Charges Definition and 1000 Threads

  1. G

    Combined Electric field for two charges using electric potential

    Homework Statement Two equal and positive point charges Q1 and Q2 are a distance d from each other on the x-axis. Find the electric potential at the point P which lies a distance z on the z-axis from their centre. Then find the Electric field at the point, and then find the force F on a...
  2. R

    Coulomb's Law, what charge will make the two charges in static eq.

    Homework Statement In the figure below the charge in the middle is Q = -3.7 nC. For what charge q1 will charge q2 be in static equilibrium? Homework Equations F = (K*q1*q2)/(r^2)The Attempt at a Solution I'm not sure where to go after acknowledging that Fq1->q = -Fq2->q
  3. B

    0 Electric potential between point charges?

    Can someone explain how you can have a zero electric potential between opposite charges? a charge would move there. I thought electric potential was the measure of energy per charge. wouldn't a 0 electric potential imply that a test charge cannot have any potential energy at this point? how is...
  4. K

    Quick question, eletric field of a conducting sheet of charges

    Hi one quick question about the electric field of a conducting sheet of charges. When you given a horizontal sheet of conductor with uniform distributed charge on its surface,will there be any electric field on the top AND on the bottom of the sheet? How is that different from a...
  5. L

    Capacitator Circuit and determining unknown charges voltages

    Homework Statement Suppose in the figure (Figure 1), that C1 = C2 = C3 = 18.0μF and C4 = 28.2μF. If the charge on C2 is Q2 = 37.4μC, determine the charge on each of the other capacitors Determine the voltage across each capacitor. Determine the Voltage Vab across the entire...
  6. R

    Electric Force of charges A,B,C on another charge

    Homework Statement A, B and C have charges of -2.6, 8.5, and 7.5 microC respectively. These charges are at the points 2.5, 7 and 2 on a straight line where all distances are measured in millimeters from the zero point. What force does a -7.5 microC charge feel if it is at the point 1.2 mm...
  7. E

    Finding Electric Field of Two Charges

    Homework Statement There is a charge Q=1 μC located at x=0 and a charge -Q/2 located at x=4 m. What is the E-field. At what value of x is the E-field zero? Express your answer in meters and do not approximate decimals digits. Homework Equations E=\frac{q_1 q_2 k_c}{r^2} Removing...
  8. J

    Kinetic energy and speed of system of charges (electric potential)

    Homework Statement A square of side s has a point charge at each corner. They all have the same charge +q, but different masses, m1, m2, m3, and m4, respectively. Initially, all of the charges are held at rest until they are released. Of course, they would repel each other and move away from...
  9. M

    Three Point Charges, find the electric force exerted

    Homework Statement Three charges, each of magnitude 2 nC, are at separate corners of a square of edge length 1 cm. The two charges at opposite corners are positive, and the other charge is negative. Find the force exerted by these charges on a fourth charge q = +3 nC at the remaining (upper...
  10. deep838

    Why Does an Accelerated Charge Emit Photons and Lose Energy?

    My days in high school are almost at an end and I don't want to run to my teachers with this question. So can someone please explain this to me: why an accelerated charge emits photons and loses energy? Links and references are also welcome. Thanks in advance.
  11. Q

    Moving Charges and Magnetic Moments

    Does any moving charge generate a magnetic moment? I thought so because a moving charge generates a magnetic field.
  12. A

    Help electric charge Coulomb's law two charges?

    Homework Statement http://loncapa.vcu.edu/res/vcu/phys202/zzImages/two-charges-forces.bmp Problem#1: Two identical conducting balls, A and B, of identical masses m = 10 kg, are suspended in equilibrium by insulating massless strings in length L = 3 m. Both balls make the same angle θ = 30°...
  13. P

    Electrostatics and Coulumb's law, potentials and test charges

    I am given 4 potential charges, 1V, 3V, -6V, and 5V, all arranged randomly around each other. There is a test charge located at infinity. No distances are given between the potentials.1. Where will a test charge of 2*10^-6 C travel? 2. What is its kinetic energy? 3. Find the capatinance of a...
  14. M

    Electric Field at Surface of Earthed Sphere (using image charges)

    "A charged sphere is a distance d from the centre of an earthed sphere conducting sphere of radius a. An image charge (q') for this system is located at a distance b from the centre of the sphere where: q'= -(aq/d) and b=(a^2)/d Calculate the expression for the Electric field at point p...
  15. P

    How exactly do you find the net force between charges?

