What is Charges: Definition and 1000 Discussions

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.

View More On Wikipedia.org
  1. B

    Calculating Centripetal Force for Particle in Circular Motion

    A particle of charge Q is fixed at the origin of an xy coordinate system. At t = 0 a particle (m = 0.694 g, q = 5.04 µC is located on the x-axis at x = 20.2 cm, moving with a speed of 34.0 m/s in the positive y direction. For what value of Q (in μC) will the moving particle execute circular...
  2. S

    Point Charges and Static Electricity Problem

    Hi! I am having a tough time with this question, and would just like some clarification if that's at all possible! I feel I may just be missing a key concept, however, any help is appreciated! Thanks. Homework Statement Point x is .25 m away from a point charge of +4.7*10^-8 C, point Y is...
  3. M

    Finding the energy field due to three positive point charges on a 4th negative charge

    Homework Statement Three equal positive point charge of magnitude Q=7.00uC are located at three corners of a square of edge length d=4.8cm. A negative charge of -21.00uC is placed on the fourth corner. A) At the position of the negative charge, what is the magnitude of the electric field due...
  4. C

    Point Charges on Equilateral Triangle - Need Geometry Help

    Homework Statement http://www.ridemtl.com Homework Equations F = k(q1q2/r^2)The Attempt at a Solution I know pretty much what to do for the problem, but I cannot get the right answer. I think my issue lies within what angles I am using for the components. Because it is an equilateral triangle...
  5. L

    Induced charges and electrostatic potential

    There is one point I am unclear upon in terms of indued charges. If a charge is induced by another charge, will the potential from the induced charge have an effect on the inducing charge. It seems that if it were the case you would be getting (increasing) energy from nothing, however if it...
  6. J

    What is the equation for calculating the electric field and charges?

    Homework Statement http://imageshack.us/photo/my-images/94/mphelp.jpg/" Homework Equations coulomb law The Attempt at a Solution no idea.. maybe other E field is -0.3 to cancel it out?
  7. A

    Equillibrium of electrostatic forces of 2 charges on a 3rd

    Homework Statement Two particles lie on the x axis. The first particle is at the origin with a charge of +1.6uC and the other has a charge of -3.1uC and is +10.5cm away. If particle 3 of unknown charge q3 is to be located such that the net electrostatic force on it from particles 1 and 2...
  8. B

    Solving Two Point Charges: Electric Field, Dipole Moment & Potential Energy

    Homework Statement Two point charges q1 = 2\muC and q2 = -2\muC are placed at r1 = (3,0,0) m and r2 = (0,0,4)m respectively i) What is the force of q1 (in vector form)? ii) What is the electric field at the origin? iii) What is the electric dipole moment of this arrangement (in vector...
  9. N

    Calculating the work done to bring charges together

    Homework Statement How much work is required to assemble eight identical point charges, each of magnitude q, at the corners of a cube of side s? Note: Assume a reference level of potential V = 0 at r = infinity. (Use k_e for ke and q and s as necessary.) Homework Equations V = E.s U = q.V V =...
  10. F

    Free Charges in a Dielectric Sphere

    Why is it that a dielectric sphere containing free charges, uniformly distributed throughout, has a net electric field? If the sphere is electrically neutral, then all the charges should cancel out, and since the free charges are uniformly distributed, I don't understand why there should be an...
  11. R

    Point charges, midpoint zero or non zero?

    Homework Statement Point charges +q and -q are placed at +50 cm and -50 cm on the x-axis, respectively. Is the electric field at the origin (halfway between the charges) zero or nonzero? If nonzero, which direction does it point? Homework Equations The Attempt at a Solution Well...
  12. S

    Interaction between charges in motion

    In order to explain the relativistic nature of magnetism, a book shows an example of linear procession of charges: positive charges in one direction and negative charges in the opposite one. It says that this is equivalent in the reality to a not charged current carrying wire. In a metallic wire...
  13. E

    Electric charges, wrong answer D: ?

    Homework Statement Find the net force at point A q1=-6x10^-5 C q2=-3x10^-5 C q1 is 3m north of A q2 is 3m east of A find the net force on a -1.2x10^-5 C charge The Attempt at a Solution first off I find how the electric field is with no charge at point A = 6.7 x 10^4...
  14. N

    Charges , electric potential

    Hi , am a computer science student , am newbie at physics , and am train to learn but no help , though i took a course in [physics 1] before 3 yrs and i can't remember anything, and now i am taking physics 2 , i took so far , electric fields , Gauss law ,Electric potential , capacitance . book...
  15. G

    What is a Point Charge and How Does it Work?

