Electricity question

[opticalmace]

Evadman laid down some ownage.

 

[DrPizza]

Originally posted by: eelw
You still need to complete the circuit.

That took a lot of posts before it got posted...
It's weird that so many "Electrical Engineers" posted, yet didn't post the answer.
They didn't know?

 

[PurdueRy]

Originally posted by: DrPizza

Originally posted by: eelw
You still need to complete the circuit.

That took a lot of posts before it got posted...
It's weird that so many "Electrical Engineers" posted, yet didn't post the answer.
They didn't know?

Thats because, as many have pointed out, there IS a voltage there in the form of a potential difference. However, a DMM can only measure the voltage of a completed circuit. So you only need to complete the circuit if you want to use a DMM, however, theoretically, it can be measured without one.

Note: Most of us have specified that we are EE students, not EE's. Although from what I have seen, most of our comments have been correct.

 

[DrPizza]

wow, this has been a fun thread to read... I hope at the end of 2005, there's a category for "best e-penis fight" This is at least worthy of nomination.

Evadman, excellent post. Yes, neutral and ground are different, however, (and I think someone as well as you pointed it out) inside a house, the neutral and ground are identical - they are electrically connected at the breaker (or fuse) box for safety reasons. You could unsafely switch the ground wire and the neutral wire in every electrical outlet in the house if you wanted to, as long as the bare ground wire (which you're now using as neutral) wasn't touching anything metallic on its journey.

Also, I've seen plenty of "it has nothing to do with completing the circuit. "
Okay. Then, tell me *how* you can measure the potential difference of a battery without completing the circuit.
You can forget about answers "theoretically, I can take a voltmeter with infinite resistance and..." because that part of the theoretical is nonsense. The electrical resistance from one side of the universe to the other side of the universe is quite high, but not "infinite" So, "theoretically" , a voltmeter with infinite resistance is impossible...

Everyone seems to be expressing the same idea in two different ways. Yes, there is no potential difference between either end of the battery and the wall (or at least, not any appreciable potential difference). The potential difference in a battery is due to a chemical reaction, and the potential difference is from end to end. TuxDave's analogy was great. It's like saying how tall are you - it's in relation between your head and your feet. Not your head and some other object. For a battery, the potential difference is either between the two ends of the battery, or you can measure the potential difference between 2 points on *a closed circuit* - the circuit can be closed with the voltmeter if you want; if that's the case, because of the high resistance in the multimeter, you'll see 1.5 volts. Ideally the multimeter would have infinite resistance, but that's not how voltmeters work - as Evadman said, voltmeters measure current in a circuit with a very high resistance.

 

[TheLonelyPhoenix]

Originally posted by: DrPizza
wow, this has been a fun thread to read... I hope at the end of 2005, there's a category for "best e-penis fight" This is at least worthy of nomination.

Evadman, excellent post. Yes, neutral and ground are different, however, (and I think someone as well as you pointed it out) inside a house, the neutral and ground are identical - they are electrically connected at the breaker (or fuse) box for safety reasons. You could unsafely switch the ground wire and the neutral wire in every electrical outlet in the house if you wanted to, as long as the bare ground wire (which you're now using as neutral) wasn't touching anything metallic on its journey.

Also, I've seen plenty of "it has nothing to do with completing the circuit. "
Okay. Then, tell me *how* you can measure the potential difference of a battery without completing the circuit.
You can forget about answers "theoretically, I can take a voltmeter with infinite resistance and..." because that part of the theoretical is nonsense. The electrical resistance from one side of the universe to the other side of the universe is quite high, but not "infinite" So, "theoretically" , a voltmeter with infinite resistance is impossible...

Everyone seems to be expressing the same idea in two different ways. Yes, there is no potential difference between either end of the battery and the wall (or at least, not any appreciable potential difference). The potential difference in a battery is due to a chemical reaction, and the potential difference is from end to end. TuxDave's analogy was great. It's like saying how tall are you - it's in relation between your head and your feet. Not your head and some other object. For a battery, the potential difference is either between the two ends of the battery, or you can measure the potential difference between 2 points on *a closed circuit* - the circuit can be closed with the voltmeter if you want; if that's the case, because of the high resistance in the multimeter, you'll see 1.5 volts. Ideally the multimeter would have infinite resistance, but that's not how voltmeters work - as Evadman said, voltmeters measure current in a circuit with a very high resistance.

