A sine wave represents graphically the voltage of the electric current, where we can represent both the voltage of the electric current in direct current, and in alternating current.

**The waveform**

The alternating current is generated by different methods. The most used are the rotary mechanics, or alternators of the electric coils.

The most common waveforms are:

- the senoidal,
- the square,
- the triangular,
- the sawtooth

All are presented in different types very varied.

**Properties of a sine wave**

**1 Statement**

A disturbance along a string is described by the equation

with *x* and *y* measured in centimeters and *t* in seconds.

For this wave, find its amplitude, angular frequency, period, wave number, wavelength and velocity of propagation.

**2 Solution**

This function is a traveling wave corresponding to the general form

that, by itself of the form *f* ( *x* – *v t* ) is clearly a solution of the wave equation.

**2.1 Amplitude**

The amplitude of this wave, A, is the coefficient that multiplies the cosine. In our case

**2.2 Angular frequency**

The angular frequency, ω , is the coefficient that precedes the time in the cosine argument

**2.3 Period**

From the angular frequency we have the natural frequency and the period

**2.4 Wave number**

The wave number is the amount that multiplies x in the cosine argument

**2.5 Wavelength**

We calculate the wavelength from the wave number

**2.6 Speed of propagation**

The speed of advance of the wave is equal to

Summing up we can say that a sine wave of alternating electric current is bidirectional with respect to time (with positive and negative values) and the mathematical sinusoid that normally draws can be expressed as:

A ( t ) = Am a x⋅ s i n ( 2 π⋅ f⋅ t )