simple question power, resistance, current, etc
in [Physics]
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From: Androcles on 19 Feb 2010 14:21 "Darwin123" <drosen0000(a)yahoo.com> wrote in message news:ed7229ba-64f9-4b84-970a-986ddab982ce(a)f29g2000yqa.googlegroups.com... On Feb 18, 11:23 pm, "Androcles" <Headmas...(a)Hogwarts.physics_u> wrote: > "none" <n...(a)none.com> wrote in message > Wrong. Power = voltage * current * time. <LOL> > > >So does the power of a batter change depending on the resistance of the > >circuit? Seems odd... > > Power is measured in kilowatt hours or watt hours. That's what > you pay for. <LOL> <LOL> > What one pays for is energy, not power. ============================================ How does it feel to be right for a change, drosen? On cloud 9 now, are you?
From: bert on 19 Feb 2010 15:08 On Feb 18, 11:03 pm, none <n...(a)none.com> wrote: > Is the "power" of a battery a constant? I assumed it should be, but > then I was thinking that if V=IR, say you have a battery with voltage 9 > and circuits with resistance 3 or 4.5. The current should be 3 or 2, > respectively. Then, the power would be 27, or 18, if power = voltage * > current, right? So does the power of a batter change depending on the > resistance of the circuit? Seems odd... Battery power is no constant. Please think how it works TreBert
From: Cwatters on 20 Feb 2010 13:34 "none" <none(a)none.com> wrote in message news:2010021822033416807-none(a)nonecom... > Is the "power" of a battery a constant? I assumed it should be, but then I > was thinking that if V=IR, say you have a battery with voltage 9 and > circuits with resistance 3 or 4.5. The current should be 3 or 2, > respectively. Then, the power would be 27, or 18, if power = voltage * > current, right? So does the power of a batter change depending on the > resistance of the circuit? Seems odd... No. Batteries don't have a constant power. A battery contains an amount of energy normally measured in Joules. "Power" is the rate at which that energy is extracted from the battery by the load. It's normally measured in Watts where one Watt is one Joule per Second. The power output of a car engine also depends on the load to some extent.
From: Phil H on 20 Feb 2010 14:20 On Feb 18, 9:03 pm, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "Androcles" <Headmas...(a)Hogwarts.physics_u> wrote in message > > news:znofn.59087$YO.37501(a)newsfe24.ams2... > > > > > "none" <n...(a)none.com> wrote in message > >news:2010021822033416807-none(a)nonecom... > >> Is the "power" of a battery a constant? > > > No. > > > I assumed it should be, but > >> then I was thinking that if V=IR, say you have a battery with voltage 9 > >> and circuits with resistance 3 or 4.5. The current should be 3 or 2, > >> respectively. Then, the power would be 27, or 18, if power = voltage * > >> current, right? > > > Wrong. Power = voltage * current * time. > > No, Energy = voltage * current * time. > Power = voltage * current. > > > > >>So does the power of a batter change depending on the resistance of the > >>circuit? Seems odd... > > > Power is measured in kilowatt hours or watt hours. That's what > > you pay for. > > No, power is measured in kilowatts or Watts. Energy is measured in kwH or > watt hours. That is what you pay for. > > Really, if you don't know the difference between power and energy, you are > spectacularly unqualified to answer questions about Ohms Law, and should > refrain from displaying your ignorance of basic physics in public in this > manner. It hasn't stopped him yet. Phil H
From: Phil H on 20 Feb 2010 14:25
On Feb 20, 10:34 am, "Cwatters" <colin.wattersNOS...(a)TurnersOakNOSPAM.plus.com> wrote: > "none" <n...(a)none.com> wrote in message > > news:2010021822033416807-none(a)nonecom... > > > Is the "power" of a battery a constant? I assumed it should be, but then I > > was thinking that if V=IR, say you have a battery with voltage 9 and > > circuits with resistance 3 or 4.5. The current should be 3 or 2, > > respectively. Then, the power would be 27, or 18, if power = voltage * > > current, right? So does the power of a batter change depending on the > > resistance of the circuit? Seems odd... > > No. Batteries don't have a constant power. A battery contains an amount of > energy normally measured in Joules. "Power" is the rate at which that energy > is extracted from the battery by the load. It's normally measured in Watts > where one Watt is one Joule per Second. > > The power output of a car engine also depends on the load to some extent. Another way to look at it so the resistance of the circuit comes directly into play is P = V^2/R. Power is inversely proportional to resistance. Phil H |