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Power and resistance

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CrackBadger

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I was under the impression that watts were joules expended per second but obviously thats not the case.

So Power = Voltage x Current. Lets say I have a circuit with 10V applied to it and a current of 5 amps. Thats means I have 50 watts. In this sense if I lower the resistance that will increase the current and therefore increase the power.

What about the energy being expended? Lowering the resistance will only decrease the energy being expended so its not actually putting anymore energy into the circuit?

In other words Im asking if Watts is the amount joules passing a certain point per second or is it joules being expended in a resistor per second?

When an electrical appliance says 1000 Watts on it does that mean it requires 1000 joules per second to operate or does it mean it expends 1000 joules per second. (I know in that case it probably means both but Im asking what the tag saying 1000 Watts implies)

Is this correct?
 
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CrackBadger said:
I was under the impression that watts were joules expended per second but obviously thats not the case.
THat is the case. Just other units can also work out to Watts in a not so obvious way in the same way that a lot of units work out to seconds when multipled together.

CrackBadger said:
What about the energy being expended? Lowering the resistance will only decrease the energy being expended so its not actually putting anymore energy into the circuit?
I was in this conundrum too. BUt you have to remember that since V=IR, and P=VI, then P=IxIxR =RxI^2 also . So although you are reducing the energy expended by reducing R, current increases faster than R decreases so you end up using more energy. Ahah! Makes sense now does't it?

CrackBadger said:
In other words Im asking if Watts is the amount joules passing a certain point per second or is it joules being expended in a resistor per second?
See above. Energy gets expended and can flow, and yet it never realy "passes a certain point per second". Unless you are talking about the energy in a potato or battery as you carry it around from place to place.

CrackBadger said:
When an electrical appliance says 1000 Watts on it does that mean it requires 1000 joules per second to operate or does it mean it expends 1000 joules per second. (I know in that case it probably means both but Im asking what the tag saying 1000 Watts implies)
1000W means 1000 Joules per second. The energy is required to operate and the machine operates by expending this energy as work and as waste heat and useless noise, light and whatever else. Usually they say kWh (kilowatt hours) which is a unit measure of energy and not power.
https://en.wikipedia.org/wiki/Watt-hour

Keep 'em coming. After studying for finals my house is dry and since I finished finals, I have nothing better to do than browse thsi forum.
 
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dknguyen said:
I have nothing better to do than browse this forum.
Where is your avatar of a pretty girl?
Your new avatar looks like a thug who is strangling a girl.

EDIT:
I enlarged your avatar and it shows a girl who is strangling a guy.
 
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audioguru said:
Where is your avatar of a pretty girl?
Your new avatar looks like a thug who is strangling a girl.

EDIT:
I enlarged your avatar and it shows a girl who is strangling a guy.

Holiday change. ANd it's HUGGING. not strangling.
 
Just to hijack the thread a bit futher, I was wondering what happened to the pretty young lady?
She was very easy on the eyes!
You current avatar looks hideous! Sorry!

JimB (The man with no avatar)
 
I was in this conundrum too. BUt you have to remember that since V=IR, and P=VI, then P=IxIxR =RxI^2 also . So although you are reducing the energy expended by reducing R, current increases faster than R decreases so you end up using more energy. Ahah! Makes sense now does't it?
Ah I get it. The resistance might be lowered but since the current is being raised so much there is more energy and therefore more energy being expended.

What if I had a superconductor with absolutely no resistance and I applied 2V to it. Obviously ohms law doesn't apply here but it would have an insanely high current therefore an insanely high amount of energy but without any resistance there would be no energy getting expended. Would energy be expended just because of the high resistance regardless of the resistance?

See above. Energy gets expended and can flow, and yet it never realy "passes a certain point per second". Unless you are talking about the energy in a potato or battery as you carry it around from place to place.
I read before that when theres a flow of electrons in a conductor energy travels through that conductor at the speed of light.

Keep 'em coming. After studying for finals my house is dry and since I finished finals, I have nothing better to do than browse thsi forum.
Nothing better than a symbiotic information exchange. I have heaps to learn and I learn 10 times faster when I ask questions. Glad to here these questions are helping you revise.

Holiday change. ANd it's HUGGING. not strangling.
Thats some hardcore hugging. Imagine what shes like in bed. I wish I had a girlfriend like that.
 
JimB said:
Just to hijack the thread a bit futher, I was wondering what happened to the pretty young lady?
She was very easy on the eyes!
You current avatar looks hideous! Sorry!

JimB (The man with no avatar)

She'll be back soon enough or a replacement. Don't you worry. I've been running around cleaning up my avatars lately so I know where they are because you know...it's kind of not the best thing if a girl you're with sees them for whateve reason.

CrackBadger said:
Ah I get it. The resistance might be lowered but since the current is being raised so much there is more energy and therefore more energy being expended.

What if I had a superconductor with absolutely no resistance and I applied 2V to it. Obviously ohms law doesn't apply here but it would have an insanely high current therefore an insanely high amount of energy but without any resistance there would be no energy getting expended. Would energy be expended just because of the high resistance regardless of the resistance?
You'd never use a superconducting wire as a resistor. You'd have some other load along the way which would limit the current. THe load's resistance would dominate the overall circuit resistance and determine the current flowing. If you did use a superconducting resistor with an infinite energy source then the superconductor would end up frying. In reality, your power supply would die first.[/QUOTE]

JimB said:
Thats some hardcore hugging. Imagine what shes like in bed. I wish I had a girlfriend like that.
I had to chop the caption off the picture. THe caption is "Hug an emo. They'll love you for it."
 
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dknguyen said:
Originally Posted by JimB
Thats some hardcore hugging. Imagine what shes like in bed. I wish I had a girlfriend like that.

I say, steady on there old chap!
I am a respectable middle aged businessman, I would never say such a thing, not like that cheeky young CrackBadger!:D

Besides, the experience may ruin my equipment.:mad:

JimB
 
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