# What is Electrical power: Definition and 55 Discussions

Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second.
Electric power is usually produced by electric generators, but can also be supplied by sources such as electric batteries. It is usually supplied to businesses and homes (as domestic mains electricity) by the electric power industry through an electric power grid.
Electric power can be delivered over long distances by transmission lines and used for applications such as motion, light or heat with high efficiency.

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1. ### Question about electrical power compared to mechanical power

I am new here and I am seeking for help:) Thank you so much. In engineering, electrical formula often analogy to mechanical formula. eg. power[W] = pressure x volume flow rate vs power[W] = voltage x current My question is could we make the simplest unit between electrical and mechanical...
2. ### How to calculate the electrical power output using the Organic Rankine Cycle?

Basically this would be a closed loop geothermal system for electrical power generation. The system would consist of 2 Horizontal Wells connected creating a U-shaped closed loop cycle using thermosiphon effect, with constant recirculation. It's not really a conventional geothermal power...
3. ### What is the electrical power output of a turbofan engine?

Hello All, Happy New Year! A typical modern turbofan engine system creates lift as well as propulsion for the aircraft. Somewhere inside the system, the fast rotating device also works as a generator (alternator) to produce the electricity powering electrical/electronics equipments. What is the...
4. ### Physics Equations for Electrical Power

I'm in year 11, doing Physics for GCSE and my actual ending GCSE is on Friday which Is where I finish school. I'm 16 and in the UK, I need help with the following equations: P = I^2 x R (why is this equation used) - all the power equations - How to calculate uncertainty << Mentor Note -- OP...
5. ### Other Undergraduate research or thesis topics in electrical power

Hi I am an electrical engineering student, would like to do research and or a thesis in electrical power engineering. However, because our university does not offer any courses on this topic, I am left alone to peruse the books and literature and find some topic of interest. do not know if this...
6. ### Determine electrical power generated by changing B-field through a loop

Homework Statement A circular loop of radius a and resistance R is placed in a changing magnetic field so that the field is perpendicular to the plane of the loop. The magnetic field varies with time as B(t) = B_0 * e^(-t) where B_0 is a constant. Determine the electrical power in the circuit...
7. ### Electrical Power Loss Equations Confusion

Why is the equation Power Loss = I^2*R rather than Power Loss = V*I? What I mean is why use I/R to represent V? Also if Power Loss is equivalent to V*R, doesn't step up transformers which creating higher voltage also cause Power Loss to increase which contradicts to textbooks stating that power...
8. ### Work done by voltage source

Is the work done by a constant voltage source positive or negative when current is opposite to emf?
9. ### Calculate Efficiency of Motor Lifting 0.050kg Block at 0.40m/s

Homework Statement A motor lifts a block of mass 0.050kg at a constant velocity of 0.40m s-1. The current in the motor ia 85mA and the potential difference across it is 3.0V. Calculate the efficiency of the motor Homework Equations Ek = 1/2 x mv2 Electrical power = VIt The Attempt at a...
10. ### Electrical power corridor supply

What is required to bring hydro lines on towers together?
11. ### Electrical power of a lightbulb

Homework Statement Two identical light bulbs are connected to the ends of the battery. In the first case they are connected in series and in the second they are connected in parallel mode. What is the ratio of the electrical power of light bulbs connected as mentioned? Homework Equations...
12. ### Electrical power system of a spacecraft mission to a comet

Homework Statement Calculate the solar array power capacity required at the start of the mission Mission duration is 10 years Distance from the Sun at end of mission is 4.8x[10][/8] km The power requirement for the spacecraft at the end of life is 510 W Solar array degradation over mission...
13. ### Electrical power generated by wind turbine

Homework Statement Homework Equations P=FV The Attempt at a Solution To calculate the mass of wind swept by turbine in a second, I take 2000m2 ×10ms-1×1.3kgm-3.Then, to calculate the force I multiply the answer with 10ms-1. Since they want the power and the yield is 50%. I multiply the...
14. ### How does a car's loads affect it's fuel consumption?

Hi, so I was wondering about how the car's LED, MP3/IPOD, AC systems consumes up electrical power and then to fuel? Let's say that the loads are running for 5-7 hours. Thanks for the replies/ideas!
15. ### International Standard of Electrical Power Cable

Hello there, All Electrical Engineer fellas, :smile: Someday ago, I had been assigned to conduct a building audit of one company in Indonesia. For completing this task, I need all international standard about electrical equipment installation, especially for wiring / cable. Is there anyone...
16. ### Electrical Power Engineering Studying

Hello everyone from PhysicsForums, At the moment, I'm nearly 90% of my first year completion in Finnish University of Applied Science. During my first year, I have acquired some basic knowledges about circuit analysis, Labview and MATLAB programming, basic mathematics and physics. For the next...
17. ### Electrical power with kW and kWh - Pwr avail?

