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Jumping Wire

What it shows:

A current carrying wire in a magnetic field experiences a force at right angles to both the field and current directions. The wire will jump up or down, depending upon the current direction.

How it works:

On a microscopic scale, the electrons in the wire experience a Lorentz force due to the magnetic field,



the force perpendicular to both field and velocity vector. On the...

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Continuous Spectrum

What it shows:

White light is shown, á la Newton's demonstration of dispersion by a prism, to be composed of a continuous spectrum of colors.

How it works:

A large brilliant spectrum is produced by using a 1 kW carbon arc light source 1 with adjustable slit, a "fast" f/0.9 imaging lens, 2 and a highly dispersive in-line prism. 3 The spectrum easily fills a two meter wide screen with vibrant colors. An alternative (more compact) setup consists of a Beseler slide projector 4 which...

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Collisional Broadening

What it shows:

Perturbation by colliding atoms in a high pressure gas result in the broadening of emission and absorption lines. This is clearly seen in the sodium D (589nm and 589.6nm) lines of a high pressure sodium lamp.

The broadening in frequency width is dependent upon the separation of the perturbing particles (Novotny 1973) by

∆ν ∝ r-n

With n=2 the broadening is due to the coulomb field of an ionized atom or electron; this is the linear Stark effect. With n=3 the interaction is between neutral atoms of the same type; this...

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Convection Cell

What it shows:

Hot fluid rises, cool fluid sinks. Here is a desktop convection cell modeling the processes in the atmosphere, oceans or stellar interiors.

How it works:

The currents are set up in rheoscopic fluid 1 (basically minute aluminum flakes in water) in a small 10×10×15cm glass tank. Half the base of the tank rests on a heater, the other on an aluminum block that acts as a heat sink. The rheoscopic fluid has a weird metallic sheen such that the bulk motion of fluid is clearly seen from the changing reflectivity....

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Smog in a Bottle

Nitrogen dioxide is produced by an electric discharge in air and, when sprayed with a water mist, produces acid rain.

What it shows:

Some of the most irritating and dangerous pollutants in our atmosphere are gases such as sulfur dioxide and nitrogen dioxide. Nitrogen dioxide is a deep orange-red gas that, together with smokelike particles, is responsible for the color of smog. In this demonstration, nitrogen dioxide is produced by an electric discharge in air and, when sprayed with a water mist, produces acid rain.

How it works:...

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Poiseuille's Law

What it shows

Poiseulle determined that the laminar flow rate of an incompressible fluid along a pipe is proportional to the fourth power of the pipe's radius. To test his idea, we'll show that you need sixteen tubes to pass as much water as one tube twice their diameter.

How it works

Poiseulle's law states that the flow rate Q is also dependant upon fluid viscosity η, pipe length L, and the pressure difference between the ends P by

...

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Uniform Acceleration

Glider acceleration by an inclined air track or by a falling weight/string attachment; large ballbearing rolling on PASCO track (with strings).

uniform acceleration

Reactionary Roadbed

Radio controlled car moves one way while road moves the other.

What it shows:

We tell our students that, when a car drives down the road, the road and the Earth move in the opposite direction, albeit imperceptibly. This demonstration is a realization of that concept, made possible (and perceptible) by the fact that the road is not attached to the Earth.

...

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