Question

What is meant by one cycle of a.c.?
A. Going from zero to +maximum.
B. Going from +maximum to zero.
C. Going from zero to -maximum and -maximum to zero.
D. All the three mentioned above combined together in the same order.

Answer 1

Hint: The waveform of alternating current (A.C.) is sinusoidal in nature. So, draw a sinusoidal waveform having one positive half cycle and a negative half cycle. Its direction and magnitude changes after every half cycle with respect to time. From the waveform, we can infer what is meant by one cycle of A.C.

Complete answer:
A.C. means alternating current. Alternating current is defined as an electric current that periodically reverses its direction of flow. When a waveform reaches a complete set of positive and negative values it is called one cycle. Waveform for alternating current is given below.

From the above waveform, we can inform that the wave goes from zero to + maximum and then from + maximum to zero. Then, it goes from zero to -maximum and again from -maximum to zero. This forms one cycle of alternating current i.e. A.C.
So, all the three mentioned above combined together in the same order.

So, the correct answer is “Option D”.

Note:
Students must remember that a complete cycle may not have 360° of the waveforms. But it must have one positive and one negative half cycle. One cycle corresponds to an angular measure of 360°. The mean or average value of alternating current is zero because it contains one negative and one positive half cycle of the physical quantity and they get cancelled out. AC current is different from DC because in DC, electric current flows in one direction.