You're about 100 posts late.

 

[PurdueRy]

quote:

Originally posted by: DrPizza
wow, this has been a fun thread to read... I hope at the end of 2005, there's a category for "best e-penis fight" This is at least worthy of nomination.

Evadman, excellent post. Yes, neutral and ground are different, however, (and I think someone as well as you pointed it out) inside a house, the neutral and ground are identical - they are electrically connected at the breaker (or fuse) box for safety reasons. You could unsafely switch the ground wire and the neutral wire in every electrical outlet in the house if you wanted to, as long as the bare ground wire (which you're now using as neutral) wasn't touching anything metallic on its journey.

Also, I've seen plenty of "it has nothing to do with completing the circuit. "
Okay. Then, tell me *how* you can measure the potential difference of a battery without completing the circuit.
You can forget about answers "theoretically, I can take a voltmeter with infinite resistance and..." because that part of the theoretical is nonsense. The electrical resistance from one side of the universe to the other side of the universe is quite high, but not "infinite" So, "theoretically" , a voltmeter with infinite resistance is impossible...

Everyone seems to be expressing the same idea in two different ways. Yes, there is no potential difference between either end of the battery and the wall (or at least, not any appreciable potential difference). The potential difference in a battery is due to a chemical reaction, and the potential difference is from end to end. TuxDave's analogy was great. It's like saying how tall are you - it's in relation between your head and your feet. Not your head and some other object. For a battery, the potential difference is either between the two ends of the battery, or you can measure the potential difference between 2 points on *a closed circuit* - the circuit can be closed with the voltmeter if you want; if that's the case, because of the high resistance in the multimeter, you'll see 1.5 volts. Ideally the multimeter would have infinite resistance, but that's not how voltmeters work - as Evadman said, voltmeters measure current in a circuit with a very high resistance.



YES there is. A DMM needs flowing current as you said. This is assuming they are connected to a common ground though.

 

[TheLonelyPhoenix]

Originally posted by: rleemhui

Originally posted by: DrPizza
wow, this has been a fun thread to read... I hope at the end of 2005, there's a category for "best e-penis fight" This is at least worthy of nomination.

Evadman, excellent post. Yes, neutral and ground are different, however, (and I think someone as well as you pointed it out) inside a house, the neutral and ground are identical - they are electrically connected at the breaker (or fuse) box for safety reasons. You could unsafely switch the ground wire and the neutral wire in every electrical outlet in the house if you wanted to, as long as the bare ground wire (which you're now using as neutral) wasn't touching anything metallic on its journey.

Also, I've seen plenty of "it has nothing to do with completing the circuit. "
Okay. Then, tell me *how* you can measure the potential difference of a battery without completing the circuit.
You can forget about answers "theoretically, I can take a voltmeter with infinite resistance and..." because that part of the theoretical is nonsense. The electrical resistance from one side of the universe to the other side of the universe is quite high, but not "infinite" So, "theoretically" , a voltmeter with infinite resistance is impossible...

Everyone seems to be expressing the same idea in two different ways. Yes, there is no potential difference between either end of the battery and the wall (or at least, not any appreciable potential difference). The potential difference in a battery is due to a chemical reaction, and the potential difference is from end to end. TuxDave's analogy was great. It's like saying how tall are you - it's in relation between your head and your feet. Not your head and some other object. For a battery, the potential difference is either between the two ends of the battery, or you can measure the potential difference between 2 points on *a closed circuit* - the circuit can be closed with the voltmeter if you want; if that's the case, because of the high resistance in the multimeter, you'll see 1.5 volts. Ideally the multimeter would have infinite resistance, but that's not how voltmeters work - as Evadman said, voltmeters measure current in a circuit with a very high resistance.

YES there is. A DMM however cannot measure it. A DMM needs flowing current as you said.

