What it shows: Long before the time of Copernicus, the Greek astronomer Claudius Ptolemy created a model of all the planets' observed celestial motions. The model involved combinations of perfect circles rotating with uniform speed. Ptolemy explained the apparent "looping motion" of the planets by placing the center of one rotating circle, called the epicycle, which carried the planet, on another rotating circle, called the deferent, so that together the motions of the two circles produced the observed looping motion of the planet. Moreover, the...
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...
Simulation of atmospheric scattering and polarization of sunlight using slide projector and aquarium containing milky water.
What it shows:
Unpolarized light passing through a fluid is scattered; the scattered light being partially or completely plane polarized. For scattering by particles of comparable size to the wavelength of the light, this process is called Rayleigh scattering. The wavelength dependence of this type of scattering is responsible for blue skies and red sunsets.
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...
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....
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.