5A - Electrostatics
10. Producing Static Charge
5A10.1 Rods, Fur, Silk, and Electroscope
An image of the electroscope can be projected onto the screen using a light point source.
[Set-Up Time: 5 min.]
5A10.2 Electrophorus
A metal disk can be repeatedly charged and discharged by setting it on a charged, insulated base. The effect can be shown by charging an electroscope.
[Set-Up Time: 5 min.]
20. Coulomb's Law
5A20.1 Suspended Conducting Rod
Show attraction or repulsion with a conducting rod which is suspended by string and can rotate freely.
[Set-Up Time: 5 min.]
5A20.2 Pith Balls
The pith balls can be projected onto the large screen using a light point source.
[Set-Up Time: 5 min.]
40. Induced Charge
5A40.1 Pith Ball and Charged Rod
An uncharged pith ball is initially attracted to a charged rod.
[Set-Up Time: 5 min.]
5A40.2 Charging an Electroscope by Induction
Touch an electroscope while holding a charged rod near it.
[Set-Up Time: 5 min.]
5A40.3 Deflection of Water Stream
A charged rod held near a stream of water will deflect it.
5A40.4 Kelvin Water Dropper
Water falls through two cans connected by an "X" arrangement to opposite receivers. When enough charge builds up on the cans, they discharge and light a neon lamp connecting them.
[Set-Up Time: 15 min.]
View of String of Lights Discharging: 
50. Electrostatic Machines
5A10.10 Wimshurst Machine
Two coaxial disks have small patches of metal along their perimeters. As they rotate in opposite directions, charge is collected from regions of imbalance and periodically discharged across an adjustable spark gap. The large machine has one fixed disk (requiring a slightly different geometry of conductors) and is turned by a motor. The small machine has two rotating disks and is turned by hand
[Set-Up Time: 5-10 min.]
5A50.30 Van de Graaff Generator
[Set-Up Time: 10 min.]
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5B - Electric Fields and Potential
10. Electric Fields
5B10.1 "Flox in Oil" Electric Field Display
Currently not in service.
Electrodes of various shapes are immersed in oil containing small particles of wool (flox). When a high voltage is applied, the flox orients itself along the field lines. This can be displayed with an overhead projector.
[Set-Up Time: 15 min.]
View of Projection on Wall: 
5B10.2 Hair on End
Charge yourself or a student using the Van de Graaff generator while standing on an insulated platform.
[Set-Up Time: 10 min.]
5B10.3 Van de Graaff Ping-Pong
A conducting ball suspended between the Van de Graaff (5A10.30) and a grounded sphere will bounce back and forth continuously. Works even better with the Wimshurst machine, 5A10.1.
[Set-Up Time: 10 min.]
5B10.4 Flying Pie-Tins
A stack of aluminum pie-tins is placed on top of the Van de Graaff generator. The pie-tins will lift up and float away one by one as the Van de Graaff is charged.
[Set-Up Time: 10 min.]
5B10.5 Extent of Electric Field
An electroscope placed several feet away from the Van de Graaff generator will register its charging and discharging.
[Set-Up Time: 10 min.]
20. Gauss' Law
5B20.1 Faraday Cage (with Van de Graaff)
Perform 5B10.4 "Extent of Electric Field" above, then cover the electroscope with the Faraday cage and show that the electroscope no longer responds.
[Set-Up Time: 10 min.]
5B20.2 Faraday Cage (with Tesla Coil)
A small neon lamp will light when placed within the field of a Tesla coil. Cover the lamp with the Faraday cage and the lamp goes out.
[Set-Up Time: 5 min; tesla coil currently unavailable.]
5B20.3 Faraday Cage (with Radio)
Show that a radio loses reception when placed within a Faraday cage.
30. Electrostatic Potential
5B30.1 Ball and Point with Van de Graaff
Show that a point discharges a Van de Graaff much more easily than a ball does.
