Harvard Natural Sciences Lecture Demonstrations

Mechanical Linear Amplifier

What it shows:

One falling domino knocks down two, which in turn knock down three, etc. Use it to model cascade signaling.

How it works:

Twenty five rows of dominoes are set up in front of the first domino. Each successive row is comprised of one additional domino, e.g. the 2nd row has two, the 3rd row three, ... the 25th row has twenty five. A total of 325 dominoes get knocked down in a couple of seconds after the 1st one falls.

The action can be contrasted to a second board which has 11 rows of 30 tiles each, for a total of...

Electrostatic Shielding

How does shielding work? Is it a two-way street and work both ways? Can electric fields not penetrate metals? What's going on? This sequence of demonstrations addresses these questions.... Read more about Electrostatic Shielding

Slit Diffraction

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What it shows:

A liquid can be taken to a temperature below its freezing point if it is cooled slowly and there are no nucleation sites for crystallization to begin. In this demonstration you can create a flask of liquid water at below 0°C that, when 'seeded' by the introduction of a nucleation site (in this case dry ice) will be instantaneously frozen.

How it works:

This is pretty much described in Setting it Up.

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What it shows:

A 2000 μF capacitor is discharged by a carbon steel wire. The surge of current literally vaporizes the wire and it explodes into a spectacular arc of sparks that span the front of the lecture hall.

How it works:

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Edge Diffraction

What it shows:

A point light source will produce seemingly sharp shadows which turn out to be not at all sharp when viewed under magnification. Narrow interference bands are seen within the shadow of a straight edge while more complicated shapes yield more complicated interference bands and striations.

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What it shows:

This is a free-fall-from-rest experiment in which an apple (or any other object of comparable size) is dropped from the lecture hall ceiling into a catching bucket on the floor. By measuring the (1) distance and (2) duration of the fall, an accurate (± 0.022%) determination of the acceleration due to gravity can be made:

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What it shows:

It's impossible to magnetically levitate an object with static magnetic fields. However, it's posible to levitate a magnet with another hand-held magnet by taking advantage of eddy currents.

How it works:

A rectangular block of copper (6"×6"×2") is stacked on top of another one (6"×6"×1"). They are separated by 1" plastic spacers. A rectangular bar magnet (2"×2"×½") is placed in the space between them. When a second magnet is lowered from above, the two magnets attact each other. However, rather than "jumping up"...

Harvard Natural Sciences Lecture Demonstrations

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Key to Catalog Listings

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