AC and DC: Electrically speaking

[lionkingcmsl]

Some idle musing on the train ride in this morning led me to the conclusion that the terms AC and DC are misnomers.

We are taught they they stand for Alternating Current and Direct Current, but when they show graphical representations of said currents they show the voltage waveforms. AC normally shows a nice sine wave, while DC's voltage is at a constant level.

Being you can't have negative current; though it may change direction, the terms should be AV: Alternating Voltage and CV: Constant Voltage. I feel that this more accurately describes what is happening. So that U.S. standard home power would be 120AV and a power supply to a IC board would be labeled as +5CV

I know that I won't change 150+ years of electrical teaching and dogma, but this is what I think of these terms.

Thoughts?

Comments

[kamiten.livejournal.com]

I personally don't see the problem with the naming. Alternating current flows back and forth, direct current flows only one way.

I understand what you're trying to say about not being able to have negative current. Amps are amps after all. But like voltage there is an argument to be made that negative amps do exist, and merely represent the amplitude at which current is flowing from positive to negative as opposed to flowing from negative to positive.

[thefoxaroo.livejournal.com]

Respect!! :D I like open minds, and people willing to challenge things that they grew up with and ask "does it need to be this way?"

I used to be interested in the nature of electricity when I was younger. I've lost much of the fascination, but can still recall bits of terminology.

IIRC correctly, when current passes through a transformer the wattage remains constant but the ratio of voltage and amperage is adjusted. Something about higher voltages being easier to transmit across a long distance (am I correct so far). If so, when you adjust the power setting on an appliance, for example the control unit on a model train set, are you adjusting the voltage, amperage or both being the wattage? If it's the voltage being adjusted, then would this affect your definitions?

I started typing a question about static electricity, but the electrons in my brain are too worn out this evening.

[lowen-kind.livejournal.com]

You are correct with higher voltages being easier to transmit over longer distances: that is the reason for "high tension" lines running across the landscape.

As for the throttle on a model railroad you are adjusting the voltage; the amperage doesn't change. In fact some of the better packs, until the advent of transistorized power packs, and most of the tinplate packs (Lionel, Marx, American Flyer) actually use variable transformers for voltage regulation.

[(Anonymous)]

Thanks. Given that there are situations where the voltage needs to be varied, would the definition of Constant Voltage still be applicable in circuitry?

[lowen-kind.livejournal.com]

Yes, the definition of "Constant Voltage" would still apply if you change the voltage. The term "Constant Voltage" means that the voltage doesn't change from the stated value, allowing for normal power supply ripple and electrical noise.

So a power supply may supply +12CV and a voltage regulator might change that to +5CV.