[Set-Up Time: 10 min.]
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5C - Capacitance
10. Capacitors
5C10.1 Parallel-Plate Capacitor
A large, parallel-plate capacitor has one plate connected to ground and the other to an electroscope. The capacitor can be charged with an electrophorus, and the plate separation can be continuously varied.
[Set-Up: 10 min.]
With Plates Closer Together: 
20. Dielectrics
5C20.1 Capacitor with Dielectric
A dielectric (the University Phone Directory) is inserted between the plates of a charged capacitor, and the effect is observed on an electroscope.
[Set-Up: 10 min.]
With Dielectric in Place: 
5C20.2 Force on a Dielectric
A rider with a large dielectric attached above it is placed on an inclined air-track so that it is partially inserted between the parallel plates of a capacitor. When a high voltage is applied to the plates, the rider is pulled back up the track until the dielectric is entirely between the plates.
[Set-Up Time: 25 min.]
30. Energy Stored in a Capacitor
5C30.20 Short a Capacitor
A 1250 microfarad capacitor (or larger by request) is charged up and shorted with a screwdriver. Makes a loud, bright impression.
[Set-Up: 5 min.]
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5D - Resistance and Conduction
40. Conduction in Gases
5D40.1 Jacob's Ladder
Just like in 1930's horror movies! Two metal rods are arranged in a vertical V, and the potential difference between them is increased until a spark arcs across the base of the V. The air in its path, now ionized and hot, rises up the wires. Even as the rising spark gets much longer, the current still prefers to travel through the highly conductive ionized air, and so will maintain a stable arc all the way up the wires. The spark disappears as another forms at the base again.
[Set-Up Time: 5 min.]
5D40.2 Discharge with Flame
Discharge an electroscope by bringing the flame of a match nearby.
[Set-Up Time: 5 min.]
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5E - Electromotive Force and Current
40. Cells and Batteries
5E40.1 Voltaic Cell
Copper and zinc electrodes are placed in a diluted hydrochloric acid solution, and the resulting current is displayed on a galvanometer projected onto the screen. The separation between the electrodes can be varied, and the resulting change in current observed.
[Set-Up Time: 15 min.]
View of Meter Projection on Wall: 
5E40.2 Lemon-Powered Clock
A digital clock is powered by copper and zinc electrodes inserted into a lemon.
[Set-Up Time: 10 min.; Must provide lemon or request well in advance; currently out of service]
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5G - Magnetic Materials
20. Magnet Domains and Magnetization
5G20.1 Compass Array Model of Domains
An array of small compass needles shows domain structures. The array can be placed on an overhead projector.
[Set-Up Time: 5 min.]
5G20.2 Retentivity of Iron Toroid
Two soft iron cores form a split toroid with a few turns of wire around one half. When the coil is energized the iron is strongly magnetized. When the current is off, the two pieces are still difficult to separate, but once apart they no longer attract.
[Set-Up Time: 10 min.]
50. Temperature and Magnetism
5G50.15 Curie Point of Nickel
A chip of nickel is attracted to an iron magnet when cool, and falls away when heated with a propane torch.
[Set-Up Time: 10 min.]
5G50.50 Magnetic Levitation -- Meissner Effect
A small magnet will float over a superconductor cooled with liquid nitrogen.
[Set-Up Time: 10 min.; Must request one day in advance to get liquid N]
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5H - Magnetic Fields and Forces
10. Magnetic Fields
5H10.1 Oersted Effect
A compass needle is deflected near a current-carrying wire. Reverse the flow of current and the needle also reverses direction.
[Set-Up Time: 15 min.]
Motion of Compass Needle When Switch is Closed: 
5H10.2 Magnets and Iron Filings
Iron filings or an array of compass needles show the field lines due to various magnets. Displayed on the overhead.
[Set-Up Time: 10 min.]
View of Projection on Wall: 
5H10.3 Vertical Wire, Solenoid, and Iron Filings
Show the field lines around a wire or within a solenoid. Displayed on the overhead.
