# Physics

Get flash to fully experience Pearltrees

## Heinrich Hertz: The Discovery of Radio Waves

The Discovery of Electromagnetic Radiation The most dramatic prediction of Maxwell's theory of electromagnetism, published in 1865, was the existence of electromagnetic waves moving at the speed of light, and the conclusion that light itself was just such a wave. This challenged experimentalists to generate and detect electromagnetic radiation using some form of electrical apparatus. The first clearly successful attempt was made by Heinrich Hertz in 1886. For his radio wave transmitter he used a high voltage induction coil, a condenser (capacitor, Leyden jar) and a spark gap - whose poles on either side are formed by spheres of 2 cm radius - to cause a spark discharge between the spark gap’s poles oscillating at a frequency determined by the values of the capacitor and the induction coil. This first radio waves transmitter is basically, what we call today, an LC oscillator.

## Electromagnetic waves

At this point in the course we'll move into optics. This might seem like a separate topic from electricity and magnetism, but optics is really a sub-topic of electricity and magnetism. This is because optics deals with the behavior of light, and light is one example of an electromagnetic wave. Light and other electromagnetic waves

## Circuit Simulator Applet

This java applet is an electronic circuit simulator. When the applet starts up you will see an animated schematic of a simple LRC circuit. The green color indicates positive voltage.

## members.iinet.net.au/~pterren/Can

An eddy current brake of a German ICE 3 in action. An eddy current brake , like a conventional friction brake , is responsible for slowing an object, such as a train or a roller coaster. However, unlike electro-mechanical brakes , which apply mechanical pressure on two separate objects, eddy current brakes slow an object by creating eddy currents through electromagnetic induction which create resistance, and in turn either heat or electricity.

## Eddy current brake

In the photograph, note that the coil on the left has fewer coils than that at right (the insets show close-ups). The sketch and circuit show a step-up transformer. To make a step-down transformer, one only has to put the source on the right and the load on the left. ( Important safety note : for a real transformer, you could only 'plug it in backwards' only after verifying that the voltage rating were appropriate.) So, how does s transformer work? The core (shaded) has high magnetic permeability (ie a material that forms a magnetic field much more easily than free space does, due to the orientation of atomic dipoles). The result is that the field is concentrated inside the core, and almost no field lines leave the core.

## Transformers

CHEMISTRY & PHYSICS

## Electronics Demonstrations

CAD software is commonly used for drafting architectural and engineering drawings and for making technical illustrations of any kind. If you are a professional associated with design or drafting or would just like to widen your knowledge about CAD applications, then you will find this section of informative and useful. CAD enables you to prepare fast and accurate drawings. It provides flexibility to change drawings with minimal effort. In recent years, many professionals have switched to CAD to enjoy the benefits of this precise and creative tool.

## Electricity and Magnetism

Electricity and Magnetism Timeline of Electricity and Magnetism - Our timeline guides you through the highlights of electricity and magnetism across the globe, from the first compasses in China to the invention of magnetic core computer memory at the Massachusetts Institute of Technology and beyond. Pioneers in Electricity and Magnetism - Ampere, Celsius, Kelvin, Hertz, Tesla: These terms are familiar to all science students. Behind them is a group of scientists who went down in history for their groundbreaking work in magnetism and electricity. Who were these brilliant inventors, physicists and chemists, and what lasting contributions did they make to their fields – and to our lives?
New Explanations, Alternate Mental Toolkit William J. Beaty Electrical Engineer, U. of Washington Jump down to Highly Recommended Books or Build-it Projects . What's the relation between Watts, Ohms, Amps, and Volts?