# What is Electric energy: Definition and 54 Discussions

Electrical energy is energy derived as a result of movement of electrons. When used loosely, electrical energy refers to energy that has been converted from electric potential energy. This energy is supplied by the combination of electric current and electric potential that is delivered by an electrical circuit (e.g., provided by an electric power utility). At the point that this electric potential energy has been converted to another type of energy, it ceases to be electric potential energy.
Thus, all electrical energy is potential energy before it is delivered to the end-use. Once converted from potential energy, electrical energy can always be called another type of energy (heat, light, motion, etc.).
Electrical energy is usually sold by the kilowatt hour (1 kW·h = 3.6 MJ) which is the product of the power in kilowatts multiplied by running time in hours. Electric utilities measure energy using an electricity meter, which keeps a running total of the electric energy delivered to a customer.

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1. ### Minimizing the voltage drop across a capacitor (solution shown)

The following is the question and the solution to the question. I understand the solution to the part where you find the Ceq and derive Qeq from the equation Q = Ceq*V. However, I do not understand where V1 = V0-V2 come from. When calculating the minimum voltage, how do you come up with the...
2. ### B Magnetic pendulum and electric energy....

While reading about electromagnetism from the OpenStax books with my son (and doing some experiments), he asked this question. Suppose I hang a pendulum and make it oscillate inside a coil connected to a Galvanometer as shown in the schematic diagram: Hopefully the image is clear enough. His...
3. ### Electric energy density in the dielectric of a coaxial cable

V(ρ) = V_o*ln(ρ/0.0018)/ln(45/180) (Attached picture is where the unit vector of r is really ρ.) In cylindrical coordinates ∇V = ρ*dV/dρ + 0 + 0 ∇V =derivative[V_o*ln(ρ/0.0018)/1.386]dρ ∇V = V_o*0.0018/(1.386*ρ) E = V_o*0.0012987/ρ Work = 0.5∫∫∫εE•E dv Bounds: 0.0018 to 0.00045 m D = εE =...
4. ### New materials and ways to store electric energy

Hello everyone ! I'm Hugo. I'm a french high school student. This year I've a project on new way to store electricity and their materials.I've done researches on super capacitors. But I've found only that "new way" to store electric energy. And for the material part, I don't know what I can...
5. ### Electrostatic energy after a metal piece is inserted between 2 capacitor plates

Homework Statement fig 1 : Area of each plate is S, separated by 2d, charge Q in the capacitors fig 2 : uncharged conductors of area S, thickness d, inserted parallel between plates What is the ratio of electrostatic energy in fig 2 to electrostatic energy in fig 1? Homework Equations Q =...
6. ### Can electric energy be directly measured?

I expect that power monitors directly measure the current, voltage change, and maybe phase to directly calculate current power use. Can electric energy directly be measured, or do meters just calculate power, and integrate it to obtain energy?
7. ### Electric Energy: How is it Gained and Lost in Electricity?

In most textbooks the electric energy is merely mentioned, not explained. From a google search the definition states that electric energy is the movement of electrons. But what exactly is it? It is obvious that it does work by transferring the potential energy to kinetic energy. So is electric...
8. ### How Do You Calculate Electric Energy Density Near a Copper Wire?

Homework Statement Calculate the electric energy density at the surface of a 3.4 mm diameter copper wire carrying a 28 A current. Homework Equations u = (1/2) ε0 E2 The Attempt at a Solution With the electric energy density equation, I substituted in the equation for the electric field for an...
9. ### How do integrals actually work?

Homework Statement Calculate the electrical energy required to assemble a spherical volume of radius R and charge Q, homogeneous density ρ the answer is (3/5)Q/R the textbook says you have to build the volume integral one layer of sphere at a time, I'll get back to that later. I like...
10. ### Questions about electric fields, voltage and electric energy

1. If e.m.f is NOT a force, but actually energy – and e.m.f is measured in Voltage – then why is p.d. (V) NOT used up? Since we know energy *does* get used up by the component. I know the electrons are just the medium – energy carriers – but Voltage doesn’t mean number of electrons; it means...
11. ### Limit on mechanical & electric energy conversion efficiency

I regret to say that I know little of engineering, but, to make a long story short, I'm nagged by two questions about energy conversion efficiency. There is a thread i made titled "giant railguns recycling their own energy in space" in the science fiction & fantasy forum here that explains my...
12. ### Physics 12 Electric Energy Question

Homework Statement A proton starts at rest and travels through a potential difference of 8000V. What's it's final speed. Homework Equations ΔEe+ΔEk=0 ΔEk=-ΔEe Ee=qV The Attempt at a Solution I know how to find the correct magnitude, but I am getting the wrong sign. Ek=-ΔEe 1/2mv^2=-qΔV...
13. ### Calculating Final Voltage in Capacitor Discharge: What Could be Wrong?

Hi All, (First post, be nice). I'm analysing the discharge of a capacitor. Starting from the energy in a capacitor: E = \frac{1}{2} CV^2 This can be represented as follows (seen this elsewhere, there is nothing wrong with this): \Delta E = P \Delta t = \frac{1}{2} C(V^2_s-V^2_f) Where \Delta...
14. ### Using 8 Mega Volts DC as electric energy source?

If a fusion reactor could be constructed that runs on Li-7 and hydrogen, and if the energy produced by that reactor where extracted with a direct charging setup, like in a nuclear battery emitting alpha particles, the voltage produced would be the stupendous voltage of 8 mega volts. Now, how do...
15. ### Relationship between electric energy and force

Homework Statement One of the three types of radioactive decay is "β decay", during which protons decay into neutrons or viceversa, emitting either electrons (β) or positrons (β+) at high velocity as a result. In one experiment, a β source and β+ source are placed 10 cm apart from each other...
16. ### Electric energy from thermocouples

If I were to make millions of contacts or "spots" on a long wire,and connect them in series(or parallel?),then make half of them warmer than the other half,would I get any useful voltage,i.e. electrical energy I could use to power something?
17. ### Oil Drop Electric Field Problem

Homework Statement An oil drop is charged negatively. How much charge is on the drop if the Electric Field is 6,400 N/C at a distance of 1.2 m? Homework Equations E=k q/r^2 I don't know if I should be using that equation for this one. The Attempt at a Solution I tried to do E/(k x r^2) = q...
18. ### Magnetic Lift & Earth's Magnetism: Exploring Possibilities

Hello, I have an idea i have been working on for some time. I am a meteorologist and pilot, and i love aviation, especially design. I have been playing with the idea of magnetic lift (as in when one magnet is repelled from another magnet) or electromagnetism in an engine, to create a different...
19. ### A rectangle with Charges on Each Corner - Find Missing Charge?

Homework Statement A charge is to be placed at the empty corner of a rectangle to make the net force at corner A point along the vertical direction. What charge (magnitude and algebraic sign) must be placed at the empty corner if the three charges have the same charge of +8.45 μC?Homework...
20. ### Internal resistence: chicken and egg misconcpetion

I feel like have a chicken and egg type of problem regarding internal resistences because of the following problem: The voltage across a battery with internal resistence is given by the equation EMF-Ir=V Given the voltage across the battery then the voltage in the circuit is V=IR So, if I have...
21. ### Reversing/Weakening a Permanent Magnet's Field: A Mystery?

Found one article saying it is possible to reverse poles of permenant magnet using coiled wire wrapped around magnet, but nothing about the possibility of temporarily reversing or even temporarily weakening the magnetic field.. if there are any magnetism connoisseurs out there..
22. ### How Does Electron Shape Affect Electric Field Energy?

Homework Statement a. Calculate the energy density of the electric field at a distance r from an electron (presumed to be a particle) at rest. b. Assume now that the electron is not a point but a sphere of radius R over whose surface the electron charge is uniformly distributed. Determine the...
23. ### A question about electric energy

Hi guys I know that in a 6 volt battery 1 columb of charges gain 6 joules of energy do they gain potential or kinetic energy as they move from the negative terminal to the positive terminal ? And how different the energy in Ac electro motive force
24. ### Electric Potential and Electric Energy

Homework Statement Consider point a which is 65 cm noth of a -2.8μC point charge, and point b which is 80 cm west of the charge. Determine (a) Vba=Vb-Va, and (b) Eb-Ea (magnitude and direction)Homework Equations k=9x10-9 V=kQ/r V=kQ(1/rb-1/ra) E=kQ/r2 E=kQ(1/rb2-1/ra2)The Attempt at a Solution...
25. ### Different equations for Electric Energy, me understand

I've been reading recently about Electric Potential Energy and when introduced with the following situation of two charged plates (one (-) and the other (+)) and a charged particle between them I've been taught the following equation. a) U=E/Q ⇔ E=QU However now when I'm reading about a...
26. ### Calculating Electron Speed and Energy in a Parallel-Plate Apparatus

Homework Statement An electron is released from rest from the negative plate of a parallel-plate apparatus, what is the electrons speed one third of the way between the plates. It also asks for the speed at which electron will hit the positive plate if a 450 V potential difference is applied...
27. ### Change in Electric Energy of Spheres

Homework Statement A heavy nuclei can be approximately considered as a spherical ball with uniform volume density  = 4/3 * 10^ 25 C/m3. If a nuclei with total charge Q = 92e splits into 2 equal spherical piece and they fly away. What will be the total electric energy change during this...
28. ### Using water to create electric energy

Could a small amount of water be made somehow to create enough electric current to make a small heater bar hot or to even warm up?
29. ### Simple electric energy detectice device for home

Hi, I'm now in the project research to design a simple low cost and ease installation electric energy detective device. My idea is to put the sensor (etc..) in or within distribution board. Also the device can alarm consumer if they are using more energy. Just want the opinion from you...
30. ### Electric Energy Potential and Capacitors

Homework Statement So this is from a past test put up as a study guide, but I'm stumped here. The question is: A spark jumps between two electrodes, transferring a charge of 5 μC in 2 × 10−3 s. The constant current I that would transfer the same charge in the same time is The Attempt at...
31. ### Conversion of Electric Energy in Resistors

Hello, I was wondering if someone here could confirm or explain what happens in a resistor. My assumption is that when the electrons enter a resistor, they slow down, thus decreasing the strength of the electromagnetic field and causing the excess energy the field can no longer hold to be...
32. ### Electric field, Electric Potencial, Electric Force, Potential Electric Energy

Hi, I have some questions about these concepts. The equations: Electric field =\frac{K.|Q|}{d^2} Electric potential =\frac{K.|Q|}{d} Electric Force =\frac{K.|Q|.|q|}{d^2} Potential Electric Energy =\frac{K.|Q|.|q|}{d} Electric field and electric force are vectors, electric...
33. ### Point charges and potential electric energy

This is probably child's play for most of you, but a guy like me struggles to understand basic concepts. A kick in the pants to set me off in the right direction would be greatly appreciated. Homework Statement How far must the point charges q_1 = 7.60 microCoulombs and q_2 = -24.0...
34. ### Electric energy - potential difference problem

Homework Statement On planet Tehar, the free-fall acceleration is the same as that on Earth, but there is also a strong downward electric field that is uniform close to the planet's surface. A 2.00 kg ball having a charge of 5.00 µC is thrown upward at a speed of 20.1 m/s. It hits the ground...
35. ### Electric Energy Storage at Superconducting Temperatures?

Is it Theoretically possible to build a superconducting motor/generator/energy storage device all at superconducting temperatures? The device needs to operate in vacuum, accelerate and decelerate with only field energies exiting the vacuum chamber. I don't have much faith in batteries at 4oK...
36. ### Electric energy in a capacitor

Homework Statement part 1. Consider a simple RC circuit consisting of a resistor and a capacitor connected in series to a battery. The resistor has a value of 8kOhms, and the capacitance is 3uF. The final (asymptotic) value of the charge in the capacitor is E*C. At what time is the charge...
37. ### HELP A problem on electric energy storage

HELP!A problem on electric energy storage Homework Statement when two capacitors are connected in parallel and then connected to a battery, the total stored energy is 5.0 times greater than when they are connected in series and then connected to the same battery. What is the ratio of the two...
38. ### Electron/proton kinetic electric energy

Homework Statement an electron starting from rest acquires 3.53keV of kinetic energy in moving from A to B. how much kinetic energy would a proton acquire moving from B to A. Homework Equations 1/2mv2 me=9.11e-31 kg mp=1.67e-29 kg 1eV=1.6e-19 J The Attempt at a Solution...
39. ### Converting Watts to Volts: Maximum Current for a 3.5W Resistor

What is the maximum current allowed in a 3.5 W, 220 ohm resistor? The answer needs to be in amps so how would I convert watts to volts?
40. ### Electric energy stored in dipole

there is a +q and -q on the x-axis. the +q is L/2 in the negative direction and the -q is L/2 in the positive directions. the distance between the two charges is L. there is a test charge P on the y-axis a distance r from both charges. we had to find the electric energy stored in the dipole...
41. ### Electric energy stored in a vacuum

Hi, I've had this question in my mind for a long time.. When we say that the electrical energy stored in a vacuum is U=1/2\epsilon0*E^2, we assume that the energy is stored in the electric field right? But physically what does that mean? For eg: In a dielectric one can say that the energy...
42. ### Electric Potential / Electric Energy

Homework Statement A 0.50kg ball is suspended in a uniform electric field ( E = 1500 N/C ) as shown in the diagram ... http://img201.imageshack.us/img201/9771/23vl0.th.png Calculate the charge on the ball Homework Equations The Attempt at a Solution I found fg = -4.9 N...
43. ### Essay Question on Potential Electric Energy

If the electric field is 0, then is the electric potential 0? If the Electric pottential 0 then is the electric field 0? Explain why or why not. .. I rather say my idea on this topic, this my first post I am rather shy...:frown:
44. ### Finding Electric Energy Density

Homework Statement Find the electric-field energy density at a point which is a distance of 10.0 cm from an isolated point charge of magnitude 7.30 nC. Homework Equations u = \frac {1} {2} * e_{o} * E^{2} The Attempt at a Solution u = \frac {1} {2} * 8.85*10^{-12} * 7.30^{2}...
45. ### Electric Energy and Spring Constant Problem

Homework Statement Two spheres are mounted on identical horizontal springs and rest on a frcionless table, as in the drawing. When the spheres are uncharged, the spacing between them is 0.0500 m, and the springs are unrestrained. When each sphere has a charge of +1.60 microC, the spacing...
46. ### How many joules of electric energy are there in 1 kilowatt-hour?

How many joules of electric energy are there in 1 kilowatt-hour?
47. ### Electric Energy: False Claims Debunked

When electric charges occur in a system, it is possible to determine the electric energy of the system. Which of the following is false: d. The electric energy of the system can only vary when it is converted into thermal energy Why is this answer False? What other factors affect...
48. ### Heat energy to Electric energy?

Is it possbile to covert heat energy (like that from the surface of a hot radiator) to electric energy? Whats the theory behind this? --thank you.
49. ### Electric energy of a dielectric sphere

Electric energy of a dielectric sphere! Hi there, I have attempted a question, I was just seeing if some one can go over it and check if it is ok! Q. The Electric field E inside a dielectric sphere placed between the plates of a large parallel-plate capacitor is uniform. Given that the...
50. ### Controled electric energy extraction from clouds

When someone mentions exploatation of an electric (electrostatic) energy from clouds one would instantaneously imagine a gigantic capacitor (or some other sort of an "acumulator" for such energy) and a loud BANG(!) when thunder strikes it and polirizes it all at once; but isn't it possible to...