[Set-Up Time: 15 min.]
Setup: 
View of Projection on Wall: 
20. Forces on Magnets
5H20.1 Levitation Magnets
One ring magnet will float above another when oppositely oriented on a column.
[Set-Up Time: 5 min.]
30. Forces on Moving Charges
5H30.1 Cathode Ray Tube and Magnet
Deflect the beam in an open cathode ray tube with a bar magnet.
[Set-Up Time: 5 min.]
Spot Position Without Magnetic Deflection: 
With Magnetic Deflection: 
40. Force on Current in Wires
5H40.10 Force between Parallel Wires
Two parallel wires attract or repel depending on the direction of current flow.
[Set-Up: 15 min.]
5H40.15 Force on a Helix
A helix of copper wire will contract along its axis when current is passed through it.
[Set-Up: 10 min.]
5H40.35 One Wire in Magnetic Field
One wire is suspended between the poles of a U-shaped magnet. The wire jumps out when current is passed through it.
[Set-Up Time: 10 min.]
No Current: 
With Current: 
5H40.50 Barlow's Wheel
A vertical copper disk with current flowing from its center to a pool at its base will rotate when placed between the poles of a horseshoe magnet.
[Set-Up Time: not in service]
5H40.53 Unipolar Motor
A small magnet and nail suspended from a D battery are made to rotate when current from the battery is passed through them.
[Set-Up Time: 5 Min.]
50. Torque on Coils
5H50.1 Galvanometer Model
Demonstrate the torque on a current loop in a magnetic field, and show that the angular displacement in a galvanometer is proportional to the current.
[Set-Up Time: 10 min.]
With no current: 
With current: 
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5K - Electromagnetic Induction
10. Induced Currents and Forces
5K10.1 Induction Coil with Magnet
An induction coil connected to a galvanometer shows the current induced by inserting and removing a magnet.
[Set-Up Time: 10 min.]
5K10.2 Induction Coil with Electromagnet
Similar to 5K10.1 above, but an electromagnet is used in place of the magnet. The flux can be changed by either moving the electromagnet or varying the current through it. Also, an iron pole piece can be added.
[Set-Up Time: 15 min.]
5K10.3 Undefined Voltage Paradox
Two resistors of different resistance are attached together to form a ring, and the ring is placed around the core of a large, AC-powered coil. When an oscilloscope or a multimeter is connected to the two midpoints between the resistors, the voltage measured will depend on the actual path that the connecting leads take around the core.
[Set-Up Time: 25 min.]
20. Eddy Currents
5K20.1 Eddy Current Pendulum
A copper plate is free to swing between the poles of a large electromagnet. When the field is turned up, the plate will brake and quickly come to rest. The solid plate can be replaced with a comb-shaped plate, which diminishes the braking effect of the eddy currents.
[Set-Up Time: 25 min.]
5K20.2 Eddy Current Disk
A smaller version of the Eddy Current Pendulum 5K20.1 above. A rotating copper disk will slow down and stop when brought between the poles of a strong permanent magnet.
[Set-Up Time: 5 min.]
5K20.3 Jumping Rings
Copper and Aluminum rings will jump off a large, AC-powered coil. The rings can also be cooled in liquid nitrogen and will jump dramatically higher.
[Set-Up Time: 10 min.; Must request one day in advance to get liquid Nitrogen]
Available Accessories: 
5K20.65 Electromagnetic Can Crusher
A high energy capacitor discharges into a coil around an aluminum can. The eddy current in the can causes it to blow apart. This demo can also be used to show conduction in air, repulsion of opposite currents, and conversion of electrical energy to thermal energy.
[Set-Up Time: 15 min.]
30. Transformers
5K30.1 Dissectible Transformer
A model transformer can be connected to a sine-wave generator on one side and an oscilloscope (to be projected on the TV) on the other. One can change the number of turns in the coils and add or remove the iron core, and the effects are visible on the oscilloscope.
