# Physics 1

meh

• Created by: DJackson
• Created on: 12-05-10 17:53

## Atoms

Atoms

· X is the element name.

· Z is the Proton or Atomic Number

· A is the Nucleon or Mass number.

· The charge is there for ions.

The Nucleus is composed of Neutrons and Protons which each have a mass of about 1.

Electrons have a mass of about 1/1800th of the others but a charge of negative 1.

The Nucleus is very dense.

Diameter of an atom = 10-10m. Diameter of Nucleus = 10-15m.

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## Electrostatics

Opposites Attract and Like Charges repel

Water is ionized because the Oxygen Nucleus is slightly negative and so is attracted to a charge.

Electric charge spreads evenly because it repels one another. This builds up voltage and can spark

Conductors have loose electrons, insulators don’t have De-localised electrons.

Semi-conductors become conductors when the bonds are broken with enough energy.

Charging with friction is called Tribo-charging.

Afterwards Insulators can gain electrons.

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## Magnets

There are two sorts of magnets: Electromagnets and Permanent magnets.

Permanent magnets are Nickel, Cobalt or Iron. Each Iron Atom has a magnetic field and when you rub it they align.

In a demagnetized magnet the domains are small and random. In a magnetised magnet they all point in a prevailing direction.

Domains are broken by heat or dropping. Steel is a hard Magnet because the domains are hard both to form and to break.

We can tell the direction of a magnetic field around an object by using the Right Hand thumb rule. Our thumb always points north when we follow conventional current.

Electro Magnets can be strengthened with 1.) Coil Density 2.) Stronger current. 3.) An iron core than isn’t already a magnet.

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## Waves

A wave is a periodic oscillation travelling through a medium.

Transverse: disturbance is perpendicular to wave travel. Longitudinal is perpendicular to wave travel.

Wavelength: Symbol: Lambda, Unit: Metres. This is the distance between 2 identical points on a wave.

Amplitude: Symbol: A, Unit: Metres. Maximum displacement from equilibrium.

Time period: Symbol: T, Unit: Seconds. The time taken for 1 complete cycle.

Frequency: Symbol: f, Unit: Hertz. Cycle of waves passing per second.

Wave speed: symbol: V, Unit: m/s. Speed of a point on the wave form.

Speed is distance over time or SIDOT or V=f lambda.

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