What is Electric forces: Definition and 69 Discussions

An electric field (sometimes E-field) is the physical field that surrounds electrically-charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field for a system of charged particles. Electric fields originate from electric charges, or from time-varying magnetic fields. Electric fields and magnetic fields are both manifestations of the electromagnetic force, one of the four fundamental forces (or interactions) of nature.
Electric fields are important in many areas of physics, and are exploited practically in electrical technology. In atomic physics and chemistry, for instance, the electric field is the attractive force holding the atomic nucleus and electrons together in atoms. It is also the force responsible for chemical bonding between atoms that result in molecules.
Other applications of electric fields include motion detection via electric field proximity sensing and an increasing number of diagnostic and therapeutic medical uses.
The electric field is defined mathematically as a vector field that associates to each point in space the (electrostatic or Coulomb) force per unit of charge exerted on an infinitesimal positive test charge at rest at that point. The derived SI units for the electric field are volts per meter (V/m), exactly equivalent to newtons per coulomb (N/C).

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  1. M

    The vector sum of the electric forces exerted on a particle

    r_{13}=r_{23}=\sqrt{(30*10^{-3})^2+(90*10^{-3})^2}=\sqrt{9*10^{-3}}\\ F^E_{13}=F^E_{23}=9E9\cdot\frac{5*10^{-9}\cdot3*10^{-9}}{9*10^{-3}}=1.5*10^{-5}\\ \theta=tan^{-1}(\frac{90*10^{-3}}{30*10^{-3}})=71.565\,degrees\\ \vec{F}^E_{13}=<F^E_{13}cos\theta, F^E_{13}sin\theta> = <4.743*10^{-6}...
  2. jisbon

    Electric forces between conducting rod and rail

    Alright, to start off: I'm not even sure how this works in the first place. What I do understand is that if they carry current in the opposite direction, using right-hand grip rule, the magnetic field between them will be the same (into the page). Hence using the left-hand rule, I can deduce...
  3. I

    Electric Fields and Electric forces help

    Homework Statement This is the question Structure opposite comprises 5 ions each of which has lost one electron. The sides of the square formed by the 4 outer ions are of length 0.2nm Ion E is at the midpoint 1.What is the force on A due to ion A?Homework Equations I'd imagine: F= kq / r^2...
  4. A

    How does the transfer of electric forces between two objects work

    Questions 1.) Here, the negative charge from the wool is transferred to the plastic rod. I'm curious as to what determines which object is responsible of transferring their charge to the other object. Like why didn't the plastic rod give its negative charge instead? 2.) If we rub 19 more...
  5. jlmccart03

    Electric Forces and net electric force?

    Homework Statement Problem # 4:[/B] A thin semicircular rod has a total charge +Q uniformly distributed along it. A negative point charge -Q is placed as shown. A test charge +q is placed at point C. (Point C is equidistant from -Q and from all points on the rod.) http://imgur.com/AeVfddb Let...
  6. S

    How to find the mass of a pith ball using electric forces?

    Homework Statement A pith ball is charged by contact with a Van De Graaff machine, and is repelled away from the dome. It remains at its location. Using the chart given, what is the mass of the pith ball? Distance between centre of generator and pith ball...
  7. Phy_TR

    Help with Electric Forces Problem and Equilateral Triangles

    Homework Statement The point charges in the figure have the following values: q1=+2.1μC, q2=+6.3μC, q3=−0.89μC. Suppose that the magnitude of the net electrostatic force exerted on the point charge q2 in the figure is 0.57 N . Find the distance d and the direction (angle) of the net force...
  8. H

    How Does Charge Affect Motion in Outer Space?

    Homework Statement In outer space, a ball with mass 0.25kg and charge +4/K C is shot from 5m towards a +0.5C charged ball with an initial velocity of 20 m/s What main Physics principle should be used to solve this problem? What is the closest the small ball will get to the large one? What is...
  9. Toon

    Electric Forces with particles and Columbs law problem.

    Homework Statement Two particles, one with charge -7.13 × 10-6 C and one with charge 1.87 × 10-6 C, are 0.0284 meters apart. What is the magnitude of the force that one particle exerts on the other? Two new particles, which have identical positive charge q3, are placed the same 0.0284 meters...
  10. A

    Electric Fields: Oscillating point charge

    Homework Statement Reading a journal from that crazy old retired physics professor on the hill, you stumble upon a scheme to generate high frequency (HF) radio waves (λ = 10 m). It requires generating an electric field that diverges from a point and increases in strength linearly with respect...
  11. W

    Electric potential, Can Someone Check This?

    Homework Statement A particle charge of 7.6μC is in a uniform electric field directred to the left. Another force, in addition to the electric force, acts on the particle so that when it is released from rest it moves to the right. After it has moved 8cm, the additional force has done...
  12. M

    Electron traveling between two plates. Electric Fields?