    What is a point charge? I have read wikipedia but m not much satisfied... please can you explain me in your own words? thanks
  16. K

    Finding Charges in Battery for 5 Seconds

    Homework Statement The e.m.f of a battery is 12V and provides an electrical energy of 500J. What is the amount of charges flowing in the battery for 5 seconds? 2. The attempt at a solution Since V=W/Q, rearranging the equation gives you Q=W/V: Q= 500/12 = 41.6666667 C But, I don't...
  17. C

    E & B Fields from Moving Charges: The Magnetic Monopole Mystery

    Lets say I have a negative line charge on a long thin rod, if I am at rest with respect to that rod I will see an E field. But If I am moving with respect to that rod I will see a B field. So why are people looking for magnetic monopoles, If B fields are E fields in disguise, wouldn't the...
  18. zimo

    B field at the center of a large charges sheet

    Homework Statement In a plastic film factory, a wide belt of thin plastic material is traveling between two successive rollers with the speed v. In the manufacturing process, the film has accumulated a uniform surface electric charge density σ. What is B near the surface of the belt in...
  19. K

    Finding the magnitude of the electric field from 3 charges at a point P

    Homework Statement Hi, here is the problem I'm having trouble with: Three charges Q1, Q2, and Q3, each equal to 6.4 × 10–19 C, are in a straight line. The distance between neighboring charges is 60 nm. Find the magnitude of the electric field at P, which is 80 nm from Q2 on a line at right...
  20. P

    Why field lines must begin or end on electric charges?

    Homework Statement Use Gauss' law to explain why field lines must begin or end on electric charges. Homework Equations Gauss' law: \epsilon_0 \phi_E=q The Attempt at a Solution I'm not sure whether this solution is incomplete or inconsistent. First, I take a gaussian surface...
  21. A

    Induced voltage of magnet of two like charges

    Homework Statement 1. compare the induced voltage of the attached magnet ( two like charges) with the induced voltage of one magnet only? 2.compare the induced voltage of attached magnet (opposite poles) with one with only one magnet Homework Equations The Attempt at a...
  22. AJKing

    [Intro Chemisty] Positive and negative charges.

    I'm just learning but I can almost SWEAR that this is right, just reassure me?
  23. K

    Force Experienced by Charges between Parallel Plates

    Hello, Is the force experienced by a charge at any point between two charged parallel plates the same? Just a preliminary step to my homework question, Let's say I have two parallel charged plates. (positive on top and negative on bottom with field lines going downwards.). Would all positive...
  24. K

    Can permanent magnets be modeled as set of magnetic charges ?

    Can permanent magnets be modeled as set of "magnetic charges"? Computing the full magnetic field of a permanent magnet and what forces two permenant magnets exert on each other is obviously a field theoretic problem that requires a solve using e.g. a FEA method or simular. For two idealized...
  25. L

    Coulomb's law with more point charges than one

    Hi everyone, I got a little question. Let's say we have 3 point charges on a line, for example on the x axis. 1----2----3 something like this. If I want to calculate the Force on point charge one, why am I allowed to just add the forces 12 and 13. I saw it in a book and was confused...
  26. O

    4 Charges at the corners of a square

    Homework Statement Consider a square which is 1m on a side. Charges are placed at the corners of the square as follows: +4 uC at (0,0) +4 uC at (1,1) +3 uC at (1,0) -3 uC at (0,1) What is the magnitude of the electric field at the square's center? Homework Equations E=...
  27. M

    Electrodynamics- energy required for 2 charges approaching

    Hi guys, I have a quick q about solving questions where there are two charges q1 and q2 approaching each other (in this textbook problem it is from 0.1 m to 0.01m). I understand that you have to keep one of the charges stationary and use the formula: W=q(Vf-Vi) = q1[ (k*q2)/r2 - (k*q2)...
  28. M

    Charges mass on the end of a light string

    Homework Statement A charged mass on the end of a light string is attached to a point on a uniformly charged vertical sheet (with areal charge density 0.25 μC/m2) of infinite extent. Look at attachment for diagram Find the angle \theta the thread makes with the vertically charged...
  29. R

    Electricity and magnetism point charges problem

    Homework Statement Four point charges have equal magnitudes. three are positive and one is negative, as the diagram shows. they are fixed in place on the same straight line, and adjacent charges are equally separated by a distance d. consider the net electrostatic force acting on each...
  30. J

    Properties of electric charges - insulators and conductors

    Homework Statement I have some hypothetical questions. Question 1 There is a conductor with a single electron and proton inside of it. If we try to charge the conductor by induction, we might put a proton close to the conductor. The electron will go towards that proton while the proton in...
  31. B

    Self Energy of Charges: Explained

    can somebody explain about this self energy??
  32. C

    Accelerating Charges & Light: Massless Particles

    If accelerating charges emit light. Then would this imply that mass less particle could not emit light because they cannot accelerate?
  33. M

    Inducing a current through moving charges or electromagnetic radiation

    I have recently found a circuit schematic that can pick up radio signals without the need of a battery. Is this an example of electromagnetic induction? If so, how much voltage/current is induced? Does it change the properties of the electromagnetic wave, e.g. energy, wavelength, etc...
  34. P

