Question about power rating clickie.

[AUS]

Woah, looks like I missed a fair bit in this time zone while I was at work...

Yes I apologize for sabotaging the thread, I like people to understand things however I suspect this is becoming a debate of semantics rather than serving any educational purpose.

Cyparagon, your diagram shows the earth connected at the bottom of the circuit and the o'scope isn't earthed. You moved the common point of the circuit, the earth/ground of the circuit never moved.

Bionic-Badger makes a good point and is correct, in your example of the inverter, the lightglobe will be bright at both the +110V and -110V points and dimmest at the zero crossing point. As its polarity swings from + to - its AC. If it was all above the zero volts line there would be no flash at the bottom and it would be DC.

If it was DC there would be no peak below the line. You do actually understand that current in an AC circuit reverses direction every half cycle and each pole swaps from being + to negatively charged?

I did a diagram but I suspect you do actually understand but are just being pedantic and deliberately difficult in which case it would serve no real purpose other than continue to derail the thread

 

[Blord]

I don't mind if people get in depth of the theory. I was watching this thread with open mouth. Most of the information is way beyond my knowledge of electronic. But it is still interesting read.

 

[Cyparagon]

At which point it really isn't pulsed DC anymore is it?

That's my point, pulsed DC is AC, and DC superimposed.

Do you understand? If not, I need to move to Fourier transform. I'd rather you googled it first and asked about what you don't understand, though.

Cyparagon, your diagram shows the earth connected at the bottom of the circuit and the o'scope isn't earthed. You moved the common point of the circuit, the earth/ground of the circuit never moved.

See, THIS is the point you continue to miss.

ground. is. arbitrary.

Just to humor you:

You can be fckin' goofy and put it on the top if you want.

You do actually understand that current in an AC circuit reverses direction every half cycle and each pole swaps from being + to negatively charged?

Not always. That is a shallow understanding. It's like saying lasers are always monochromatic.

Please google Fourier transform.

 

[Bionic-Badger]

That's my point, pulsed DC is AC, and DC superimposed.

It's not Cyparagon. While you are describing frequency components on the DC signal, the electrons are not alternating with respect to ground (the original ground where the "DC" is defined).

The main problem with your argument is that you're changing the ground reference mid-discussion. Changing the ground reference implies that the signal you're describing is not the same as the original. This is as silly as stating that a battery supplies 1.5V (with an implied ground reference of the other terminal), and you jumping on me, telling me it's actually -200V because you've chosen some other arbitrary ground reference at that point in time. The ground reference needs to stay consistent if we are to describe the same signal and voltage potentials. This kind of ground reference changing is what causes people to fail in their EE homework problems.

Ground reference changes is what occurs when you pass a signal through a capacitor: now the ground reference has changed, and this is why you can produce AC by passing a signal with non-zero frequency components through a capacitor.

Do you understand? If not, I need to move to Fourier transform. I'd rather you googled it first and asked about what you don't understand, though.

It's nice that you want to cite your favorite transform as proof, but you need to understand how to interpret it. When you look at the spectrum of a signal do you see the zero-frequency component exceedingly large in value? If so, that component may dominate the signal to the point that remaining frequency components do not have amplitudes large enough to cross over zero.

When you change the ground potential, as you have been doing, the zero-frequency component of the spectrum is also changed. In essence, you're not talking about the same signal anymore. The spectrum also reflects this.

More importantly, just because you can take a Fourier transform of something and see frequency components does not imply the signal on a line is AC. Alternating current literally means the flow of current is moving back and forth. The voltage changes sign when power is delivered to the load. Power delivered to a load using DC, even with non-zero frequency components, does not change sign; the electrons may "slow down", so to speak, at the lower voltages, but they do not reverse direction--i.e. alternate.

I'd like to tie this back to the original discussion regarding switches. It is important to distinguish between "AC" and "DC" in fundamental terms because they affect, for example, how current gets "squelched" by the reverse flow of electrons. The higher frequency components of a DC power line are not going to facilitate this kind of physical interaction, and therefore you need to understand the type of signals you're dealing with.

See, THIS is the point you continue to miss.

ground. is. arbitrary.

Ground must stay consistent if we are to speak of the same signal. Do not change the goal-posts mid-discussion in an attempt to prove an erroneous point. That is the logical flaw in your argument.

I hope you're not doing this in your homework problems as well. Maintaining consistent ground references is essential to circuit analysis.

 

[Cyparagon]

Yes please, let's keep this on switches.

I'd like to tie this back to the original discussion regarding switches. It is important to distinguish between "AC" and "DC" in fundamental terms because they affect, for example, how current gets "squelched" by the reverse flow of electrons.

Just how it gets "squelched" by forcing the voltage to zero.

 

[Bionic-Badger]

I believe it has to do with both the reduced slope of the voltage transition (switching on a sine-ish wave instead of a harsh step function) as well as the "momentum" (for lack of a better term) of the fields in AC waveform (here's a nice visual representation with respect to wave rendering).

 

[Cyparagon]

Care to elaborate?