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Golf Ball Atmosphere

A model of molecular motion and pressure using practice golf balls.

What it shows:

The kinetic energy of gas molecules bouncing off a surface causes pressure.

Increasing the molecules' speeds increases the pressure and the volume of the gas.

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RC Time Constant

Charging and discharging of a 10µF capacitor with variable time constant.

What it shows:

The growth and decay of current in an RC circuit with a time constant chosen so that the charge and discharge is visible in real time.

How it works:

By choosing the values of resistance and capacitance, a time constant can be selected with a value in seconds. The time constant τ is given by

τ = RC

To obtain useful values, we chose three resistors 100K, 200K and 400K in series with a 10µF capacitor, giving time constants of...

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Hall Effect

What it shows:

When a magnetic field is applied perpendicular to a conductor carrying current, a potential difference is observed between points on opposite sides of the conductor. This happens because the magnetic field deflects the moving electrons (Lorentz force) to the edge of the conductor and the altered charge distribution generates a transverse electric field.

How it works:

The conductor is a small bar (11mm × 2mm × 2mm) of germanium (p-type?). Current (18 mA) is made to flow down the length of the bar by a 3 volt potential...

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α, β, γ, n Sources and Detection

What it shows:

Radiations originating from atomic and nuclear processes are classified into four types:

charged particulate radiation consisting of
1. heavy charged particles (α)
2. fast electrons (β)
uncharged radiation consisting of
3. electromagnetic radiation (γ, x-ray)
4. neutrons (n)

The interaction processes of each type of radiation explain their penetrability through matter, their difficulty or ease of detection, and their danger to biological organisms. The interactions of these radiations with matter are unique and the...

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Collapse of 55 Gallon Drum

Drum evacuated by vacuum pump; crushed by atmospheric bombardment.

What it shows:

With an air pressure of 105 Nm-2 at sea level, even a heavy duty oil drum will be crushed if it has nothing inside to balance the pressure.

How it works:

The screw cap on the drum is fitted with a vacuum pump connector. Simply turn on the pump and wait; it takes about 8 minutes to pump down, so you can carry on with what you were doing interrupted by various creaks and bangs as the drum's side walls begin to give....

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Weighing Moles

Several samples are weighed on the balance; each is a mole.

The electronic scales are set up in front of the video camera. In a secondary container on the scale platform is a cube of lead weighing 208 g., 18 g of water in a bottle with an empty bottle for tare, and 200.6 g of mercury in a bottle with an empty bottle for tare.

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