Sort of. The ground acts sort of like a big pool of electrons - if you hook a wire between two unequal voltage levels, the electrons flow almost instantly (assuming no inductance to the circuit) and "even out" the voltage. A battery acts sort of like a pump, keeping a controlled voltage difference at its terminals.

 

[DrPizza]

*sigh* it's not an appreciable potential difference... almost zero.
For all our purposes, since the OP was apparently wondering why there wasn't a 1.5V potential difference, there ISN'T.

 

[PurdueRy]

made a mistake in my post, edited it for clarification. If you connect both to a "common ground" as I said, it would work. Thats all I meant

 

[TheLonelyPhoenix]

Originally posted by: rleemhui
made a mistake in my post, edited it for clarification. If you connect both to a "common ground" as I said, it would work. Thats all I meant

Okay, that's correct.

 

[grjr]

damn, I walked in on this one really late, wish I could have gotten in on this earlier- cool thread though

 

[piroroadkill]

Originally posted by: TheLonelyPhoenix
Wow. I thought the math/science threads were bad... this is WRETCHED. Half the people in this thread have completely pulled answers out of their asses.

*pulls up a lawnchair*

Keep it up, boys. I haven't had enough entertainment today.

This the correct response.

 

[sxr7171]

Originally posted by: Heisenberg
Because the voltage of the positive end of the battery is produced relative to the negative end, not the ground.

That answers the question most elegantly.

 

[amoeba]

This thread is still going on?

 

[newParadigm]

you must ground the neg end of volt meter, theres not circuit on the meter

 

[cavemanmoron]

Originally posted by: JohnCU
Let's say you have a voltmeter, and have the positive test lead touching the positive end of a battery, and the negative plugged into the neutral socket of a wall outlet. Why does it not read the voltage of the battery? Voltage is relative from point to point, and the wall should be at 0, and the battery should be 1.5 V, so it should read 1.5 V shouldn it?

April fools.........


negative goes to ground or neg,of the item your measuring,
not another "ground"

like if you cut one lug off your cord for you tv,on a 2 spade cord,
the tv will Not power up.

 

[dighn]

Originally posted by: sxr7171

Originally posted by: Heisenberg
Because the voltage of the positive end of the battery is produced relative to the negative end, not the ground.

That answers the question most elegantly.

/thread

 

[fbrdphreak]

Originally posted by: Pepsi90919
kirchoff would like to smack you now

OMFGROFL

 

[fbrdphreak]

Originally posted by: amoeba
The moral of the story is that most EEs are elitist pricks who drink too much.

You should post a solid state question next time, then the sparks will really fly.

:thumbsup: Solid state....mmmmmmmmm

 

[fbrdphreak]

Thanks guys, this was great :thumbsup:

 

[Ophir]

OP, have you figured out how batteries work yet?

 

[hytek369]

Originally posted by: KLin

Originally posted by: HappyPuppy
I'm sorry, I really don't know how to respond to your query without confusing you even more.

Translated - "You're too stupid to comprehend my explanation."

i like that

 

[DivideBYZero]

Thanks guys! This has been a really entertaining thread.

Watching you repeatedly e-cockpunch each other has had me rolling!

 

[silverbuyer]

It's now electrickery

 

[flamingelephant]

Originally posted by: JohnCU
Let's say you have a voltmeter, and have the positive test lead touching the positive end of a battery, and the negative plugged into the neutral socket of a wall outlet. Why does it not read the voltage of the battery? Voltage is relative from point to point, and the wall should be at 0, and the battery should be 1.5 V, so it should read 1.5 V shouldn it?

how 'bout this....
electricity is the flow of electrons right? so if you put the + end on a battery the electrons must flow either to or from the battery... the flow must be done in a circuit, so what leave the battery one end must return on the other, or what comes into the battery must leave on the other for there to be a circuit. No current can flow from the battery because nothing is coming back in the other end. A battery is not a source of electrons, they can't just pour out, it provides a potential difference to move the electrons, and for this to happen there has to be electrons coming and going. ]
Is that simple enough?