Question

Average value of AC current in a half period may be :
A. Positive
B. Negative
C. Zero
D. None

Answer 1

Hint: In order to solve this problem we need to know that average value is always counted for half cycle and not full cycle since the value of full cycle is always zero.The alternating current is positive for the first half of the cycle and negative during the next half of the cycle, so the average value of ac over one cycle is zero.. But in the half period it is positive.

Complete answer:
Alternating current is an electrical current that regularly reverses direction and changes its magnitude constantly over time, in comparison to a direct current that flows only in one direction.
The value of the AC voltage is constantly shifting from zero to the positive peak, from zero to the negative peak, and back to zero again. The RMS value is the effective value of a variable voltage or current. It is the equivalent constant DC value which gives the same effect.
Average value is only counted for half a loop, not complete. Since the mean value over the complete duration of a sine wave is always zero. But for the half-cycle, its value is 0.637 times the peak value. So the value is positive.

So, the correct answer is in half period the average will be positive whereas in full period half is positive and half is negative so the average is zero in full period.

So, the correct answer is “Option A”.

Note:
When you get to solve such problems you need to have a brief knowledge of AC circuits that is the generation of voltage and the use of transformers and how it converts the not changing terms into the variables which repeated its value over a period of time is called time period. Knowing about these things will give you the right answer and will give you the right answer.