What is Ac power: Definition and 47 Discussions

Instantaneous power in an electric circuit is the rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the direction of energy flow.
The portion of instantaneous power that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as instantaneous active power, and its time average is known as active power or real power. The portion of instantaneous power that results in no net transfer of energy but instead oscillates between the source and load in each cycle due to stored energy, is known as instantaneous reactive power, and its amplitude is the absolute value of reactive power.

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  1. O

    AC power loss in lossy dielectric (capacitor) with DC-bias field

    Hi there, if a dielectric (capacitor) is described with a constant permittivit eps (or C) and loss-tangent DF, how much energy ist lost when charging the capacitor by 1V? For example: C=1, DF=0.1. When charging from 0 to 1V, the lost energy (in J) is ...? When charging from 1V to 2V, the lost...
  2. oscarrod5

    Exploring Phase Potential Difference in 3-Phase Power

    I understand phase voltage (phase to neutral) well, but I'm still confused by what exactly the potential difference is between any 2 phases in 3 phase power. If you were to try to find the potential difference where 2 sine wave phases cross, then at that instantaneous point, the potential...
  3. F

    Query about the time average of an AC power supply

    Hi there, I have a query about electric power in AC systems. I am Chilean, and over here the power supply is 220 V (rms) at 50 Hz. Some countries use voltages in the range 200-230, but others use 110 V or so, at frequencies of 60 Hz. There is no uniqueness, but all work. My question is...
  4. P

    Inductor behaviour in an AC power supply

    what is actually happening when an Inductor is connected with an ac source.(i mean at the very instant of connection is made).i know emf will be induced due to change in current.(curl of E is =-time derivative of B)here my confusion is,inorder to induce emf,current should flow first,then who...
  5. J

    Making a solar powered battery with AC power socket

    It's mid summer and I think I need a project to keep busy. What better than a solar project? Problem is, I've never built a solar circuit before, let alone a battery charger. Ideally, I would like to build the equivalent of a solar powered generator. I know there's no way I'm getting as much...
  6. E

    AC power - Simulation and hand calculated values different

    Homework Statement Homework Equations P=I*(I*)*R/2 The Attempt at a Solution R1 = 12 R2 = 20 L = 0.0531H C = 265.26*10^(-6)F W = 2*pi*60 L -> jwL = 20j C = 1/(jwc) = -j10 Mesh equations: Mesh 1 (left mesh, clockwise) -Vs +I1(R1+L+C)-I2(C)=0 Mesh2 (right mesh, clockwise) I2(C+R2)-I1(C)=0...
  7. Denny Lai

    Optimizing AC Power Supply Wiring for Desired Equipment Setup

    As per the diagram, how do i change the wiring of the equipment on the outside to achieve my desired setup?
  8. YellowBelliedMarmot

    AC Power and Effective Currents

    Homework Statement I added a circuit that I drew in microsoft paint to add a visual. Sorry for its ugliness! ;D Homework Equations V = I*Z Ieff = I / sqrt(2) Qreactive = V^2 / Z Pavg = (power factor) * (Veff) * (Ieff) Sapparent = ((Ieff)*(Veff))/2 The Attempt at a Solution Since this is...
  9. anorlunda

    Insights AC Power Analysis: Part 3, Cyber Resilience - Comments

    anorlunda submitted a new PF Insights post AC Power Analysis: Part 3, Cyber Resilience Continue reading the Original PF Insights Post.
  10. toforfiltum

    Power loss in transmission lines

    Homework Statement My textbook says that high voltages are used for power transmission because according to the equation P=VI and P= I2R, power loss can be reduced. What confuses me is why the equation P=V2/R cannot used here? And if used, would be contradictory? I know that R is the...
  11. anorlunda

    Insights AC Power Analysis – Part 2, Network Analysis - Comments

    anorlunda submitted a new PF Insights post AC Power Analysis – Part 2, Network Analysis Continue reading the Original PF Insights Post.
  12. anorlunda

    Insights AC Power Analysis: Part 1, Basics - Comments

    anorlunda submitted a new PF Insights post AC Power Analysis: Part 1, Basics Continue reading the Original PF Insights Post.
  13. hdp12

    Engineering Given RLC circuit to find V over load & other complications

    Homework Statement In my Intro to EE class we have a homework assignment with the following problem: I think I finished part a but want to make sure that I am doing the problem correctly before I move on to the next part. Homework EquationsThe Attempt at a Solution
  14. hdp12

    Average and rms values of a given signal

    Homework Statement I am in an Intro to EE class and we were given a homework assignment including the following question: Find the average and rms values of the signal: x(t)=3cos(7ωt)+4 I have formulas for average power and rms but they include V & I, however the signal was given as x(t). I...
  15. B

    AC Power vs. Field Current of a DC Generator: Explained

    I am trying to understand this curve; it is AC Power vs. Field Current of a DC Generator. I am not sure what its significance is? What it's telling me? Can someone please explain it to me? See attached image. BTW... Pac = AC Power If = field current Poc = open circuit...
  16. B

    Transmission line Voltage loss

    Ok I do not know if I am right about this but : if you have an AC 120 V 60Hz generator connected to a wire of Length L(1000KM) and Resistance R going to a motor down a well, to know if you will have Voltage loss you do λ = C / F C is the speed of Light = 299 792 458 m/s F is the 60Hz λ =...
  17. J

    What Are the Best AC Power Sources for Lab Use?

