Electrical Engineering ⇒ Topic : Types of Electric Current

Types of Electric Current

The electric current may be classified into three main classes: (i) steady current (ii) varying current and (iii) alternating current.

(i) Steady current. When the magnitude of current does not change with time, it is called a steady current Fig.(a) shows the graph between steady current and time. Note that value of current remains the same as the time changes. The current provided by a battery is almost a steady current (d.c.).

                                                                       figure (a)

(ii) Varying current. When the magnitude of current changes with time, it is called a varying current. Fig. (b) shows the graph between varying cun-ent and time. Note that value of current varies with time

                                                                      figure (b)

(iii) Alternating current. An alternating current is one whose magnitude changes continuously with time and direction changes periodically. Due to technical and economical reasons, we produce alternating currents that have sine waveform (or cosine waveform) as shown in Fig. (c). It is called alternating current because current flows in alternate directions in the circuit, i.e., from 0 to T/2 second (T is the time period of the wave) in one direction and from T/2 to T second in the opposite direction. The current provided by an a.c. generator is alternating cun-ent that has sine (or cosine) waveform

                                                                          figure (c)