    I was doing some homework problems, and I came across a couple I didn't know. I then realized I must have screwed up my understanding on electrical forces. For an electrical force, if there are two protons, the force is k*q1*q2/r^2. The direction is in the opposite direction. <---(+)...
  16. S

    Electrostatic charges in ionic compounds

    From this link: http://www.chemguide.co.uk/atoms/structures/ionicstruct.html it explains why NaCl has a 6:6 coordinated structure and not an 8:8 coordinated structure. However, i don't really understand their explanation "Now imagine what would happen if you replaced the caesium ion with the...
  17. F

    Calculating Charges of Identical Tiny Conducting Spheres

    Homework Statement You have two identical tiny conducting spheres: sphere A carries positive charge qA, and sphere B carries negative charge qB. First the spheres are placed distance d = 0.404 m apart, and they attract each other with a force F1 = 0.748 N. Then the spheres are brought...
  18. R

    Electric field - Finding the charges

    Homework Statement Two point charges q1 and q2 are held 4.00cm apart. An electron released at a point that is equidistant from both charges, undergoes an initial acceleration of 8.05×1018m/s2 directly upward in the figure, parallel to the line connecting q1 and q2. Homework Equations...
  19. D

    Equation for speed of charges (electrostatics)?

    I am trying to do an exercise but there's no equation in the book that links speed and charges. Can anyone help? This is the exercise: Homework Statement There is a particle with mass = 20 grams and charge = 6 x 10^(-6) C, and another particle with mass = 50 grams and charge = -4 x 10^(-6) C...
  20. J

    Finding electric field between two charges

    Homework Statement Two charges, Q1 = 4*10-8 and Q2 = 2.7*10-8 are 3.25 m apart. What is the electric field magnitude halfway between them? Homework Equations E = kQ/r2 The Attempt at a Solution E1= k (4*10-8C)/(1.63m)2 = 135 N/C E2= k (2.7*10-8C)/(1.63m)2 = 91.4 N/C 135 N/C - 91.4 N/C = 43.5...
  21. Q

    Why does a magnetic field repel moving charges?

    Why does a magnetic field produce a force on a moving charge? I would love if someone answered why and not how.
  22. R

    Finding r using point charges and work done by an electric force

    Homework Statement A positive point charge (q = +8.9 10-8 C) is surrounded by an equipotential surface A, which has a radius of rA = 1.3 m. A positive test charge (q0 = +2.7 10-11 C) moves from surface A to another equipotential surface B, which has a radius rB. The work done by the electric...
  23. N

    Having trouble finding the potential between two positive point charges.

    Homework Statement How to find the potential between two positive point charges? I don't know where I'm going wrong. ==I am adding V_1 and V_2. converted mC to C, cm to m, correct value of k. V1= kq1 / r1 v2= kq2/ r2. ==I am adding both of these, but I'm not getting...
  24. P

    Net Force Exerted by Two Charges on a Third Charge (Coulomb's Law)

    This problem has been posted before with different values for each variable and I did as best I could to complete it similarly. However, when I attempt to input my final answer I get it wrong every time. I just wanted to see where I am going wrong, thanks. Homework Statement Coulomb's law...
  25. N

    Finding and labeling equilibrium points between multiple point charges.

    Homework Statement How to find equilibrium points between four point charges? How do you determine whether these equilibrium points are stable, unstable, or neutral? I know the sum of the forces should equal zero, but that's it. How do you determine the stability of the equilibrium...
  26. B

    Very hard Coulomb Force with two charges

    I'm new to forums and after I typed all this out and tried to submit, it cleared everything. I really need to get this problem finished tonight. Homework Statement You have two charges (q1 = -15uC and q2 = 3uC) separated by a distance (d = 3m). We want to calculate the electric field, E...
  27. D

    Calculate the amount of work required to assemble a system of charges.

