
form substances, metabolic processes such as protein synthesis depend on electric forces, and
nerves carry electrical signals. Even physical interactions such as a ball striking a bat involve the
repulsion of electrons.
Vocabulary:
 Electric charge: An imbalance of the concentration of electrons in a material. A positive charge
results from a lack of electrons, while a negative charge results from an excess of electrons.
◦ Opposite charges attract while identical charges repel.
 Discharge: The release of charge, often as a result of an imbalance of charge.
 Ground: A connection between a conductor of electricity and the Earth. The Earth is so large that
it serves as a reservoir of both positive and negative charge, and can balance any imbalance of
charge if a conductor is linked to it.
 Static Electricity: A build-up of stationary electric charge on an object. Both conductors and
insulators can build electric charge,
Great Lakes Science Center | 601 Erieside Ave| Cleveland, Ohio | 44114
Exhibit Profile – Bridge of Fire, 2014
Vocabulary (continued)
 Conductor: A material in which electrons are loosely bound to atomic nuclei and are free to move
within the material, allowing for quick movement of electrons. Metal, impure water, and glass are
good conductors.
 Insulator: A material in which electrons are tightly bound to atomic nuclei and are not free to
move, preventing movement of electrons. Rubber, plastic, and wood are good insulators.
 Van de Graaff generator: A machine that generates an imbalance of charge using a motorized
belt, conductor, and power source. The Van de Graaff generator was invented in 1929 by Robert
J. Van de Graaff, an American physicist.
Ohio Revised Science Standards:
Physical Science
Grade 3: Matter and Energy: Heat, electrical energy, light, sound and magnetism are forms of energy.
Grade 4: Electricity, heat and matter: Energy can be transformed from one form to another or can be
transferred from one location to another.
Grade 5: Light, sound and motion: Light & sound are forms of energy that behave in predictable ways.
Grade 7: Conservation of mass and energy: Energy can be transformed or transferred, but never lost.
Energy can be transferred in a variety of ways.
Grade 8: Forces and Motion: Forces between objects act when the objects are in direct contact or when
they are not touching. Forces have magnitude and direction.
Great Lakes Science Center | 601 Erieside Ave| Cleveland, Ohio | 44114
Exhibit Profile – Bridge of Fire, 2014