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 sinosoidal current,the average power would be as follows:
Vef= Vmax/√2
















4.4.TRANSFORMERS:
Transformers consist of two windings made of cooper wire.If we apply an alternating current to one of them(V1), it will produce a certain voltage in the other (V2) the value will depend on the number of times that the cooper wire has been wrapped around each winding,represented as N1 and N2:

V1/V2=N1/N2.