Homework Statement Req'd to calculate power avail for propulsion. Given 2x 475kW fuel cells, 6400 kWh lead-acid battery. Ships machinery power requirement is 1100 kW at any given time, and battery max discharge rate is 1.2 kW/kWh. Homework Equations I'm not sure I fully understand the how...
18. ### Electrical Power Equation Contradiction

We know that the rate at which electrical work is done (electrical power) is defined as: P = I2*R , or: P = V2/R The formula P = V2/R implies that if the resistance of an electrical component (R) (for example, a light bulb) is decreased, the power consumption (P) will increase hence the...
19. ### Electrical power out of R134a phase changes

Hi My 2'nd year of engineering doesn't quite let me to find an answer to the following problem: In a nutshell: I want to use rankine cycle to extract 5kW worth of electrical energy from a system utilizing R134a as working fluid. The properies of R134a are as follows: Tag R134a...
20. ### What's the electrical power (physically)

I have a question to depth understanding electricity what's the thing that make electrical power appear? I mean that when generating electrical power We generate emf (voltage) and if the circuit was closed we get current ! HOW THEN ELECTRICAL POWER APPEARD AS AN IMPORTANT PARAMETER
21. ### Physical Science Question on Electrical Power and Energy

1. An electric space heater draws 15.0 A from a 120 V source. It is operated, on average, for 5.0h (hours) each day. a) How much power does the heater use and b) At \$.10 per kWh, what does it cost to operate the heater for 30 days? 2. Suppose each person in the United States uses 12,000 kWh of...
22. ### Equation relating rotational velocity and output electrical power

What is the equation that relates the angular velocity of an alternator rotor with its output electrical power, voltage and frequency (not necessarily just one equation) . And for a DC generator? I know that when you calculate the power generated by a turbine you multiply its efficiency of...
23. ### Why Is Electrical Power Conducted at High Voltages?

Hey guys why is power conducted at very high voltages? doesn't that increase the current and thus the heat generated because p=v.i?
24. ### Electrical Power - Equation Questions:

A 1.5V rechargeable cell is labelled 2300 mA h. This means that it can supply the equivalent of 2300 mA for one hour. b) How much energy does the cell store in: i- mWh? ii- J? and c) How long can four cells, connected in series, light the bulb? for b) i- I got: W = V x Q, so W = V x I...
25. ### Imperial Valley electrical power out.

My sister lives in San Diego and posted on FB that much of the SW US is out of power. Have been snooping around for news for the last 10 minutes and ran across the following: During a level 9 earthquake, it kind of makes sense to shut down the reactors, but during a power outage? But...
26. ### Thoughts on Stirling engines as source of electrical power in space

Curious your thoughts about the use of a Stirling engine to power a space station, auxiliary power for space ships inside the inner solar system, and power for space colonies in the inner solar system. I think a Stirling engine would be great to generate an electrical field, and thus provide...
27. ### Dipole antenna and electrical power

Homework Statement It's me again:) I have an antenna which emit the electrica power with the formula P given at the relevant equations. Now I shall calculate the impendance which the current generator "recognizes" which feeds the antenna with the current. Homework Equations...
28. ### Electrical power systems question

Homework Statement 3. Generator G in the above system is a steam turbine driven, 4-pole round rotor synchronous generator and has the following data: Rated output 250 MVA Rated Voltage 13.8 kV Rated frequency 60 Hz Rated power factor 0.85 lag Maximum reactive power 140 MVAr...
29. ### What is the relationship between electrical power and torque in a generator?

Lets say we have a fixed voltage output on a generator... As we load it down (require more current to flow out of it), the generator needs to apply more torque to supply the power. Why? What is resisting the rotor from turning?
30. ### Correct term: thermal power & electrical power

Dear all, This question might sound trivial but for weeks I am unsure about the correct answer: 1. Given there is a radiator. The radiator's performance is stated in [Watt]. 2. Given there is a nuclear plant. The plant's performance is also stated in [Watt]. Is it correct English to...
31. ### How Much Electrical Power Does a 75% Efficient Pedal-Operated Generator Produce?

Hi: Would somebody please check to see if I am on the right track with this problem. Many thanks Homework Statement An 80kg man on a step-exercise machine climbs a staircase 3.0m high in 8.5s. If he works at the same rate to drive a pedal-operated generator with an efficiency of 75%, how...
32. ### Problem in solving a sum in generation part of electrical power system

hi, I am just not able to solve this problem in the generation part of electrical power system. I am not able to plot the load curve and the load duration curve.sum is as follows:- A power station has to meet the foll demand:- GROUP A: 200 kw between 8 am and 6 pm. GROUP B: 100 kw between...
33. ### Electrical power generation and distribution in an aircraft

i would be delightful if someone Can suggest me any book for this topic-'Electrical power generation and distribution in an aircraft. i am doing my thesis work on it. i would like to add few more points with your help. Thank you
34. ### GaAs temperature calculation induced by electrical power

hello I have a question. If 10V and 100mA is injected to GaAs laser ridge size is 1mm(length), 10um(width), 5um(thickness), which temperature can be generated in the ridge? the ridge is covered by gold for the electrical contact. Is it possible to calculate? I tryed to serch the...
35. ### Introductions to Electrical Power Systems