    Hi. I'm joining this forum to ask about some equipment I need. At the community college where I teach, we do a lab in freshman physics where students measure the input to and output from a transformer. My AC sources are reaching the end of their lives, so I'm looking for replacements. As far...
  18. D

    Can we store ac power like dc?

    I simply wanted to know, whether we can store AC power like DC?
  19. I

    Questions on AC Power Homework: Ip = V/Z & P =(I^2)R

    Homework Statement http://photouploads.com/images/fullsizere.jpg I did not embed the image as its quite large Homework Equations N/AThe Attempt at a SolutionI'm just confused as to why Ip = V/Z (first red box)? I thought I = V/Z so why is it Ip (the peak value) in this case? As for the...
  20. Z

    Magnetic fields -- building a strong electro magnet with ac power

    Hello. I'm looking to build a strong electro magnet with ac power. I was going to use a MOT transformer so the primary was going to be the same windings. For the secondary windings though I'm trying to decide if I want to go with a higher current or voltage. I would assume that a stronger...
  21. R

    Exploring Voltage & Frequency Effects of AC Power Supply

    Explain the effects of AC power supply parameters-voltage and frequency?
  22. F

    What Is The Mathematical Relationship Between AC Power And DC Power?

    Is there a formula that shows the relationship between AC power and DC power? Something on the lines of, for example: Power of AC ... = Power of DC ... ? Thank you.
  23. A

    Does the Order of Voltage Transformation Affect AC Power Supply Output?

    Hi all, I need to create an adjustable power supply (AC) that ranges from 0-6 volts with roughly 1 ampere at 1 volt. I have a variac transformer (0-130 volts), an isolation transformer and a stepdown transformer. My question is, does it matter what order I step the voltage down? In other words...
  24. 0

    Understanding AC Power: Maximum and Minimum Currents on Resistor and Inductance

    Homework Statement I have some questions about powers in AC circuit. What is the maximum and minimum current power on resistor and inductance. Homework Equations Um = U / V2 Im = I / V2 The Attempt at a Solution prmax = U*I=(Um/V2)*(Im/V2)=(Um*Im)/2. But answer seems to actually be that...
  25. P

    Signal Generator and AC power supply

    What is a difference between sine Signal Generator and AC power supply?
  26. J

    Ac power transmission question

    Ive never understood why outlets have 3 holes. The two at the top are the voltage in and voltage out, correct? So why is there a ground if the current already has a way to return to the voltage source through the second hole? Also, i am assuming that power lines have two cables coming from a...
  27. T

    How Does AC Power Flow Through a Resistor, Inductor, and Capacitor in a Circuit?

    Homework Statement A circuit is constructed with an AC generator, a resistor, capacitor, and inductor as shown. The generator voltage varies in time ε=Vb-Va=εm cos(ωt), where εm = 122.5 V and ω = 10.35 x 106 radians/second. The resistance of the circuit is R= 132.1 Ω. The inductance is L=...
  28. L

    How are sources of AC power matched in a common grid?

    Not being an electrical engineer, I have always wondered how sources of AC power are matched when joining a common grid. I assume the power is generated at 60 hertz from each source but how is the match made so sources are in phase with one another? For instance, suppose an individual could...
  29. P

    Selecting the Right Size AC Power Supply for a Large Solenoid Experiment

    I plan on using a very large solenoid for a magnetic field experiment. I have estimated what I believe to be the inductance and resistance of the solenoid and, with the desired field to be produced, almost 20 amps will be required. After running a simple simulation, I am not sure how to...
  30. W

    Ohm's Law and AC Power: Explaining the Paradox

    I am confuse at a point that is: I equation P=IV there is an inverse relation between I and V But according to ohm law there is direct relation between I and V. How in in ac Power transmission line 1100 volt cause small current than 220 volt... please solve my this trouble... Everyone...
  31. D

    AC Power RC series circuit low pass filter, find frequency given gain.