[Set-Up Time: 20 min.]
40. Motors and Generators
5K40.1 Large AC and DC Motor / Generator Models
Two very large demonstration models, complete with arrows showing the direction of the magnetic field. These are not functional--they are explanatory aids only!
[Set-Up Time: 5 min.]
5K40.2 AC and DC Motors
A single rectangular loop (there is an AC one and a DC one) acts as a motor when it is placed between the pole pieces of the large electromagnet and a current is sent through it.
[Set-Up Time: 15 min.; the AC motor is temporarily unavailable)
5K40.3 AC and DC Generators
A single rectangular loop (there is an AC one and a DC one) acts as a generator when it is placed between the pole pieces of the large electromagnet and cranked--the voltage or current generated is shown on a galvanometer and projected on the screen.
[Set-Up Time: 15 min.; the AC generator is temporarily unavailable)
Front View: 
Back View: 
Side View: 
Projection on Wall: 
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5L - AC Circuits
20. RLC Circuits - AC
5L20.1 Resonance in a Series RLC Circuit
A series RLC circuit is powered by a sine wave generator, and the voltage across the resistor is displayed on an oscilloscope. As the generator frequency is adjusted to the resonant frequency, the output voltage is seen to grow to a maximum.
[Set-Up Time: 20 min.]
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5M - Semiconductors and Tubes
20. Tubes
5M20.1 Fluorescence in Discharge Tube with Sea Shell
The name says it all: turn down the lights and apply the hand-held tesla coil to one end of the tube. Watch the surface of the sea shell fluoresce.
[Set-Up Time: 5 min.]
5M20.2 Electron Beam in a Discharge Tube
A horizontal discharge tube has a wall or screen running down its middle. At one end are two slits, and when a tesla coil is applied to that end, the electrons which go through the slits light up a path on the screen. Use a strong bar magnet to bend the path of the electrons.
[Set-Up Time: 5 min.]
Without Magnet: 
With Magnet:
5M20.3 Jacob's Ladder
A very long discharge tube with two parallel wires is held vertically and partially evacuated by an air-pump. One wire is grounded and a hand-held tesla coil is applied to the other wire. At the right (low) pressure, an arc will jump between the wires, and the arc will rise up the tube as the air heated by ionization rises.
[Set-Up Time: 40 min.]
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5N - Electromagnetic Radiation
10. Transmission Lines and Antennas
5N10.1 VCR to TV Broadcast
A two-meter dipole antenna is attached to the VHF output of a VCR. At the opposite side of the room, a similar antenna is attached to the VHF input of a TV. Set both devices to channel 3, insert a tape, and watch the broadcast. Demonstrate the polarization of the EM wave by rotating one of the antennas ninety degrees, cutting off the broadcast completely.
[Set-Up Time: 25 min.]
5N10.61 Dipole Array
A Mathematica notebook written by John M. Novak of Wolfram Research simulates the radiation pattern emitted from a linear dipole array. After the user specifies the geometry of the array, the notebook shows the 2-D far field pattern, the 3-D pattern (including coupling to the earth), and a 2-D pattern showing where the transition to far-field occurs.
[Set-Up Time: 10 min]
20. Tesla Coil
5N20.1 Tesla Coil
Stand alone or hand-held versions of the Tesla Coil are available. Draw large sparks, or light a fluorescent bulb in the vicinity of the coil.
[Set-Up Time: 5 min; currently not available]
30. Electromagnetic Spectrum
See: Optics page: 6F30.1 White Light and Prism.
5N30.20 Skin Depth
Wrap up a hand-held radio in aluminized mylar, and hold the mylar tight across the speaker so the sound gets out. If the radio is playing AM, the same levels are heard as without the mylar. If it is playing FM, the aluminum blocks the signal and only static is heard.
[Set-Up Time: 5 min]
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