# Electric voltage

Electronics is based on physics. The basic concepts here are voltage, current and resistance. We should start with that. The voltage is therefore a measure of the strength of electric charges. The voltage between two points of an electric circuit or electric field is the difference in electrostatic potential between these points. We measure voltage in volts. We use a voltmeter to measure the voltage. We always measure voltage between two points because it is a potential difference.

The voltage can be constant, variable, alternating. Why we use a given form of tension depends on the purpose, losses, efficiency and probably also safety. The difference between volatility and commutation is a question of waveform shape and its distribution along the axis. Voltage and current are inextricably linked concepts. If there is no voltage in the circuit, no current is flowing in it.

## Alternation

Periodic form of a signal with waveforms on both sides of the axis

 The current is represented as a shape, the signal can have different forms depending on how it is initiated.

If we give it a given periodic form, in which its value will alternately take a negative and a positive form, then we will call such a current alternating.

## Variability

The periodic form of a signal on one side of the axis

 However, if this form is periodic, but not commutative, then we can only speak of a periodic but a variable current. Such a signal is repeatable, but its amplitude waveform does not exceed the axis on the graph. The difference between a constant, alternating and alternating signal is important from the point of view of circuit design.

If a given form of a signal, be it a variable or an alternating one, should have a specific form, the task of various components and systems is to provide them with this target form in the simplest possible way.

## Peak frequency and voltage

Signal amplitudes and actual voltage

 In a house, we have alternating current with specific parameters, such as 230V and 50Hz frequency. This means that in 1 second there are 50 changes (alternations) from the peak value, then as it falls down, the axis is crossed at the zero point (more precisely across the equilibrium level) to reach the opposite value. These changes create an alternating current sinusoid. There may be a voltage in the network with a certain deviation, between 5 and 10%, depending on the characteristics of the supplied voltage and the installation itself that supports it. Therefore, assuming the maximum values, it is about 250V effective voltage. For a perfectly sinusoidal waveform, the peak value of the ac signals will be

`Umax = Usk * √2`

For a triangular waveform, this would be the first a square root of 2. For a square wave it will be 1. For an average outlet voltage, the peak voltage may be around 350-360V.

Note: Amplitude is the maximum deviation of the signal from the equilibrium level. Voltage amplitude is denoted as Um, and the current as Im. Finishing this topic, it is worth mentioning that the shape of the current waveform is sinusoidal because the generator core works in a circular motion, which is inseparable from the shape of the sinusoid.

Examples available at https://github.com/michalasobczak/simple_hpc/tree/master/SeriesPartOne