    Homework Statement The three charges shown below (Q1=22.6*10^-6C, Q2=22.6*10^-6C, Q3=61.0*10^-6C) are at the corners of an iscoceles triangle with sides a=4 m and b=2 m. Q3 is 2m from Q1 and Q2, Q1 is 4m from Q2. In other words, Q3 is the point charge at the "tip" of the isosceles...
  28. P

    Two Point Charges: Physics Problem Help

    Greetings fellow physics adorers/ mathematicians, I was wondering if someone could help me with my posted problem. All the necessary details from the template are included in the screenshot on the right.
  29. B

    Three Charges in an Electric Field

    Homework Statement Three charges, q1 = 8.43nC, q2 = -4.29nC and q3 = 3.00nC are at the corners of an equilateral triangle, as shown in the figure below. A. The angle alpha is 60.0° and L = 0.448 m. We are interested in the point midway between the charges q1 and q2 on the x axis. For...
  30. A

    How Far is Charge Q1 from Point P Where the Electric Field is Zero?

    1.Two point charges, Q1 = -22 mμ C and Q2 = 51mμ C , are separated by a distance of 12 cm. The electric field at the point P is zero. How far is Q1 from P?...Sorry if my equations arent coming out right on the screen this is the first time I've posted on the forum, if you look at the thumbnail...
  31. A

    Are Identical Masses' Angles Equal for Different Charges?

    Homework Statement I have a problem as follows: "Two charges of identical mass hang from the same point by a thread of length l. One has charge q and the other has charge 2q. Find the angle each mass makes with the vertical." Now, I got an answer and found that each mass will make the...
  32. T

    Help with Point Charges and Charge by Contact

    1. Homework Statement Three small identical metal spheres carry electric charges, +Q, +2Q, and +3Q. The centres of the spheres lie in a straight line at fixed positions R, S and T, such that the distance between the spheres at R and S is d1 and that between the spheres at S and T is d2. Assume...
  33. W

    Two line charges lie in the XY plane

    Homework Statement Line A extends from (2,2, 0) to (-2, 2, 0) and line B extends from (2, -2, 0) to (-2, -2, 0). Each has a linear charge density ρl = 1 nC / m. You want to calculate the magnitude and direction of the electric field due to the two line charges for all points on the z-axis. a.)...
  34. F

    Proton-Proton Interaction at Minimum Separation

    I don't even know why I am having trouble with this problem. Homework Statement Two protons are initially an infinite distance apart. One of the protons is initially at rest, and the other is approaching the other at a certain speed. What kinetic energy must the other proton have so that their...
  35. R

    My brain has been shocked by this problem dealing with charges and Coulombs law

    My brain has been shocked by this problem dealing with charges and Coulombs law :( This is what I did... F = k*q1*q2/r^2 F = [ (8.99 * 10^9)(4.9 * 10-9)(6.0 * 10^-9) ] / (0.295)^2 F = 0.000000264 / 0.087025 F = 0.0000003034 F = 3.034 * 10^-7 N F = k*q1*q3/r^2 F = [ (8.99 *...
  36. M

    Distance from +4μC to Zero Potential: 24mm

    Homework Statement The diagram shows two charges, +4 μC and –16 μC, 120 mm apart. What is the distance from the +4 μC charge to the point between the two charges where the resultant electric potential is zero? A 24mm B 40mm C 80mm D 96mm Homework Equations potential equation...
  37. L

    Point Where Electric Field=0 (3 point charges on x-axis)

    Homework Statement Point charges of -7 µC, 1.0 µC, and +7 µC are located along the x-axis at x = -1.0 cm, x = 0, and x = +1.0 cm, respectively. Locate a point on the positive x-axis where the magnitude of the electric field is zero. Homework Equations E=(kQ)/r^2 E(total)=E(1)+E(2)+E(3)...
  38. T

    Parallel Plate Capacitor having equal charges on plates

    Homework Statement Q .1 The plates of a parallel plate capacitor are given equal positive charges. What will be the potential difference between the plates? What will be the charges on the facing surfaces and on the outer surfaces? Q.2 Each plate of a parallel plate capacitor has a...
  39. S

    Metal Surface Repels Electric Charges - Applications?