    Virtual particles and screening of charges

    I'm reading The Lightness of Being by Frank Wilczek. In a footnote talking about screening of a (real) positive charge by virtual particles (p47), he says "Thus the force falls off faster than 1 over the distance squared, as you'd have without screening" (by virtual particles). How then...
  35. O

    How to divide positive and negative charges from each other

    How to divide positive and negative charges from each other without them interacting with other matter or charge patterns. ,please answer I only need this to make my ultimate machine
  36. J

    Understanding Electric Field Direction Around Point Charges

    I don't know, when given a point charge (sign is indicated = positive or negative), which direction the field lines go Although I NOW know that if the point charge is positive, field lines are outwards, and if negative then they are inwards...HOWEVER, I have come across an example or two...
  37. G

    Interaction of two point charges

    I'm trying to get a deeper understanding of how two particles such as protons interact with each other. In high school physics, I was told that they give off a field, which is felt by the charges, and then repels them. My first question is, if I fire two protons at each other head on (lets...
  38. L

    Buying a New Car Tag in Florida: Dealer Charges & Fees

    The dealer where I bought my car is charging me 370 dollars to get my new tag for my new car. How much of that money is going towards the actual tag and how much are they taking out? I live in Florida. I tried looking on the DMV website and that's pointless. I saw no information that will help...
  39. A

    Assignment question, two charges electric field

    Homework Statement Two charges q1 and q2 are 11cm apart and have an electric force between them of 6e-6N. If the charge on q2 is increased by 12 times and the distance between q1 and q2 changed to .44cm, what is the new electric force between these charges? q1 ? q2 ? distance (1) 11cm...
  40. L

    Finding Equilibrium Charge in a Static System

    Homework Statement In the figure below the charge in the middle is Q = -4.6nC. For what charge q1 will charge q2 be in static equilibrium? q1-----10cm------Q------10cm------q2 I know that the answer is supposed to be 18nC. Homework Equations F=Ke lq1llq2l/r2 The Attempt at a Solution...
  41. P

    Image charges of a 30 degree corner

    Homework Statement I just want to make sure I'm doing this right. okay so you have a conducting corner of angle 30 degrees. How many image charges are there, I just need to sketch it. Homework Equations The Attempt at a Solution my book sucks only explaining it for a 90 degree...
  42. C

    Accelerating Charges: Electron on Earth & Light Emission

    If standing on Earth and being accelerated by a rocket out in space at g are the same thing, Or at least have the same effects. And if accelerating charges emit light then would an electron sitting on Earth emit light? But I don't see how this is possible because where would the energy come from.
  43. K

    Minimum Work Needed to Bring 2 charges from distance infinity

    Two charged particles are brought together from a great distance (r=infinity) to a distance of 2 m. The particle has a positive charge of 3.0 x 10^-5 C and the second has a negative charge of 1.35 x 10^-5 C. What minimum work was accomplished in this process? I can't for the life me figure...
  44. N

    Two point charges with electric potential energy?

    Homework Statement "Two point charges 2.0cm apart have an electric potential energy -180 microJoules. The total charge is 31 nC. What are the two charges?" Homework Equations V= k * q / r The Attempt at a Solution I understand that V = -180 * 10^-6, k = 9*10^9, r = 0.02m, and the...
  45. A

    Net Electric Force on +q Charge with Two Added Charges

    Homework Statement Two more +Q charges are held in place the same distance "s" away from the +q charge as shown. Consider the following student dialogue concerning the net force on the +q charge: The two added charges are written with blue Q's Student 1: "The net electric force on the +q...
  46. A

    Gauss' Law and charges placed within a spherical conductor

    Homework Statement A hollow sherical conducting shell is suspended in air by an insulated string. The total charge on the conductor is -6 microCoulombs. If an additional point charge of +2 microCoulombs is placed in the hollow region inside the shell what is the total charge induced on the...
  47. R

    Find Dielectric Constant Given Charges

    Homework Statement When a certain air-filled parallel-plate capacitor is connected cross a battery, it acquires a charge (on each plate) of 130 μC. While the battery connection is maintained, a dielectric slab is inserted into and fills the region between the plates. This results in the...
  48. F

    Problem on distribution of charges between charged/uncharged spheres

    Homework Statement 2 Spherical conductors B and C having equal radii and carrying equal charges repel each other with force F. Another conductor A having same radius as B but uncharged is brought into contact with B, and then C and then removed from both. Find the new force of repulsion...
  49. E

    Force between two point charges

    Homework Statement Two positive point charges are 4.60 cm apart. If the electric potential energy is 75.0 x 10^-6 J, what is the magnitude of the force between the two charges? Homework Equations U=kq/r (1) F=kqq/r^2 (2) The Attempt at a Solution So I tried using (1)...
  50. F

    Electrostatics of 4 charges arranged in a square

    Homework Statement Four charges are arranged on the corners of a square whose edge length is a. Two positive charges +Q are placed on diagonally opposite corners, and two negative charges -Q are placed on the other corners. (a) What is the force on a test charge qo placed at the center of the...
Back
Top