Resources Services Physics Library Physics Links Lecture Demonstrations

Lecture Demonstrations
 Index Mechanics Fluid Mechanics Oscillations and Waves Electricity and Magnetism Thermodynamics Optics Modern Physics Video Astronomy What's New! Equipment
 What's New! View Printable Version

1H10.20 Fan Cart with Sail
A fan is mounted on a cart. First show that the fan propels the cart; then add a sail in front of the fan.
[Set-Up Time: 5 min.]

1L20.10 Orbits on a membrane
A large weight makes a depression at the center of a rubber membrane. Steel balls can be rolled around to show orbits.
[Setup time: 10 mins.]
[Current Condition: good- found a working membrane and stand!]

2B30.70 Vacuum Bazooka
A ping pong ball is sealed in a long evacuated pipe. When the seal on one end is broken, atmosphere propels the ball through the other end and through a soda can. This demo can be also set up with a motion sensor to calculate final muzzle velocity.
[Set-Up Time: 10 min.; with motion sensor 20 min.]
[Current Condition: good- fixed!]
video at:

2B60.60 Hydraulic Ram (Water Hammer)
A large quantity of water falling a small height pumps a small quantity of water a large height. The action is accomplished by creating a backward-propagating shock wave in the water about once per second. This demo is very entertaining.
[Set-Up Time: 10 min.]

3A60.2 Forced Mechanical Oscillator
THE OLD VERSION SEEN HERE IS BROKEN:
Side View: Front View: Back View:

The new version is bascially good to go, but it has some weird behaviors at around half speed (slow and fast work well though):

The frequency of a driving force on a spring can be varied to above, below, and (watch out!) at resonance. A mass hangs at the bottom of the spring, and it can be suspended in water to show the effect of damping.
[Set-Up Time: 15 min.]
[Current Condition: OK]

3A95.50 Double Pendula
Two double pendula are set up on a stand. No matter how close the initial conditions, their behavior will always diverge. The pendula keep swinging for several minutes.
[Setup time: 5 mins.]

4F10.10 Unmixing
Glycerine between two concentric cylinders is injected with a pattern of dye. When the inner cylinder is rotated, the pattern disappears, but when the turning is reversed the pattern re-appears! A very dramatic demonstration of the role of time and randomization in entropy. Also good for discussion of coutte flow/reynolds number.
[Setup time: 30 min.]
[Current Condition: Somewhat broken- needs advanced notice for attempted run]

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

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.]

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: Good]

some more dramatic discharges:

5L20.10 RLC, RC, RL Circuits Connect 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.]

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.]

6A44.? Bucket of Light
A laser beam follows the arc of a stream of water, and is not "released" until it reaches the collection bucket.
[Set-Up Time: 15 min.]

A white tile with a black circle on it is heated in a furnace until glowing. The black circle glows brighter than the surrounding tile.
[Set-Up Time: 30 min.]

Polarized laser light passes through a solenoid filled with toluene. When the solenoid is turned on, the polarization of the outgoing beam is rotated proportionally to the strength of the magnetic field.
[Setup time: 15 mins.]

7A60.50 Bragg diffraction with microwaves - improved apparatus
X-ray crystallography scaled up to centimeter wavelengths. The microwave source and detector are constrained to the same angle of incidence, which can been easily read off the device. The detector is attached to an audio speaker, through which the detected amplitude can be heard. As the beam angle is varied, or the crystal is rotated, distinct peaks are audible. A cubic crystal is currently available; different structures can be made upon request.
[Setup time: 10 mins.]

7B11.17/21 Absorption Spectra
Two lamps show different absorption phenomena. In one bulb, neodymium oxide in the glass absorbs a band in the yellow; in the other, sodium vapor around the bulb absorbs the yellow spectral line. Students observe the spectra through diffraction glasses.
[Set-Up Time: 5 min.]