Generators

Just common sense think about it and it will be clear. It is too fundamental and one that need not be explained. At least in and engineering forum.

UD15

Ok, here's a big hint for you. What is the technical definition of work and how does it apply to what your motor that spins your generator? If you answer that question here, I'll help you to explain what is happening.

What kind of work do you do there? What educational background do you have?

If you don't know the answer to the question you are asking, do you really think you should be calling yourself "guru_88"? Usually the term guru is reserved for a person who is an expert among experts.

I agree with Redfred, I have guru status here but I am not an expert among experts. I achieved guru status because I won't go away...and posted enough times to activate it. I have my knowledge, experience and schooling but do not consider myself a guru, how about you 'guest'?

As to the original question, it takes work to generate electricity, but that electricity needs to be consumed before the greater resistance is placed on the windings of the generator. The greater the load the greater the resistance.

For example, if you are just using a small generator to power some shop lights the generator will hum along at a low idle, because not much electricity is being used. Now, if you fire up a large electric motor powered by the generator you will hear it bog down then rev up to handle the increased load placed on it by the electric motor's consumption.

Drew

My questions -- What kind of work do you do there? What educational background do you have? -- weren't intended to be critical. Those were just asked out of curiosity. I was curious what his job is there; I wondered why the boss was asking him that specific question.

I suppose my comment about calling himself 'guru_88' was a bit snarky. I suppose that was a bit uncalled for.

A "hands on" example I got as a kid, was a hand cranked generator in a display at the local museum, the crank was easy to turn until a switch was closed, completing a circuit to a light bulb, the crank then became much harder to turn.

The phenomena, it was explained, was due to the passage of a conductor driven by force (work) through static magnetic flux lines, unopposed, with no electrical load (work) in contrast to the passage of this conductor with it's own now induced magnetic field (a product of the load) which opposes the static magnetic field.

HI dear guru_88,

It seems to be dark from the first day of your job,,, please tell us what heppened next days?

awaiting ..............

I apologize for using the term flux lines in my attempt to simplify my explanation based on the timbre of the OP's question.

I hope his conception has not been damaged by my completely false statement.

:-) Sorry, I didn't mean to be rude. It just hit on a pet peeve of mine. A silly little compulsion to correct this concept that probably falls under some clinical diagnosis.

Fields lines are a good way to visualise the concepts, but it ends up hurting when you get further into the physics.

My apologies for snapping at the concept.

-Doug

You were not rude, These examples were used by the military to explain the function of flux gates in conjunction with directional heading information, three axis data for magnetic anomaly detection and helped me to grasp the concept. I did not venture into physics.

So in the case of a flux gate, is it the vector (if the gate is stationary) that influences the output?

Hello,

Speaking of back emf, I would like to share my thoughts...

As you said, the back emf is responsible for producing the counter force that makes moving the rotor more difficult... but isn't the rotating rotor is what responsible for producing the back emf in the first place..?

In other words, am I right when I say that the back emf 'works' to destroy itself ?

Yes, the two are directly related. The varying EM field causes the electrons to move and in return the movement of the electrons cause an opposing EM field to be realized. It is an effect of Relativity in relation to the moving electrons and makes a beautiful balance for conservation of energy. If this wasn't the case then free energy would be easy, but regrettably the universe would also rip itself apart almost instantaneously. I guess there are trade-offs with everything.

-Doug

Ok, but where do the electrons come from?

Drew

Minneapolis of course. They have an abundance. They've had a good seasonal harvest, too.

Now on a more serious angle, electrons appear to be one of the most fundamental elements of matter. While many additional electrons have propagated from beta particle decay releases that move an atom's nucleus up the periodic table, I believe that it is safe to say that they predominantly came from the initial big bang.

But in this more relevant case, the electrons are the outer valence electrons that are easily migrated in the conductive material. Since the circuit though must be considered a closed loop for migration to happen the electrons displaced get immediately (well nearly) replaced by electrons coming fro the other direction. Thus before any chemical reaction might occur the balanced neutrality returns.

But you knew this anyway.

Not really, I was thinking that is what happened, but wasn't sure. So that is why there needs to be a complete circuit for current to flow?

Drew

Yes, this is why a closed circuit must exist. For electron motion to happen without a closed circuit ionization must occur. Ionization requires much more energy per electron moved than in a closed circuit basis. Now additionally if you look at a periodic table, you will notice that all of the metals lie on the left side of the table and they have a few electrons in their outer valence shell.

The noble gasses all the way to the right have a completely filled outer shell. These elements are so electrically stable that they don't even make the partial attraction binds that make for cooler temperature phase states. So even the heavy radioactive element Radon is a gas at Standard Temperature and Pressure (STP aka room temp 1 atmosphere).

In contrast the elements just to the left of the noble gasses have a near complete shell. In there elemental form they then can be considered as having a hole (missing electron) in there outer shell even though adding an electron will mean making an ionized element. This is why any metal oxide though is considered an insulator and not a conductor.

Aha, now part of that I do remember from Chemistry!

Thanks for the clarification. I had never taken chemistry, even in high school so I was completely overwhelmed when I stepped into the deep end with General Chem 1 in college.

Thanks,

Drew

Current and torque are inter-related.

Elementary Dear! How fast can you run without any load on your shoulders? And, how fast can you run with some load on your shoulders? Definitely not at the same speed as with no load. Isn't it? The same analogy can be applied to machines as well.