    1. You have a series circuit consisting of a ac power supply, a 600 ohm resistor and a 73 nF capacitor. If the circuit is configured as a low pass filter, what frequency will cause the gain to be 0.25? 2. If the circuit is configured as a high pass filter, what frequency will cause the gain...
  32. P

    AC Power Meter & Remote Switch

    Hi, I have forgo my previous idea of Tesla coil as my final year project and now moved on in doing an AC power meter monitoring, which monitors the kWh, voltage, current consumption of a device and remotely controlled switch to turn off/on the device.This power meter should be implemented like a...
  33. T

    How Does Current Return to the Source Through the Ground in AC Power Lines?

    So i know the whole picture starting from power from the generating plants that go all the way to our homes..and the ground serves as a return path to complete the circuit..What i don't get is...how does that current find its way back to the source through ground?..is the source somehow...
  34. D

    Understanding the Split Phase: How Does AC Power Work in the US?

    Regarding this topic, https://www.physicsforums.com/showthread.php?t=421945" a question sprung into my mind. How many conducting cables go to my home circuit to deliver the power from the grid? If heard these electrician's jargon words: 1) phase (up to 3) 2) null 3) ground...
  35. H

    Changing Frequency of AC Power Supply: Circuitry vs Generation

    Can anyone tell me what the most standard way of changing the frequency of an AC power supply is? Can it be done with circuitry or does the method of generation need to be set at the desired frequency?
  36. James889

    Then you can solve for the two currents.

    Hai, I have the following circuit: http://img152.imageshack.us/img152/1848/powertransfer.png My task is to calculate the power dissipated in the resistor, and also the power delivered by the V1 source. Here's what i tried. First i /dev/null'ed the second source and calculated the...
  37. W

    What to do with a DC to AC power inverter?

    I recently acquired by accident a 750 watt DC to AC power inverter, designed for powering AC appliances off of a car battery or other 12V power source. I have no need for such functionality. I am really interested in high voltage projects and I was wondering if there are any interesting...
  38. W

    What to do with a DC to AC power inverter?

    I recently acquired by accident a 750 watt DC to AC power inverter, designed for powering AC appliances off of a car battery or other 12V power source. I have no need for such functionality. I am really interested in high voltage projects and I was wondering if there are any interesting...
  39. R

    Electronic control of ac power

    Hi Experts, I would like to make an electronic circuit to control AC power to switch on and off a light bulb based on sensor. Being new to this , i hope know what aspects i need to pay attention to when using DC to control AC? sincerely Ramone
  40. D

    AC Power Calculations: Understanding Real & Reactive Powers

    Hi, I am a bit lost with AC circuits on the whole and could use some dumbed down explanation on the matter. Taking an example from course material: (Components connected in parallel. "Ladder connection") ------ l l l l l J C L R l l l l l ------ Where J = 1 (30 degrees)...
  41. E

    AC Power and Combining Volt/Current

    Homework Statement One of the reasons we use AC power instead of DC is that with AC, we can use a single wire with a maximum voltage of 220V to return 660V. This is done by combining 3 lines of 220V into a single one. How can this be done without exceeding the wire's max voltage of 220V? My...
  42. O

    AC Circuits II: AC Power Generator

    Homework Statement A An AC generator supplies an rms voltage of 110 V at 60.0 Hz. It is connected in series with a 0.300 H inductor, a 5.80 μF capacitor and a 236 Ω resistor. What is the impedance of the circuit? B What is the rms current through the resistor? C What is the average power...
  43. E

    Two AC power sources - connection?

    two AC power sources -- connection? i am working on a control system for a compressed air energy storage system for a wind turbine (generates ac). the goal is to shave peak power consumption, so at night the compressor will charge (either by the wind or by the grid), and during peak hours, it...
  44. S

    What Happens if You Power a DC Device with AC Voltage?

    I was just curious what would happen if a device working at for example, 5 V DC voltage, is given 10 V peak to peak AC voltage. Would the device still operate? maybe it depends on the device but can someone briefly explain ..? thanks!
  45. I

    Connecting AC Power Lines: Understanding Wattage & Current

    What is the proper way to connect several ac power lines into one line. So let's say if you had 20 lines and each had a 10 volts and 1 amp of power so 10 watts AC. When connecting them into one line would you have 200 watts. Also with it being alternating what would happen when the current is in...
  46. P

    How Do You Calculate Electrical Parameters of a Heater in an RLC Circuit?

    Homework Statement The figure below shows the time variation of the current through an electrical heater when it is plugged into a 240 V, 50 Hz outlet. 1) What is the peak voltage? 2) What is the rms value of the current drawn by the heater? 3) What is the resistance of the heater...
  47. I

    Designing 12V DC-220V AC Power Inverters

    How to design 12vdc-220vac 2000,3000,5000 and 10000watts. I need a circuit diagrams and detailed discriptions.Thanks Ismail Dari.