Hello everyone, Could anyone recommend any good introductions to Electrical Power Systems and Power Engineering? I would be very interested to find out more about the history of why we choose the frequencies we use for power systems. For instance, why is it so important that frequency be...
36. ### Efficiency of electrical power plant

Homework Statement An electrical power plant manages to transfer 88 percent of the heat produced in the burning of fossil fuel to convert water to steam. Of the heat carried by the steam, 40 percent is converted to the mechanical energy of the spinning turbine. Which best describes the...
37. ### Deciding on a Master's in Electrical Power Engineering: Which Field to Choose?

I'm going to take master degree in electrical power engineer at german but it's hard to descide which field is more required in market and has good future so would you help me: 1- Control 2-High voltage 3-Transmission & ditribution 4- renewable energy 5- Other (please verify) thanks for help
38. ### What is the formula for electrical power in a DC circuit?

I am studying DC circuits and trying to derive formula for power; that is in fact P = I.Vab where Vab is the potential difference between two terminals of a circuit element. From my previous studies, I know that. P = dW / dt I assume that for a small interval, dt, a single...
39. ### Electrical Power to Mechanical Power

Hello! We (myself and the other folks at my company) have a couple of questions about the proper way to compare electrical energy to mechanical energy. Our application involves holding a load at zero speed, as well as moving it back and forth at varying speeds. Most of the time, our motor...
40. ### Electrical Power - Cost of kW*hr

Homework Statement An electric air conditioning unit draws 15 amps of direct current from a 134 V direct voltage source, and is used 24 hours a day during 21.1 days in July. How much will the electricity cost for the month if the local electrical rate is 9.9 /kW· hr? Answer in units of...
41. ### Electric Power: P=VI Explained

I know that P = VI where P is power in watts (joule/second), V is voltage in volts (joule/coulomb), I is electric current in amps (coulomb/second). My idea of work is like this. I use force (in Newton) to pick up a stone and take it from point A to point B with a distance d in meters. I...
42. ### Electrical power from turbine?

Homework Statement A small dam produces electrical power. The water falls a distance of 27m to turn a turbine. If the efficiency to produce electrical energy is 65%, at what rate must water flow over the dam to produce 780 kW of electrical energy? Homework Equations v2 = u2 + 2as...
43. ### Confusion regarding electrical power

From P=(V^2)/R, it suggests that as you increase the resistance, you decrease the electrical power. Conversely, from P= (I^2)R, it suggests taht if you increase the resistance, you increase the electrical power. Please can someone explain the above. Thanks alot
44. ### What is the power of the engine in a moving elevator?

Homework Statement 1.Lets look at the motion of a lift in two situations:a) The lift moves upward with a constant speed of 2m/s.how much electrical power goes the engine of the llift use if the efficiency of the engine is 90% ? b) Whats the power at time 1.5s when the lift started upwards...
45. ### Wireless electrical power tranmission.

For those of you that don't read yahoo news, there was an article this morning about Intel developing wireless power transmission. http://news.yahoo.com/s/afp/20080821/ts_afp/usitinternetenergychipcompanyintel" Apparently there was a demonstration where they lit up a 60watt light bulb across...
46. ### Lightning Strike and electrical power surge

Recently, lightning hit near my home (as best as I could tell, not my home directly) and caused considerable damage to my home computer. I have a wireless network with 2 desktops...one direct wired using ethernet cable and the other using a NIC card. When the lightning struck, my wired...
47. ### Real power not the only useful form of electrical power?

"Real power" not the only useful form of electrical power? Reactive power has been associated with "imaginary current" and "magnetizing power". From my understanding, this power would tend to move at right angles to the flow electrical charges. In a system that is powered by a battery...
48. ### How much power is needed to hold a 500g object stationary against gravity?

Hi, I am trying to calculate the electrical power (watts) needed to hold a 500g object stationary against gravity. It’s been a while since my physics days and each time I do the calculations I come up with a different answer. Any help would be much appreciated. Thank you. Sam
49. ### Solve Electrical Power Homework: 5.3kW

Homework Statement A power station delivers 520 kW of power to a factory through wires of total resistance of 3ohms. How much less power is wasted if the electricity is delivered at 50000V instead of 12000V? Homework Equations V=IR P=IV=I^{2}R=\frac{V^{2}}{R} The Attempt at a...
50. ### Can the Work Done by an Inductor Exceed the Electrical Power Used to Make It?

Energy stored in an inductor is equal to: \frac{1}{2}L\mathbf{I}^2 Where L is the inductance in henries and I is the current in amps. The energy stored in the inductor doesn't depend on how fast the current is attained, just the fact that it has some inductance and some current. However, how...