Home |
Search |
Today's Posts |
#11
![]() |
|||
|
|||
![]()
Roger wrote:
By my using the words 'power' "storage factor", you got my point, hence the reaction. Before dismissing the concept of "storing power", consider that when discussing a transmission line, it could be a useful description. As you know, power is energy delivered over a time period. No, it's the rate of energy delivery or movement, which is not quite the same thing. It always carries a time dimension having beginning and end. Power(watt) =v*i/(unit time) = 1 joule/second. Sorry, you've got this wrong. One watt is indeed one joule/second, but P(t) = v(t) * i(t), period. Energy is the integral of P(t) dt. Power is the time derivative of energy, or dE(t)/dt where E is the energy. You could as reasonably say that energy always "carries a time dimension". After all, one joule = 1 watt-second. In the example you give of charging a capacitor, the time dimension is lost, so you are correct that only energy is conserved. Power is lost. Sorry, I don't understand that. With a transmission line, we have an entirely different case. Here power is conserved because the time information is maintained. Power is stored on the line during the period it resides on the line. For example, we excite the line at one end and some time period later find that power is delivered to some destination. During the time period that the power was on the line, the information that defines the energy distribution over time has been preserved. Ok, let's test this. Please tell me exactly how many watts are stored on the line of the second analysis (where the perfect source is in series with a 150 ohm resistor). Next, tell me how many watts will come out of the line if we quickly disconnect the perfect source and source resistance and replace it with: A: A 50 ohm resistor, or B: A 150 ohm resistor If power is stored, we implicitly store energy. Energy is v*i measured in joules without a time factor. No, Energy is not v*i. Power is v*i. Energy is the time integral of v*i. Power is not stored; energy is. Obviously we store energy on a transmission line when we store power. I guess it would be obvious if you believe you can store power. But before going further, please demonstrate what you mean by calculating how many watts of power are stored on the example line. I showed exactly how many joules of energy were stored, you can show how many watts of power. So if in the future, I use the term "power storage", please take it to mean that energy distributed over time is under consideration. I'm afraid I'm not very good at translating what people mean when they say something else. Why not call energy storage "energy storage", power "power", and energy "energy"? Then I and hopefully other readers will know what you mean. The MKSA unit of power is the watt, and of energy, the joule. The two are no more the same than speed and distance, or charge and current. I hope the term might be useful to you as well. No, I have enough trouble communicating when I take great care with my terminology. The last thing I need is to be saying something which means something else -- or means nothing at all. When I mean energy storage, I'll say "energy storage", thank you. Roy Lewallen, W7EL |
Thread Tools | Search this Thread |
Display Modes | |
|
|
![]() |
||||
Thread | Forum | |||
Standing Wave Phase | Antenna | |||
Standing wave on feeders | Antenna | |||
Dipole with standing wave - what happens to reflected wave? | Antenna | |||
Newbie ?: I've Built A Simple 1/4 Wave Dipole for 2 Mtrs. Could IMake a1/2 Wave? | Homebrew | |||
What is a traveling-wave antenna? | Antenna |