I will argue that power is consumed (and wasted). Conservation of power can be viewed as accounting. Yes, you can account for it all, but a light bulb draws power to make light and heat. In most cases, the heat is considered waste heat, and a better (type of) bulb can produce the same light with less heat.
I will further argue that speed consumes gasoline. The amount of gasoline to go a given distance varies with speed. At higher speeds it grows as approximately v³, while the time to cover the distance decreases as 1/v. Of course, at very low speed, near zero, the engine wastes gasoline idling. There is a sweet spot, some optimum speed, somewhere in between, with increased gasoline consumption (for the trip) at higher or lower speeds. The regimented "only these words may be used" approach may not fully analyze the situation. For electrical energy usage, it makes a lot of sense to look at instantaneous power (which is consumed and only partially transformed into anything with utility), running time, and duty cycle (when there are multiple power states). Failure to consider all of these is likely to lead to misunderstanding. A prime example is what does it cost to bake a loaf of bread for an hour in a 2 kW oven at $0.20/kWh, an example from a prior note. The correct answer is NOT $0.40, it is "I don't know. Ovens have thermostats and the element switches on and off. I don't know the duty cycle." My observation is that once the oven reaches setpoint, the duty cycle is moderately low at bread baking temperatures. I would guess the cost is nearer $ 0.05 or $0.10, but it is a guess with no data on the particular oven involved. Power and energy are different, but I resist the notion that they are "quite different" as they are so related. Formally, if either is known as detailed function of time, the other can be determined as power is the derivative of energy with respect to time, or energy is the integral of power over time. For an electrical device with only one power state, perhaps it doesn't "consume" power but it "draws" or "requires" constant power, and the energy it consumes is that power multiplied by time. Reality is generally multiple power states and a more complex sum or integral. ________________________________ From: "[email protected]" <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Thu, January 13, 2011 10:36:20 AM Subject: [USMA:49492] Re: Screen size conundrum John (Steele) is usually very comprehensive and precise. I'm surprised that John got it wrong by arguing that rates can by "consumed." Power is a *rate* (J/s). A rate can never be "consumed." An appliance can have a "power rating." The "rating" is never "consumed." An appliance can have a "power requirement." The "power requirement" in never consumed. Similarly, "speed" is a rate. Speed is never "consumed." Gene, in support of Pat on this distinction. ---- Original message ---- >Date: Thu, 13 Jan 2011 03:52:32 -0800 (PST) >From: "John M. Steele" <[email protected]> >Subject: [USMA:49491] Re: Screen size conundrum >To: "U.S. Metric Association" <[email protected]> >Cc: USMA Metric Association <[email protected]> >... > Each electrical appliance has a > certaion power consumption. ...
