The concept is simple, but the terminology makes it complicated.[math]P = \frac{E}{t}.[/math]Power is a rate of energy transfer. The confusion comes from giving its units a name. Power is measured in watts. Energy is expressed in watt-hours, meaning that it can be computed by multiplying power by time:[math]E = P t[/math].A watt is defined as one joule per second. If the use of joules and seconds were more common than the use of watts and hours, then the above formulas would seem much more natural.
Time alone does not, but space-time - the entire four-dimensional reference system - contains what is called “zero point energy” or “vacuum energy”.Theoretically it should be possible to harness energy differences coming from quantum fluctuations e.g. for the propulsion of space vehicles. However, efforts to do so have so far not been successful. See e.g. Harnessing Zero-Point Energy, a Stanford coursework paper.The - so far theoretical - spacecraft propulsion device utilizing these principles is known as QVT, or Quantum Vacuum Thruster (Quantum vacuum thruster - Wikipedia). There is ongoing Research i.a. in NASA’s Advanced Propulsion Physics lab (“Eagleworks”).
Current is the actual flow of electrons past a point, it is measured in amperes, (amps). one amp is a coulomb per second. A coulomb is a specific number of electrons, and it is a huge number, If I remember right it is 6.2 x 10^18, which is equal to 62 with 17 zeros after it. As many people have already commented current is often compared to water flowing through a hose, and voltage is often compared to the pressure of the water in the hose, or the force pushing, (or forcing), the water through the hose. As you can imagine the more force you have behind the flowing water, the more water, (electrons), will go through regardless of the size of the hose. power is calculated by voltage times current in most circuits, all DC circuits, and most AC circuits, (unless the circuit has capacitors or inductors in it, which make the equation much more complicated), and not something you are probably interested in, (that would be a whole separate question in its self). power, or available power is often described as the circuits ability to do work. It is measured in watts and is lost most often in heat. Any circuit which puts off heat is losing power, unless it is intended to put off heat, like a space heater. Lights are the easiest and best known example of this. incandecent light put off a lot of heat and so are very ineficient, while LED and CFL lights put off much less heat and so use a lot less power for light output.@http://www.electrikals.com
How are energy, time, and power related?
Power is the change in work with respect to time work is a measure of energy If I have a pile of bricks that I want to move from my yard into the garage we would agree that I need energy to do this (work is force times distance so work is a measure of energy required to move 50 kg [mass with an acceleration toward the earth due to gravity] of bricks 10 meters into my garage) How time and power relate is as follows: If I want to move the 50 kg of bricks into the garage in 30 minutes, it will require a certain amount of power. If I want to do this in 5 minutes I will need even more power. Again, power is the amount of work (energy) done per unit time. The math of it is: F=ma w = F*d Power = w/t (instantaneous power is the derivative of work with respect to time)
Where is the change of energy in a power vs. time graph?
** No, the slope does NOT give energy. Energy on the y-axis and time on the x-axis, gives slope of Tan θ = Δy / Δx = ΔJoules / Δ secs As Joules = Volts * Amps * secs = watt * secs, then watts * secs / secs must = watts, and watts are units of Power, all OK. The slope gives the average power for the Δ of the graph considered. The area under the Δ part represents total energy for that time period. Now plotting power against time. Firstly consider a constant power value, result a horizontal graph. As the slope of this is Zero, it cannot represent energy = Answer. Also slope = Δpower / Δtime. This relationship equates to no other units. BUT the area under any such curve is equivalent to energy, that is power * time. It is easy to see that the average power for any duration of 1 sec, will be watts *sec = Joules. So the area and not slope yields energy. Does this help? Clarification of any point will be provided, if requested.
Why does alternating current allow efficient power transmission?
