Electromagnetic Spear

What it shows:

Static 3-D stylized model of an electromagnetic wave, with two sets of sinusoidal fins at 90° representing the E and B fields.

How it works:

The wave packet model consists of a wooden spine with E and B fins of 1cm wooden dowels. A plastic arrowhead gives the spine a direction.

Figure 1. The Spear


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Sugar Syrups

What it shows:

Certain materials (sugar in this experiment) are optically active because the molecules themselves have a twist in them. When linearly polarized light passes through an optically active material, its direction of polarization is rotated. The angle of rotation depends on the thickness of the material and the wavelength of the light.


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Precession Globe

Globe pivoted so north pole can precess.

What it shows:

Due to the oblateness of the Earth, the gravitational force between the Earth and the Sun sets up a couple which causes the Earth's axis of rotation to precess. An adapted globe shows what is meant by precession.

How it works:

An old 8" (19cm) globe has been modified 1 to allow it to precess on its axis. A 23° cone is cut into the south pole, and a cone of metal supported by a metal equatorial ring has been inserted. This makes the globe bottom heavy (and...

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Ball on string orbits with increasing speed as string is shortened.

What it shows:

An object moving in a circular orbit of radius r has an angular momentum given by:

L = r × mv = mr2ω.

A simple way to show conservation of angular momentum is a ball on a string, whirled around your head. As you change the length of the string, the ball's orbital speed changes to conserve angular momentum.

How it works:

The orbiter consists of a meter length of cord with a wooden ball at one end and a wooden anchor at the other. The cord passes...

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OHP RLC Circuit

What It Shows

The current in a circuit consisting of a capacitor, inductor, and resistor will oscillate back and forth as the capacitor charges and discharges.

How It Works

The circuit layout is shown in the figure below. Initially the knife switch links the capacitor to the battery. Switching to complete the LRC circuit allows the capacitor to discharge. The current I in the circuit increases, as does the magneic field B inside the inductor. When the capacitor charge is zero, I and B are a maximum (the energy of the circuit is now stored in the inductor). As the...

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Wien's Displacement Law

Changes in the spectral intensity distribution of a hot tungsten filament are observed as the temperature is varied.


How It Works

A slide projector (Beseler Slide King II) with a 1kW lamp and adjustable lens is plugged into a Variac. The light from the projector passes through an inline...

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Moon Orbit Model

Mechanical model of Earth-Moon orbit around Sun.

What it shows:

A model to demonstrate the precession of the Moon's orbit relative to the ecliptic. It is useful for discussing the conditions necessary for the occurrence of an eclipse.

How it works:

A large aluminum disk represents the plane of the Moon's orbit about the Earth. The disk lies flush with the box surface it sits in; the plane of the box representing the Ecliptic. The Moon's own orbit is inclined at 5° to the ecliptic, and precesses with an 18 year period. You...

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Viscous Fluid

What it shows

For a body to reach terminal velocity when falling through a fluid, the drag force (given by Stoke's Law) coupled with the buoyant force (from Archimedes' principle) need to balance the falling object's weight. Leaving derivations to other great texts you end up with


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