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cowboyro
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join:2000-10-11
CT

2 edits

cowboyro to Davesnothere

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to Davesnothere

Re: [Electrical] How many watts are in an amp?

said by Davesnothere:

P = E x I (Power in Watts = EMF in Volts x Current in Amperes)

That is only true in DC or for pure resistive loads.
If you connect a capacitor or a quality inductor to an AC source you will have a current, yet the power will be 0.
Ex a 100uF capacitor will draw 4.5A @120V
Yet the power is 0W. [edit: watts]

DarkLogix
Texan and Proud
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join:2008-10-23
Baytown, TX

DarkLogix to cowboyro

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to cowboyro
You need to go back to physics class.

There's lots off little things like that.

If the box is moving at a constant speed then the Net force is 0 but the person moving it is applying a force and by definition if it has a force it has an acceleration its just it happens to be countered.

When you look at it purely mathematically you can often find things that are odd.

and yes x/t/t is the same as x/t^2 its basic algebra.
And while when displacement is a straight line speed can be used instead of velocity because they'll be equal as the difference is speed=distance/time and velocity is v=displacement/time

in the application of solving for the acceleration component of a force without regard to actual acceleration taking place (IE if an object were falling gravity is still acting on it even if it's reached terminal velocity) then if you know the force and the mass you can solve for the acceleration even if its not really accelerating.

Davesnothere
Change is NOT Necessarily Progress
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join:2009-06-15
Canada

Davesnothere to cowboyro

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to cowboyro
said by cowboyro:

said by Davesnothere:

P = E x I (Power in Watts = EMF in Volts x Current in Amperes)

That is only true in DC, or for pure resistive loads.

I believe that I said this.
said by cowboyro:

If you connect a capacitor or a quality inductor to an AC source you will have a current, yet the power will be 0.

Ex a 100uF capacitor will draw 4.5A @120V, yet the power is 0.

Wait until you get your electric bill for doing tests like that, if you do them for any significant period of time !

I didn't want to take things even further OT, but here goes....

The power drawn by a reactive load is NOT zero.

It is only that consumer grade measurement devices cannot properly measure and display it.

Power WILL be drawn when you put that capacitor across the 120 Volt line.

Try touching the capacitor after it has been drawing 'no power' for a while.

Oh, and best get the first aid kit out before hand.

cowboyro
Premium Member
join:2000-10-11
CT

cowboyro to DarkLogix

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to DarkLogix
said by DarkLogix:

and by definition if it has a force it has an acceleration its just it happens to be countered.




NET FORCE acting upon the object, not individual forces.
»www.physicsclassroom.com ··· leration
said by DarkLogix:

if you know the force and the mass you can solve for the acceleration even if its not really accelerating.

You can solve with the eyes closed. ZERO.

Anonymous_
Anonymous
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join:2004-06-21
127.0.0.1

Anonymous_ to cowboyro

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to cowboyro
said by cowboyro:

said by SuperNet:

How many watts are in an amp?

How many seconds are in a yard?
Different, independent units of measurement.

incorrect it can be calculated we just need to know how fast you are going then we can know how many seconds in a yard

i.e
a car is going 60 miles per hour and will travel 60 miles in 1 hour

cowboyro
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join:2000-10-11
CT

cowboyro to Davesnothere

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to Davesnothere
said by Davesnothere:

Wait until you get your electric bill for doing tests like that, if you do them for any significant period of time !

Poor choice of words -my bad. 0 Watts, not no power.
Residential meters do not measure and bill reactive power, just active.
said by Davesnothere:

It is only that consumer grade measurement devices cannot properly measure and display it.

Yes they can - as long as they measure the power factor. Just measuring voltage and current alone is not enough to calculate the energy used.

nunya
LXI 483
MVM
join:2000-12-23
O Fallon, MO

nunya to SuperNet

MVM

to SuperNet
If I get what the OP is digging for:
You do not want to exceed 1440 watts on a 15A 120V circuit or 1920 watts on a 20A 120V circuit.

cowboyro
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join:2000-10-11
CT

cowboyro to Anonymous_

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to Anonymous_
said by Anonymous_:

incorrect it can be calculated we just need to know how fast you are going then we can know how many seconds in a yard

Who said I am going at all?

Anonymous_
Anonymous
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join:2004-06-21
127.0.0.1

Anonymous_

Premium Member

use GPS as your tac meter

pende_tim
Premium Member
join:2004-01-04
Selbyville, DE

pende_tim to Davesnothere

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to Davesnothere
said by Davesnothere:

I believe that I said this.

