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Old 12-21-2009, 02:04 PM
 
Location: Bradenton, Florida
27,236 posts, read 44,150,068 times
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It seems that they're trying to assume some sort of physical resistance, not electrical resistance--is necessary to generate the current.
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Old 12-21-2009, 02:12 PM
 
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Quote:
Originally Posted by TKramar View Post
It seems that they're trying to assume some sort of physical resistance, not electrical resistance--is necessary to generate the current.
I have no idea what they're talking about. Adding physical resistance would drain off some of the energy, wouldn't it? It seems rather basic to me. Add ten pounds of resistance to a generator and you will burn more gasoline in turning it. It seems counterintuitive. The less resistance, the faster the shaft turns, the greater the current produced, no?
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Old 12-21-2009, 02:23 PM
 
Location: Bradenton, Florida
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You would think so...they're claiming otherwise.

Even though I've worked as an electrician for the the world's finest navy--what do I know?
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Old 12-21-2009, 02:29 PM
 
9,742 posts, read 9,963,068 times
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Quote:
Originally Posted by TKramar View Post
You would think so...they're claiming otherwise.
It's nonsensical. My car adds over a ton of resistance to its generator. Where is all that electricity going?
Quote:
Even though I've worked as an electrician for the the world's finest navy--what do I know?
I'm an ex-Navy man myself, and my comments come from remembering things I learned in A school.
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Old 12-21-2009, 09:46 PM
 
Location: Hopewell New Jersey
1,397 posts, read 7,409,975 times
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Quote:
Originally Posted by TKramar View Post
You're already spinning those wheels. Ever hear of inducing current in a wire?
Your lack of understanding..even for an "electrician" is amazing..

BTW... I'll accept your experience as an "electrician" and raise you by my 35+ years as a research EE (microwave communication systems) and my degree in physics....yeah yeah I know...so what huh...

I will try to do this as briefly but as succinctly as I can in a short space.

Yes a loop(s) of wire turning within a magnetic field induces a current flow thru the wire. That's the basis of generators/alternators. But it doesn't come for free. If there is no electrical load on the generator then the only additional drag on the system is the frictional losses presented by the bearings, and the minor (insignificant) air turbulence losses of the rotating commutator/armature assembly. Both of those factors are NOT what we're trying to get thru to you however. If the generator is actually connected to an electrical load (as opposed to just free spinning) then an additional mechanical force (torque) will be required to turn the generator (shopping cart wheel in this case).

There are a few very simple experiments that you can do/observe to demonstrate what I'm trying to describe.

1: Given a running portable generator....such as you might find at a construction work site. Everything is running...the gas engine is say running at 2500 RPM and all is well. The generator pack is there to power a air compressor used to run various construction tools. Then the pressure regulator in the air compressor used by the nail guns/jack hammers etc kicks in. You will notice that the gas engine "loads" up and it's governor opens the engines throttle a bit in order to maintain the same RPM on the motor /generator set. Ask yourself why ?? The windings were all ready spinning at whatever rate they were...so why all of a sudden does the engine have to work harder just because the compressor kicked in.

2. Locate a small permanent magnet DC (battery) powered motor such as you might find in a child's toy (or a bedroom toy, for that matter. If you take the motor in hand and not connected to anything, ie..lead wires open to free space, you can spin the motor shaft easily with your fingers. Now if you take the leads and short them together (this represents a significant electrical load) you will find it's extremely difficult to turn the same shaft with your fingers. Again I ask...why...same mechanical setup..same bearings etc...

It's because when the wire/leads are shorted together you're actually driving current into a load instead of just free spinning the armature.



Beyond this I can't really help you...you may know the national electrical code book front to back but your understanding of some very basic principals of science is grossly lacking.


Just thought of another example you will be familiar with without having to do any "experiments".

3: Power tools....circular saw/radial arm saw etc. Most larger power tools nowadays have whats commonly called "dynamic braking". That's the effect that when you take your finger off the power button the cutting tool very quickly comes to a stop..as opposed to coasting along for 30 to 45 seconds. This feature is done of course for safety. This is how it works. When the tools is powered up the motor is connected to the line voltage and is running etc. When you release the hand trigger etc the motor is disconnected from the line source AND ( very important) the motors leads are connected together . ie...during the rapid slow down phase the motor is reverse connected and is now electrically configured as a generator. The motor (now a generator) leads are connected via the trigger release to a passive load which causes the spinning armature to slow much more rapidly than it would otherwise if just left to "coast". The quick reduction in rotating speed is due to the fact that the motor/generator now is connect to an electrical load and that electrical load requires a mechanical a input...( the rotating mass of the armature). No mechanical brakes etc are used.....

BTW...even diesel/electric locomotives use this same technique for braking and rely upon physical mechanical brakes very little.

Last edited by JBrown; 12-21-2009 at 11:01 PM..
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Old 12-21-2009, 10:57 PM
 
Location: Hopewell New Jersey
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4: I'm sure you've jumped a car at some time in your life.

Ever notice that the car giving the jump, idling along just fine, drops in rpm when you make the last connection to the car your jumping ?? Why is that ??

The car giving the jump was idling fine, the alternator was spinning merrily along etc..then you make the final connection and wow...the engine in the car giving the jump loads up (a drop in rpm)..

hint...now in addition to just spinning the armature in the alternator you're also connected to an electrical load which needs more mechanical power to produce the electricity to deliver to the dead car.


I suggest you get a copy of a high school science book...read the sections on electricity and magnetism. you should find it illuminating.

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Old 12-21-2009, 11:28 PM
 
Location: Southeast
4,296 posts, read 6,651,527 times
Reputation: 1457
Shopping carts takes quite a beating in the parking lots of the store, would hate to see what would happen if one of these was left out in the rain, they can't be cheap after all. Interesting concept, however, if there is added resistance to the cart wheels I can already see loads of problems.

Quote:
Originally Posted by chielgirl View Post
There are pages and pages of threads where you, and I'm certain others, have used the term "moonbat" - I have no desire or time to search each of them.

Obviously it's negative.
Says more than I need to know.
If you do not want to know, why did you ask what it meant?
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Old 12-22-2009, 02:04 AM
 
11,944 posts, read 13,856,655 times
Reputation: 2772
Why would anyone need a degree in microwaves communicating with one another? Why can't they just cook food minus the chit chat?
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Old 12-22-2009, 04:29 AM
 
Location: By the sea, by the sea, by the beautiful sea
66,559 posts, read 48,303,587 times
Reputation: 36728
Quote:
Originally Posted by nvxplorer View Post
I have no idea what they're talking about. Adding physical resistance would drain off some of the energy, wouldn't it? It seems rather basic to me. Add ten pounds of resistance to a generator and you will burn more gasoline in turning it. It seems counterintuitive. The less resistance, the faster the shaft turns, the greater the current produced, no?


IF generators produce electicity with no physical resistance, WHY does it take things like steam turbines to power them, why not just spin 'em up by hand? Generator is a misnomer, it doesn't generate electricity, it converts mechanical energy to electrical energy with (usually) some loss due to friction.
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Old 12-22-2009, 05:51 AM
 
Location: Hopewell New Jersey
1,397 posts, read 7,409,975 times
Reputation: 1047
harborlady

Each brand of popcorn has it's own unique accent depending upon it's region of origin. Learning the language of pops and sizzles is no small feat.




Last edited by JBrown; 12-22-2009 at 06:01 AM..
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