# Category: Physics

## Subatomic particles

The standard model of particle physics is used to explain and order subatomic particles. Fermions Particles which join together to make up all the matter we see There are two main groups: quarks and...

## Special relativity

Inertial reference frame Motion of an object is typically described relative to a reference frame If the reference frame does not accelerate, and is therefore stopped or moving at a constant speed, it is...

## Resonance and standing waves

Forced oscillation Produced when an external periodic driving force vibrates a system The system will vibrate at the same frequency as the applied force The system will continue to vibrate as force is applied...

## Superposition and interference

Superposition Principle of superposition: when two or more waves meet at a point, the resultant displacement is the sum of the displacements of the individual waves. A wave can be represented by a series...

## Refraction and diffraction

Refraction In 3AB, only qualitatively. Quantitatively is out of the syllabus. Refraction is the bending of a wave when it enters a medium with a different wave speed When light moves from a fast...

## Wave meeting boundaries

The way the wave is reflected on how the wave and boundary interact What happens at a boundary is called a boundary conditions Fixed boundary A wave reflecting from the fixed end of a...

## Reflection

Reflection Law of reflection: Angle of incidence = angle of reflection θi = θr This is measured from the normal Convex and concave mirror Convex mirrors diverge the reflected light rays so that it...

## Alternating current

AC current is produced by an AC voltage Typically sinusoidal Terminology Peak voltage – the max voltage Peak Current RMS voltage/current = max voltage/current divided by root 2

## Transformers

A transformer is used to raise and lower AC voltages As a result, it raises and lowers current, but not power (unless inefficient) It is simply two coils wrapped around a common soft iron...

## Back EMF

In the above figure, EMF applied produces a current in the rod Current interacts with field, producing a force to the right (F = IlB) Speed of rod (v) increases However, the rod is...