So did I in the second or third post. LOL....

For a PURE reactive or capacitive load the Power Factor is 0.0 which makes the watts 0.0. This is because any energy transferred to the device is returned to the power source when the electrical polarity starts to reverse. So you are "borrowing" from the power source when charging and returning when discharging.

Since there is no device that has a PURE reactive/capacitive nature the power factor will never be 0.0. Any resistance will cause losses and thus all the energy will not be returned to the source. Even a high quality capacitor has leads/plates that have resistance.

As to why you get a shock from a capacitor? It depends when you disconnect it. If it is removed from the circuit before it has a chance to "return" it's "borrowed" energy you will be "billed" for that energy, and you will have the borrowed energy returned to you in the form of a shock.

Jack in VA
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join:2014-07-07
North, VA

Jack in VA to SuperNet

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to SuperNet
said by SuperNet:

How many watts are in an amp?

You have to know any two of these 3 variables.
Volts, ohms, amps

use the calculator at the link below

»www.rapidtables.com/calc ··· ator.htm

Thane_Bitter
Inquire within
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join:2005-01-20

Thane_Bitter to SuperNet

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to SuperNet
said by SuperNet:

I have 6 T8 Bulbs for lights

6x32w
said by SuperNet:

52in Sony LCD TV

~200 w (less if its an led model)
said by SuperNet:

Bathroom fan

50w
said by SuperNet:

very old stereo(1999)

1999 isn't old! say 10w on standby
said by SuperNet:

Wii, and a Bluray player.

20w
Edit: There is an additional load in the ballasts for the tube lights, it depends on the type of ballast. The information is just ballpark, get a energy meter for actual results.

Davesnothere
Change is NOT Necessarily Progress
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join:2009-06-15
Canada

Davesnothere to cowboyro

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to cowboyro
said by cowboyro:

said by Davesnothere:

It is only that consumer grade measurement devices cannot properly measure and display it.

 
Yes they can - as long as they measure the power factor.

Just measuring voltage and current alone is not enough to calculate the energy used.

 
I agree that they would need to measure the power factor, and said so in different words.

But I was also expressing sincere doubt in my earlier post(s) that consumer grade energy meters (the kind which plug inline between a load and a wall outlet) have been designed to do that, given their low price point.

Jack in VA
Premium Member
join:2014-07-07
North, VA

Jack in VA

Premium Member

Unless it's a very large induction motor the Power Factor can be assumed to be close to one.

SparkChaser
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join:2000-06-06
Downingtown, PA

SparkChaser to Davesnothere

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to Davesnothere
said by Davesnothere:

But I was also expressing sincere doubt in my earlier post(s) that consumer grade energy meters (the kind which plug inline between a load and a wall outlet) have been designed to do that, given their low price point.

The Killawatt does but I can't attest to the accuracy. I guess I could test it.

pende_tim
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join:2004-01-04
Selbyville, DE

pende_tim to Jack in VA

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to Jack in VA
said by Jack in VA:

Unless it's a very large induction motor the Power Factor can be assumed to be close to one

If it is really large and a synchronous machine, it can be overexcited and used to correct powerfactor.

But we digress from the OPs question ....
kherr
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join:2000-09-04
Collinsville, IL

kherr to SuperNet

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12,268,458,893.23517/0 .......
TheMG
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join:2007-09-04
Canada
MikroTik RB450G
Cisco DPC3008
Cisco SPA112

TheMG to Davesnothere

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to Davesnothere
said by Davesnothere:

But I was also expressing sincere doubt in my earlier post(s) that consumer grade energy meters (the kind which plug inline between a load and a wall outlet) have been designed to do that, given their low price point.

A power meter that doesn't account for power factor would be quite useless.

Yes, pretty much all of these plug-in power meters do account for power factor. Fairly trivial to accomplish these days with the prevalence of inexpensive microcontrollers.

Some of them are not very accurate but there are some such as the kill-a-watt that are actually quite reasonable.

garys_2k
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join:2004-05-07
Farmington, MI

garys_2k to Davesnothere

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to Davesnothere
said by Davesnothere:

But I was also expressing sincere doubt in my earlier post(s) that consumer grade energy meters (the kind which plug inline between a load and a wall outlet) have been designed to do that, given their low price point.

Actually, the Killawatt provides volts, amps, watts, VA and power factor.

