4. TYPES OF CURRENT

4.1.Direct current

Between the terminals of a battery there is a continuous stable flow of energy. This is called direct current. In the same way if we connect a light bulb to a battery the electrons always flow in the same direction with the same current.

4.2.Alternating current

The flow of electrons changes direction 50 times every second as if the positive and negative poles of the socket were constantly changing places. In addition the electric current is not always the same.
The variation of any electrical parameter over a period of time is an electrical signal.
The tension or voltage of domestic electricity is an alternating signal because it alternates between positive and negative values. Its waveform is also sinusoidal with a smooth regular shape.



4.3.The efficiency of alternating current

The average power of alternating current is equal to the direct current that is needed to produce the same effect. In the case of an alternating sinusoidal current the average power would be as follows:

V ef =V max / square root of 2

4.4. Transformers

There is an important difference between alternating and direct current. Alternating can be increased or decreased by a transformer. this allows us to transfer electrical energy at very high voltages and over hundred kilometres, without losing any of the energy as heat.

THEIR SYMBOL IS: