Electric charge Definition and 274 Threads

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charge: positive and negative (commonly carried by protons and electrons respectively). Like charges repel each other and unlike charges attract each other. An object with an absence of net charge is referred to as neutral. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that do not require consideration of quantum effects.
Electric charge is a conserved property; the net charge of an isolated system, the amount of positive charge minus the amount of negative charge, cannot change. Electric charge is carried by subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the nuclei of atoms. If there are more electrons than protons in a piece of matter, it will have a negative charge, if there are fewer it will have a positive charge, and if there are equal numbers it will be neutral. Charge is quantized; it comes in integer multiples of individual small units called the elementary charge, e, about 1.602×10−19 coulombs, which is the smallest charge which can exist freely (particles called quarks have smaller charges, multiples of 1/3e, but they are only found in combination, and always combine to form particles with integer charge). The proton has a charge of +e, and the electron has a charge of −e.
Electric charges produce electric fields. A moving charge also produces a magnetic field. The interaction of electric charges with an electromagnetic field (combination of electric and magnetic fields) is the source of the electromagnetic (or Lorentz) force, which is one of the four fundamental forces in physics. The study of photon-mediated interactions among charged particles is called quantum electrodynamics.The SI derived unit of electric charge is the coulomb (C) named after French physicist Charles-Augustin de Coulomb. In electrical engineering it is also common to use the ampere-hour (Ah). In physics and chemistry it is common to use the elementary charge (e as a unit). Chemistry also uses the Faraday constant as the charge on a mole of electrons. The lowercase symbol q often denotes charge.

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  1. S

    Electric Charge in a Magnetic Field

    1) For a particle of mass m and a charge of q moving in a circular path in a magnetic field B, show that its kinetic energy is proportional to r^2, the square of the radius of the curvature of the path. I started off with the definition of KE: (mv)^2/2 and the fact that a = v^2/r, where F =...
  2. F

    Total Electric Charge: Is Our Universe's Zero?

    Do you think the total electric charge of Our Universe is zero?
  3. F

    Electric charge, creating plasma and keeping it apart

    if you have a device similar to a stun gun, with a spark continuously jumping across the 2 contact points. electric field has to rip electrons from the air moecules leaving positive ions - creating plasma. now imagine you have a negatively charged disc nearby the device which is covered in a...
  4. C

    2 Electric Charge Particles w/ acceleration?

    Hi all, I am having trouble on where to start w/ this problem: Two equally charged particles, held 3.0 10-3 m apart, are released from rest. The initial acceleration of the first particle is observed to be 7.0 m/s2 and that of the second to be 10.0 m/s2. The mass of the first particle is...
  5. S

    Where Can a Third Charge Be Placed to Cancel Out the Electrostatic Force on q_2?

    I need a bit of help with two problems. I've just started using latex, so bear with me if the equations are a bit funky. The charges and coordinates of two charged particles held fized in the xy plane are q_1 = +3.0 * 10^(-6) C and (0.035, 0.005) and q_2 = -4.0 * 10^(-6) C and (-0.02...
  6. M

    Electric Charge Oscillation & Light Waves

    If an moving electric charge produces light waves what is it is oscillating?
  7. G

    Electric Charge and Help Putting an Answer Into CAPA Assignment

    I'm using CAPA now for online homework and I seem to be having some trouble inputting an answer. Last semester I used webassign which I think is so much easier. Anyways, the first question was "Two small spheres with charges 7 and 6 coulombs are held 9 m apart. Find the magnitude of the force...
  8. T

    Can electric charge be enclosed ?

    Hi everybody I'm wondering if it is possible to enclose a relatively high electric charge in a non-conducting recipent (say plastic or glass -- macroscopic : centimeters) ? Is it possible technically ? if so, what is the limit amount of charge we can enclose ? if so, would the recipient...
  9. G

    Does an electric charge curve spacetime ?

    Does an electric charge "curve spacetime"? If theorists (starting with A. E.) can make a theory about spacetime curvature caused by mass (GR), couldn't there be a similar theory where some spacetime curvature is caused by electric charges? Both are F = k/r^2 in elementary physics. A...
  10. H

    Find the total electric charge

    I am confused by a question related to me about electric charge. How can you find the total electric charge of 1 kg of an electron or proton? I know the magnitudes of the charges are + - 1.60X10^-19 C. Would I use the, for example, the electron mass 9.11X 10^31 kg, take the 1 kg and divide by...
  11. P

    What is the force at 18 degrees in a charged ball suspension problem?

    two identical, equally charged balls are suspended from strings 0.25 in length from a single point. The mass of the ball is 8e-4kg. The strings spread 36 degrees. The problem asks to find the charges. My question is what should the force be when moving the ball at 18 degrees?Is it F at full...
  12. marlon

    Why is Electric Charge Quantized?

    This is why electric charge is quantized. See the zip-file if this word-doc regards marlon
  13. C

    How to Solve Electrostatics Problems Using Coulomb's Law

    Hi, I'm seeking help with a couple of problems involving electrostatics. Q1)Calculate the electric field at the centre of a square 0.1m on a side if one corner is occupied by a charge 0.2micro C, and the other three corners are occupied by the charge of -0.9micro C Q2) A positive test...
  14. K

    What is the Relationship Between Quark Size and Electric Charge?

    When I use the following equation which assumes quarks are spheres of charge and compressing the spheres creates mass (by doing work): mass of quark = integral of ( k q ^2 / r^2 c^ 2 ) d r and input masses from the mass equation I arrived at by trial and error a few months ago Mass =...
  15. U

    Dimension of the electric charge

    could someone told me an experiment that ı can find the dimensions of the electric charge in therms of m, kg, sec the answer is kg^(1/2)*m^(3/2)/sn it can be found by assuming the epsilon zero is dimensionless please say me an experiment that i can check it :confused: :confused:
  16. Antonio Lao

    Unlock the Concept of TOE: Electric Charge & Mass

    Two keys that will help anybody seeking TOE. 1. The key of complete understanding the concept of electric charge. 2. The key of complete understanding the concept of mass. The 1st key does have a lot of supporting direct evidence for its existence. The evidence for the second are mostly...
  17. U

    Why electric charge is attracted to the earth (ground) ?

    Anybody know why electric charge is attracted to the Earth (ground) ?
  18. R

    Electric charge and Electric Field

    [?] I am working out of the Physics Fifth Edition by Giancoli, I am having trouble with Chapter 16, questions 19,29 and 49. I took Physics One about 6 years ago and can't seem to remeber the basics to figure these problems out. Can anyone help me? Thanks, Ron
  19. D

    Electric charge and fields: uniform electric field

    A force of 6N acts on a charge of 3 microC when placed in a uniform electric field. what is the magnitude of the electric field? I have E = k(Q/r^2... k=9x10^9 * (Q,charge=3x10^-9) / (?)^2 ths can't be the right formula caus e wheres r^2? Dx [?]
  20. D

    How Do Electric Charge and Fields Influence Forces and Charges?

    Hello, I have some missed test questions that I still don't understand. Can anyone please explain these. 1) Two chrged objects atrract each other with a force F. What happens to the F between them if one is doubled, the other is tripled and the separation distance between their centers...
  21. D

    What is the charge on 1kg of protons?

    This one stumps me cuase not a lot of info. what is the charge on 1kg of protons? Thats it, i swear! no more info to give you guys so we can try to solve. Do you know how to help me, please? Thanks! Dx :wink:
  22. D

    Electric charge and elctric filed

    Hiya! Whoa! vectors, i hate those stinkinh vectors! :wink: Anyways, I have theis problem and don't know how to solve for it. A piece of plastic has a net charge of +2.00 microC. How many more protons then eclectrons does this piece of plastic have? Now i know plastic is a insulator...
  23. Tyger

    Electric Charge, a novel view.

    I may edit this post considerably so if it interests you, you may want to recheck it from time to time. Two of the most interesting questions in Physics relate to the value of Electric Charge. Why is it's value quantized and why does it have the particular value of appr. 1/137? This is not an...
  24. D

    Geometry and Surface Density of Electric Charge

    I have never seen an explicit formula to describe the relation between charge density and geometry (e.g. local curvatures) of the surface of a conductor. We all know that charge tends to accumulate at edges (high curvature) but can we be more quantitative? Hope someone else will find this...
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