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 Electricity and Magnetism View Printable Version

## 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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

### 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.]
[Current Condition: good]

5A20.2 Pith Balls
The pith balls can be projected onto the large screen using a light point source.
[Set-Up Time: 5 min.]
[Current Condition: Good]

### 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.]
[Current Condition: Good]

5A40.2 Charging an Electroscope by Induction
Touch an electroscope while holding a charged rod near it.
[Set-Up Time: 5 min.]
[Current Condition: Good]

5A40.3 Deflection of Water Stream
A charged rod held near a stream of water will deflect it.
[Current Condition: Good]

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.]
[Current Condition: good, but very dim]

View of String of Lights Discharging:

### 50. Electrostatic Machines

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.]
[Current Condition: Good]

## 5B - Electric Fields and Potential

### 10. Electric Fields

5B10.10 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.]
[Current Condition: Good]

5B10.13 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. A pie tin can be filled with puffed rice cereal to make a big mess instead.
[Set-Up Time: 10 min.]
[Current Condition: Good]

5B10.35 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.]
[Current Condition: Good]

5B10.40 Electric Field Display
A new apparatus has small wool particles suspended in oil between electrodes of different shapes. When voltage is applied, the particles align with the field lines. Shows point-point, point-plate, and plate-plate patterns. The apparatus is displayed with an overhead projector.
[Set-Up Time: 15 min.]
[Current Condition: good]

5B10.53 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.]
[Current Condition: Good]

### 20. Gauss's Law

5B20.12 Gauss's Law (Faraday Ice Pail)
Two concentric cylinders connected to an electroscope can be used to demonstrate Gauss's Law. Lower a charged object into a metal cylinder and demonstrate the induced charge is unaffected by position. Then touch them together and demonstrate all the charge was positioned on the outer surface.
[Set-Up Time: 15 min.]
[Current Condition: Unknown- current setup is non-functional and is on my list of things to update. please contact me if this is something you would like to use in the near future.]

5B20.13 Gauss's Law Electrode
Show the E field setup of 5B10.40, above, to show the field of a circular electrode.
[Set-Up Time: 10 min.]
[Current Condition: Good]

5B20.30 Faraday Cage (with Van de Graaff)
Perform 5B10.53 "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.]
[Current Condition: Good]

5B20.33 Pith Balls in a Cage
Charge up a cylindrical shell with acrylic/silk. Pith balls hung outside will repel the surface, but pith balls hung inside will do nothing.
[Set-Up Time: 10 min.]
[Current Condition: Good]

5B20.34 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.]
[Current Condition: Good]

Show that a radio loses reception when placed within a Faraday cage.
[Current Condition: Good]

### 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.]
[Current Condition: Good]

## 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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

### 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.]
[Current Condition: Good]

## 5D - Resistance and Conduction

### 10. Resistance

5D10.20 Playdoh Resistor
A lump of playdoh is connected to an ohmmeter, or in a series circuit. Molding it into various shapes changes its resistance in real time.
[Setup time: 15 mins.]
[Current Condition: does not work. give me advance notice, and I will try and track down various lengths/widths of wire as an alternative]

### 40. Conduction in Gases

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.]
[Current Condition: Good]

5D40.2 Discharge with Flame
Discharge an electroscope by bringing the flame of a match nearby.
[Set-Up Time: 5 min.]
[Current Condition: Good]

## 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.]
[Current Condition: Good]

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]
[Current Condition: broken]

## 5G - Magnetic Materials

### 10. Magnets

5G10.20 Break a magnet
It is very hard to remove the core of a strong horseshoe magnet.
[Setup time: 2 min.]
[Current Condition: Good]

### 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.]
[Current Condition: OK- some needles are misaligned]

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.]
[Current Condition: Good]

### Paramagnetism and Diamagnetism

5G30.20 Paramagnetism of (liquid) oxygen
A metal container is filled with liquid nitrogen; liquid oxygen condenses on the outside and drips off the bottom and into the gap between the poles of a magnet. The oxygen droplets will get caught and stay in the field.
[Setup time: 10 mins.]
[Current Condition: Good]

### 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.]
[Current Condition: Good]

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]
[Current Condition: Good]

## 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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

### 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.]
[Current Condition: Good]

Spot Position Without Magnetic Deflection:

With Magnetic Deflection:

5H30.21 Forces on an Electron Beam
A beam of electrons in bent in a circle by large Helmholtz coils.
[Current Condition: Good]

### 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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

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. Videos are at:
[Current Condition: OK, but it has suffered some abuse and will not function as well as in the video. It is on my list of things to improve.]

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.]
[Current Condition: Good]

### 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.]
[Current Condition: OK]

With no current: With current:

## 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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

### 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.]
[Current Condition: Good]

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.]
[Current Condition: Good]

5K20.25 Eddy Current TubesA strong magnet is dropped in plexiglas and copper tubes. In copper, the fall takes several seconds - even though the ball never touches the sides of the tube!
[Setup time: 5 mins.]
[Current Condition: Good]

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]
[Current Condition: Good]

Available Accessories:

An aluminum can is arranged in an AC magnetic field. When a phase modulation is introduced by the presence of another conductor, the can spins.
[Set-Up Time: 10 min.]
[Current Condition: Good]

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.]
[Current Condition: broken until power supply can be replaced]

some more dramatic discharges:

### 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.]
[Current Condition: Good]

### 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.]
[Current Condition: Good]

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)
[Current Condition: OK]

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)
[Current Condition: OK]

Front View: Back View:

Side View: Projection on Wall:

## 5L - AC Circuits

### 20. RLC Circuits - AC

5L20.10 RLC, RC, RL CircuitsConnect an inductor, capacitor, and resistor mounted on a wooden board. Connect in series with a function generator and measure across the resistor with an oscilloscope. As the function generator sweeps over the resonance, the waveform grows and shrinks on the scope. Or, connect L and C in parallel to show a resonance dip. Or use RL or RC alone to show monotonic frequency dependence and find f3dB points.
[Setup time: 15 mins.]
[Current Condition: Good]

## 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.]
[Current Condition: Good]

5M20.10 Gaseous Discharge Tubes
Six discharge tubes with successively smaller levels of vacuum are excited with the Tesla coil. Show Crookes dark space, negative glow, glass phosphoresence.
[Setup time: 5 min.]
[Current Condition: Unknown]

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.]
[Current Condition: Good]

Without Magnet:

With Magnet:

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.]
[Current Condition: Good]

### 10. Transmission Lines and Antennas

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.]
[Current Condition: OK]

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]
[Current Condition: Unknown]

### 20. Tesla Coil

5N20.1 Tesla Coil
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]
[Current Condition: Good]

5N20.40 Tesla Coil
Large Tesla Coil- draws very large/long sparks
Videos are available at:
[Current Condition: Good]

5N20.50 Tesla Coil-Discharge through bulb
Large Tesla Coil- light a fluorescent bulb in the vicinity of the coil.