AC Half Cycles: Positive vs Negative

In summary: Figure 1: The waveform of alternating current. The positive and negative half cycles are the same size, and there is no pulsing. When V and I are in-phase, V*I is positive.
  • #1
M.Kalai vanan
32
0
what does the positive and negative half cycles in an ac represent?
 
Engineering news on Phys.org
  • #2
M.Kalai vanan said:
what does the positive and negative half cycles in an ac represent?

The direction of the current. That's why it's called ALTERNATING current.
 
  • #3
What does the C in AC stand for?
 
  • #4
I gather you're referring to a waveform?
It's a graph of volts versus time.
Traditionally horizontal axis is time; vertical is voltage with positive up and negative down.
 
  • #5
Personally I never liked the "C" - because power requires voltage AND current. In AC BOTH the voltage and current change polarity - so (typically) the power is always flowing in one direction.
 
  • #6
M.Kalai vanan said:
what does the positive and negative half cycles in an ac represent?
Positive and negative cycles represent the direction of the alternating current.AC reverses its direction many times in a second.Number of times it changes its direction in a second is measured as frequency.Go through the Alternating current for more information..
 
  • #7
Windadct said:
Personally I never liked the "C" - because power requires voltage AND current. In AC BOTH the voltage and current change polarity - so (typically) the power is always flowing in one direction.
Except for the special case of the load being purely resistive, the power in AC does alternate with each positive pulse followed by a smaller negative pulse to deliver an average power that is positive.
 
  • #8
NascentOxygen said:
Except for the special case of the load being purely resistive, the power in AC does alternate with each positive pulse followed by a smaller negative pulse to deliver an average power that is positive.

Sorry, but no. The positive and negative half cycles are the same size and there is no pulsing. When V and I are in-phase, V*I is positive when both V and I are positive, and V*I is positive when V and I are both negative. Look at the drawings in the Insight article.
https://www.physicsforums.com/insights/ac-power-analysis-part-1-basics/
 
  • #9
anorlunda said:
Sorry, but no. The positive and negative half cycles are the same size and there is no pulsing. When V and I are in-phase, V*I is positive when both V and I are positive, and V*I is positive when V and I are both negative. Look at the drawings in the Insight article.
https://www.physicsforums.com/insights/ac-power-analysis-part-1-basics/
Maybe you didn't understand what I wrote?

That's a useful article, including this figure which neatly illustrates the general case I describe:

45.gif
 
Last edited:
  • Like
Likes anorlunda

1. What is an AC half cycle?

An AC half cycle refers to one half of a complete alternating current (AC) waveform. In other words, it is the amount of time it takes for the current to go from its peak value to zero, and then back to its peak value in the opposite direction.

2. What is the difference between positive and negative AC half cycles?

The main difference between positive and negative AC half cycles is the direction of the current flow. In a positive half cycle, the current flows in one direction (from the positive terminal to the negative terminal), while in a negative half cycle, the current flows in the opposite direction (from the negative terminal to the positive terminal).

3. How does the direction of AC half cycles affect electrical devices?

The direction of AC half cycles can affect electrical devices in different ways. For example, some devices may only work with positive half cycles, while others may only work with negative half cycles. Additionally, the direction of AC half cycles can determine the direction of rotation in motors and the brightness of light bulbs.

4. Can AC half cycles be converted from positive to negative or vice versa?

Yes, AC half cycles can be converted from positive to negative or vice versa using a device called a rectifier. A rectifier converts AC into DC (direct current) by allowing only one direction of current flow, effectively changing the direction of the half cycles.

5. Why are positive and negative AC half cycles important?

Positive and negative AC half cycles are important because they allow for the efficient transmission of electricity. By alternating the direction of the current flow, AC can be transmitted over long distances without significant power loss. Additionally, the direction of AC half cycles is important for the proper functioning of many electrical devices.

Similar threads

AC Hipot Test on MOSFET: Can It Be Done?
    • Electrical Engineering
Replies
16
Views
2K
How do I properly connect a bench power supply to a pulse generator for testing?
    • Electrical Engineering
Replies
19
Views
1K
Alternator torque when connected to a phase-shifted AC source
    • Electrical Engineering
Replies
3
Views
546
Equation that describes positive/negative feedback
    • Electrical Engineering
Replies
20
Views
973
AC current through AC equipment
    • Electrical Engineering
Replies
14
Views
2K
Resistive heating power AC vs rectified AC/DC
    • Electrical Engineering
Replies
10
Views
2K
Can LCL Filter Convert AC to DC for Half Bridge Section?
    • Electrical Engineering
2
Replies
39
Views
2K
Boost converter duty cycle in DCM
    • Electrical Engineering
Replies
23
Views
3K
Reducing AC inrush current in this setup
    • Electrical Engineering
Replies
15
Views
619
Query about the time average of an AC power supply
    • Electrical Engineering
Replies
2
Views
1K

Hot Threads

Recent Insights

Back
Top