In the today’s world electricity is most important next to the oxygen in the human. When the electricity was invented many changes have taken place over the years. Dark planet turned into a planet of lights. In fact, it made life so simple in all circumstances. All the devices, industries, offices, houses, technology, computers run on electricity. Here energy will be in two forms, i.e. alternating current (AC) and direct current (DC). Regarding these currents and the difference between AC and DC will be discussed in detail, its basic function and uses of it. Its properties are also discussed in a tabular column.

Alternating current is defined as the flow of charge that changes direction periodically. The result obtained will be, the voltage level also reverses along with the current. Basically, AC is used to deliver power to industries, houses, office buildings, etc.

AC is produced by using called an alternator. It is designed to produce alternating current. Inside of a magnetic field, a loop of wire is spun, from which induced current will flow along the wire. Here the rotation of the wire may come from any no of means i.e. from, a steam turbine, flowing water, a wind turbine and so on. This is because of the wire spins and enters into different magnetic polarity periodically, the current and voltage alternate in the wire.

From this, the generated current can be of many waveforms like sine, square and triangle. But in most of the cases, the sine wave is preferred because it is easy to generate and calculations can be done with ease. However, the rest of the wave requires an additional device to convert them into respective waveforms or the shape of the equipment has to be changed and the calculations will be too difficult. Description of Sine waveform is discussed below.

If you were to connect an AC source and a DC source in parallel, the resulting waveform will be a level shifted AC waveform. Imagine having a sine wave of peak current amplitude of 10A. The circuit swings between +10A and -10A. If a DC current source of 10A is connected to the system, the circuit will oscillate between +20A and 0A, with the center line located at 10A.

In practice, we do not usually mix AC sources from household sockets and DC sources. (e.g. connecting positive to live and negative to neutral). Special protection circuits are needed to prevent the equipments from malfunctioning due to the resulting current. However, the mixing of AC and DC signals have other applications, such as carrying power over an ethernet cable from the server to a wireless router, or to power up remote audio equipments. In fact, experiments can be done in the lab using properly controlled AC signal generator and a DC source, and the results can be observed directly via an oscilloscope.

Nonetheless, just to answer your question, the voltage will retain the same sinosoidal waveform, but will be offset by a certain amount determined by your DC source.

Consider the image above, the green line shows the signal with offset. This may be a small voltage, but I assure you, the characteristics stays the same when scaled up to a larger voltage/current.

**Just for your information the term "Mix" has totally different meaning when it comes to electrical signals. Signal mixing implies multiplication of signal. If an AC signal is "mixed" with a DC signal, it will simply increase in magnitude proportional to the DC signal applied. This means that the sinosoid will be stretched vertically. Just so you know. Google "Signal Mixing" for more information.**