Answer is A. It sounds like you are in basic electricity, but hopefully I can explain why AC is more efficient to transmit long distances. In any circuit, the wire itself presents a slight resistance to the flow of electricity. In a very long wire (like used in cross country electrical transmission where the wire might be hundreds of miles long), this resistance adds up to a lot and becomes so high that you lose a LOT of current just in the wire itself. At the end of the wire hundreds of miles away, you have a fraction of the energy left. There are two things you can do to fix this: 1. Get a bigger, thicker wire. Bigger wire can handle more current more efficiently. It's also VERY expensive to just make all the wires bigger 2. Another option is to increase the voltage in the system. A higher voltage means less current will need to go through the wire to maintain the same amount of power at the end of the wire. Less current = less loss in the wire, which equals better efficiency. Here is where AC beats DC for long distance transmission: Long distance transmission of electricity needs to be done at VERY high voltages to reduce losses in the wire itself. You can't easily reduce a DC voltage without wasting a lot of electrical energy, but you can easily reduce an AC voltage with a transformer, and lose hardly any energy. This method with AC is very efficient. You cannot change a DC voltage with a transformer - it just doesn't work. I hope I have not confused you too much. If you need help, ask an experienced person to explain how transformers work, and ask them about what I mean by "power". If you don't already know, a high voltage at low current (amperage) can be the equivelant power of a low voltage with high current. That's what I mean by "power stays the same".
How does power, resistance and current relate?
Electrical voltage is like water pressure. A car battery may produce 12 volts (of pressure) but no power is drawn from the battery unless current (electrons) flow through a closed circuit (starter, horn, lights, etc.). P = EI (Power = Volts x Current). E = IR (Ohms Law) such that at constant (battery) voltage, to increase current resistance must be reduced. A 100W bulb produces more light and draws more power and must have a higher current and a lower resistance than a 60W bulb. If a flashlight has three battery cells, you must select the right bulb that can withstand the pressure and current of three cells (a bulb from a one-cell flashlight would instantly burn out from too much current).
Like a dictionary, pwm is just saying that an ON pulse width is controlled relative to the portion of time when the pulse is OFF: It doesn’t specify either voltage or current.In normal practice, the ”pulse ON” is a voltage with a low impedance which is like connecting to a power supply. The current from the ‘power supply’ is just a I=V/R formula. BUT the pwm means that the average current is the ratio of the pulse width ON to itself plus the between-time that it is off.Example: the pulse is on for 1/10 second and off for 9/10 second and this continues sequentially forever. The average current is 1/10 of that current which is sensed only when the pulse is ON.So the average current is controlled by the pwm ratio of ON to the period…(the ‘period’ is the name given to the addition of the ON and OFF times). In the case above, it is 10%. ==100000000010000000001000000000..SO: the voltage in a pwm signal is usually the supply voltage followed by the off-time. There is no average voltage unless you average the current produced by the circuit, like using a capacitor or inductor or momentum or a spreading function (eg..heat). People can call the average voltage of a pwm signal mathematically, but it is still ON or OFF until you do some integrating or smoothing of the signal.That said, there are other things to take into account. If the pwm signal drives an inductor, the current into the inductor increases through the pulse time. When the OFF portion of the pwm signal happens, the current wants to continue through the inductor since that is a function of the inductor. If there is no place for the current to continue, the inductor does the impossible and increases it’s voltage until that current finds a way out, usually a spark at 10s of thousands of volts. A spark plug.So much fun. I really don’t know what would happen in a perfect vacuum. Infinite Voltage Spike: New Physics: Interstellar Communications.
Power Equals Energy Divided by Time?
just like 6 = 2 * 3 is the same as 3 = 6/2 and 2 = 6/3 a = b * c are just letters standing for numbers energy comes in many forms the easiest to understand is work W = force * distance moved the force can be the weight of an object lifted or the push or pull in sliding at a steady speed against friction in electricity power is Watts = volts * amps the current energy is kilowatt hours and can be related to work or heat study the terms carefully. they say what they mean and mean what they say. but you need examples
By definition energy can be transformed into work, for instance by a motor.The power is the ratio of work with respect to the time during which the work has been delivered.Suppose we have a car having a mass of 1000 kg moving at a constant speed of 30 m/s. We want to stop this car.The kinetic energy held by the car is [math]E = {1 \over 2} m v ^2 \ = \ {1 \over 2} 1000 \ kg \ 900 \ {{m^2} \over {s^2}} \ = \ 450000 \ N m = 450 kJ [/math]If we stop this car in 10 seconds, then the average power the brakes are asked to deliver is [math]P = E / t = 450 kJ / 10s = 45 kW[/math]