# Practical Electronics/Sources

Sources that provide Voltage or Current to provide electricity for electrical devices to operate.

## Voltage Sources

There are two Voltage Sources generally used in any applications namely AC and DC Voltage Source:

### DC Electricity

DC stands for Direct Current . Voltage source that has constant voltage that does not change with time and can be expressed mathematically

v = V

DC Voltage sources are found in Batteries,

### AC Electricity

AC stands for Alternating Current . Voltage source that has current amplitude varies sinusoidally with time and can be expressed mathematically

v = Vp Sin wt
Vp The highest value of the voltage also called Peak Voltage measured in Volt (v)
t - time measured in second (s)
w - Angular Frequency . w = 2πf = $\frac{2\pi}{t}$

AC Voltage source are generated from AC generators.

## Current Sources

Current sources act in a similar manner to voltage sources, except that they try and maintain a constant current. Current sources are mainly constant current devices, meaning that they have a set value that they try and maintain, but also exist as variable devices, such as in transistor models.