For the OP, what causes the breakers to trip and wires to get hot are amps. Watts, as has been discussed, are most likely approximately equal to volts X amps so amps can be figured by watts / 120. But a Killawatt tells you the whole score.

NS4683
join:2000-08-25
NJ

NS4683 to Anonymous_

Member

to Anonymous_
said by Anonymous_:

use GPS as your tac meter

Lol, what? How can a GPS do that?

Jack in VA
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join:2014-07-07
North, VA

Jack in VA to pende_tim

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to pende_tim
said by pende_tim:

said by Jack in VA:

Unless it's a very large induction motor the Power Factor can be assumed to be close to one

If it is really large and a synchronous machine, it can be overexcited and used to correct powerfactor.

But we digress from the OPs question ....

No experience with a synchronous machine for PF correction. Most of the newer installations used 15kv capacitor banks and the last place had co-generation so it was a moot point.

Anonymous_
Anonymous
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join:2004-06-21
127.0.0.1

Anonymous_ to NS4683

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to NS4683
it can tell you your speed

NS4683
join:2000-08-25
NJ

NS4683

Member

What do you mean by "tac" meter? Did you mean tachometer?
MaynardKrebs
We did it. We heaved Steve. Yipee.
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join:2009-06-17

MaynardKrebs to SuperNet

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Yeah, but how do I express watts in leap furlongs per long hundredweight?

Raphion
join:2000-10-14
Samsara

Raphion to Davesnothere

Member

to Davesnothere
said by Davesnothere:

This is what shows up on the energy meter at your power panel.

I am 99.9% sure that residential power meters count only Real power, not Reactive power (volt-amps).

Actually I take that back, the digital "smart meters" track both, but billing is based only on the real power. The old dial meters only count real power though.

Jack in VA
Premium Member
join:2014-07-07
North, VA

Jack in VA

Premium Member

said by Raphion:

said by Davesnothere:

This is what shows up on the energy meter at your power panel.

I am 99.9% sure that residential power meters count only Real power, not Reactive power (volt-amps).

Actually I take that back, the digital "smart meters" track both, but billing is based only on the real power. The old dial meters only count real power though.

Residential meters don't need to measure Reactive Power as there is not much in a home to effect the PF.

PSWired
join:2006-03-26
Annapolis, MD

PSWired to cowboyro

Member

to cowboyro
said by cowboyro:

said by tomupnorth:

Pie. Power (Watts) equals Current(Amps) times Energy (volts)

You already forgot. Energy is expressed in Joules and/or derived units (such as watt-hour)

He got the energy annotation wrong, but the E in P=IE stands for electromotive force. Back in the early EE days this was used in lieu of v for voltage.

Davesnothere
Change is NOT Necessarily Progress
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join:2009-06-15
Canada

Davesnothere to MaynardKrebs

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to MaynardKrebs
said by MaynardKrebs:

Yeah, but how do I express watts in leap furlongs per long hundredweight?

 
Don't laugh.

A single horsepower = approximately 746 watts, IIRC.
Davesnothere

Davesnothere to Jack in VA

Premium Member

to Jack in VA
said by Jack in VA:

said by Raphion:

said by Davesnothere:

This is what shows up on the energy meter at your power panel.

I am 99.9% sure that residential power meters count only Real power, not Reactive power (volt-amps).

Actually I take that back, the digital "smart meters" track both, but billing is based only on the real power. The old dial meters only count real power though.

Residential meters don't need to measure Reactive Power as there is not much in a home to effect the PF.

 
I'm not sure whether they track both types of energy (power), but you are generally correct that most homes use mainly resistive loads.

Most of the larger load residential devices are resistive, especially those which are meant to create heat as their primary function or job. - These include :

Electric heating,
Water heater,
Clothes dryer,
Stove,
Most plugin kitchen appliances - maybe not the Microwave,
Not sure about air conditioning.

OTOH, Computer Gear and Consumer Electronics are smaller loads, but my own experience suggests that they may be somewhat reactive, based upon how their power supplies function, and readings I have taken. - How much that may matter would depend upon how much of that stuff that you have.
MaynardKrebs
We did it. We heaved Steve. Yipee.
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join:2009-06-17

MaynardKrebs to Davesnothere

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to Davesnothere
said by Davesnothere:

said by MaynardKrebs:

Yeah, but how do I express watts in leap furlongs per long hundredweight?

 
Don't laugh.

A single horsepower = approximately 746 watts, IIRC.

Funnily enough, I knew that.