    I came across this piece of news, about how researchers have found a way to repel electric charges away from a surface: http://phys.org/news/2013-01-metal-surface-repel-electric.html I was thinking that perhaps it could be useful for more than just particle accelerator experiments. Could...
  40. F

    RC Circuit: Charges faster than discharges?

    Homework Statement This isn't a problem from a textbook, but it is homework. For a lab in class, we worked with simple RC circuits on breadboards. The strange thing I noticed is that the capacitor always charges faster than it discharges. I know that the Time constant should be T=RC, so I...
  41. M

    Distance between point charges in equilibrium (simple)

    Homework Statement Two fixed charges, +1.07 uC and -3.28 uC, are 61.8 cm apart. Where may a third charge be located so that no net force acts on it? Homework Equations Coulombs law The Attempt at a Solution q1 = 1.07 uC q2 = -3.28 uC q3 = q q1 ----- q2 ----- q q1 and q2...
  42. N

    Doubt regarding derivation of bound charges in dielectric

    In Griffiths, for deriving the bound charges for a given polarization P , the formula used is the general formula for dipoles .i.e ( equation 4.9) {Here the potential at r is calculated due to the dipole at r' ) V(r) = ∫\frac{x.P(r')}{X^2}d\tau' Here X = r - r' , and x = unit vector in...
  43. I

    Estimating the Ratio of theta1 & theta2: Two Spheres with Unequal Charges

    Two spheres S1 and S2 hang from light insulating strings of the same length from points P1 and P2 which are on the same level. S1 is of mass M and has charge Q. S2 is of mass M and has charge 2Q. Repulsion between S1 and S2 causes their strings to be inclined at angles of theta1 and theta2 to...
  44. P

    Finding the Force on One Point Charge Due to Multiple Point Charges

    Homework Statement Two +4 mC charges and two -4mC charges are arranged on a circle of diameter "d" as shown in the figure below. The magnitude and direction of the force on the +4mC charge at the top of the circle is: a) 6.39*10^6 N radially inward b) 1.2 * 10^7 N radially inward c) 2.4...
  45. P

    Finding the Force Between Two Point Charges

    Homework Statement Two point charges with charges of +5μC and -100μC are separated by 15 cm. The magnitude of the force between these charges is: a) 1.99 N b) 4.02 N c) 20 N d) 199 N e) 400 N Homework Equations F = q1q2 * k / r^2 The Attempt at a Solution F =...
  46. S

    Question about net electric field between two charges

    Homework Statement A charge +Q exists at a point and directly west of this point a charge -Q exists. What is the direction of the net electric field at the midway point? I'm studying old finals for my exam and this question keeps popping up in various forms. The answer is always directed...
  47. J

    Time it takes for two charges to collide

    Homework Statement Two charges with e+ and e- charge are separated a distance "a" apart. Assuming there's no gravity, how long does it take for the charges to collide? Homework Equations My professor said to use conservation. I'm guessing he means Wnc = (KE + PE) - (KEo + PEo) The...
  48. K

    How Do You Balance Forces in a Charged Rhombus?

    Hello, please help me solve this so I can learn from it. Image: http://i48.tinypic.com/30k8y10.jpg Two charges with charge +Q are placed at A and C vertices of a rhombus with four even sides (α). A prticle with mass m and charge -Q is placed at vertex B. An unknown charge size of q is...
  49. Saitama

    Is There an Easier Method to Solve Problems Involving Image Charges?

    Homework Statement (see attachment) Homework Equations The Attempt at a Solution I think i need to use method of image charges here but if i do that, i need to place infinite fictitious charges and finding the electric field at the surface of any of the plate would be very...
  50. avorobey

    Charges and energy transfer in a circuit

    I've been trying to understand what happens on a microscopic level - in terms of charges and EM fields - in a simple circuit (say a battery with wires to a lightbulb), and I'm finding it pretty difficult. I read these articles that try to untangle the flow of charge from the flow of energy, and...
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