    Homework Statement An electron traveling horizontally east passes between two horizontal, oppositely charged plates and is deflected downward. Part A: Passing through the same space between the plates, in what direction (if any) a proton traveling horizontally east would be deflected? Part B...
  13. Rugile

    Electron's movement due to electric forces

    Homework Statement 4 electrons are moving due to electric forces. Find their velocity when they are very far away from each other, if initially they were on a square's (side length a = 20 cm) vertexes. Homework Equations F = \frac{kq_1q_2}{r^2} k = \frac{1}{4\pi\epsilon_0} The...
  14. NATURE.M

    Electric Forces, Balloon Problem

    Homework Statement Two balloons A and B are filled with He gas. They have identical radii of 10 cm. The balloons are made with rubber so that they can be charged by rubbing against hair. They are held together with insulating strings, whose mass and charge can be ignored for this problem...
  15. dwn

    Electric Forces Homework: Calculate Two Point Charges Using Coulomb's Law

    Homework Statement Two point charges are 3 m apart and their combined charge is 20µC. If they repel each other with a fore of 0.075 N, what are the two charges? Ans: 15 μC and 5μC   Homework Equations F=k(q1*q2)/r^2 (could someone mention in their response how we use the math...
  16. C

    Net electric forces on a point charge

    Homework Statement In the figure, what is the force on charge Q3? Q1 = 5×10-6C, Q2 = -3×10-6C, Q3 = 4×10-6C http://www.usi.edu/science/physics/pickett/206/4p2f1.jpg Homework Equations Coulomb's law The Attempt at a Solution I thought I could just find the charges on q1 and 3 and...
  17. K

    How Is Electric Force Calculated Without Distance?

    Homework Statement Find the magnitude and direction at the midpoint of two point charges q1=20nC and q2=-40nC Homework Equations How can we answer the question if we aren't given the distance? The Attempt at a Solution Do I solve in terms of x for distance and use the formula...
  18. C

    Electric Forces in a Triangle (math check?)

    Hi Guys I've tried to do this problem but the answers are not being accepted is the math wrong? or did i forget a concept? Thanks for taking a look The triangle is set by Q1 on the top of the triangle Q2 on the bottom left and Q3 on the bottom right Calculate the magnitude of the net...
  19. C

    Electric Forces and Coulomb's Law Problem

    Homework Statement In the figure, the net electrostatic force on charge Q2 is zero. If Q1 = -5 nC and Q2 = +7 nC, determine the magnitude of Q0. http://www.webassign.net/bauerphys1/21-p-079-alt.gif Homework Equations F = (k*q1*q2)/d^2 The Attempt at a Solution I notice that Fnetx...
  20. F

    Electric Forces and fields question

    Two charges are placed at an equal distance x from point P, as shown in the following diagram. Charge A is placed directly west of P and B is placed directly north of P. 1)If A is given a charge of –Q and B is given a charge of +Q, what is the direction of the resulting electric field at...
  21. M

    Electric forces and Electric fields question on x and y components

    Homework Statement please see the pictures! Homework Equations F=k(q1)(q2)/r^2 The Attempt at a Solution okay, I am just curious as to why t cos theta and mg are x components when they are clearly on the y axix! I thought you used cos for x components and sin for y components
  22. D

    Calculating Electric Force on an Electron Near a Point Charge

    Homework Statement You are observing the effects of single point charge with a magnitude of +4.3muC. If a singe electron is placed 10cm to the right of this charge, what is the magnitude and direction of the electric force it will experience?Homework Equations E= Fe/q E= kq/r^2 The Attempt at...
  23. W

    Electric Forces and Fields questions,

    Electric Forces and Fields questions, please help! 1. Charge A and Charge B are 2.2 m apart. Charge A is 1.0 Coulomb, Charge B is 2.0 Coulombs, and Charge C is 2.0 Coulombs and is located between Charges A and B and is in electrostatic equilibrium. How far from Charge A is Charge C? 2. Two...
  24. T

    How Are Electric Forces Related to Electromagnetic Waves?

    Ive heard it said that electricity and megnetism are brought about by electromagnetic waves, but arent electric forces the cause of the other 2?
  25. T

    Electric Forces between three charges

    An electron is near a positive ion of charge +9e and a negative ion of charge −8e (see the figure below). (Take a = 5.23 µm, b = 4.28 µm, and θ = 54.9°.) (a) Find the magnitude and direction of the resultant force on the electron. (Let right be the +x-direction. Measure the angle...
  26. T

    Electric Forces between charges

    [b]1. Hanging from threads are two charged balls made of pith (a very light, spongy material that comes from inside the stems of certain plants). The balls each have a mass of 0.100 g and a charge of the same magnitude q and are attracted toward each other, as shown in the figure below...
  27. J

    Superposition of electric forces question

    Homework Statement Four point charges of +/-Q are arranged on the corners of a square of side L. What is the net electric force that these charges exert on a point charge q placed on the center of the square (formula in terms of Q, q, L and Coulumb constant k)?Homework Equations F=kQq/r^2The...
  28. P

    Why field lines are tangent to direction of electric forces

    can anybody tell me why electric field of lines are tangent to direction of electric force please be fast need it urgently...
  29. K

    Electric Forces on Point Charge q in Triangle ABC

    Homework Statement Point charges Q, -2Q and 3Q are situated at the corners A, B and C respectively of an eqilateral triangle of side l, and another point charge q, of the same sign as Q, is placed at the centre of this triangle. What is the force acting on the charge q, and what is the angle...
  30. H

    Electric Charges, Electric Forces and Electric Fields

    Homework Statement An object with a net charge of 24 x 10^-6 Coulombs is placed in a uniform electric field of 610 N/C, directed vertically. What is the mass of this object if it floats in this electric field? Homework Equations Felectric = kC (q*q/r^2) Electric Field= kC (q/r^2) E=...
  31. M

    How Many Electrons Are Removed from a Charged Copper Ball?

    Homework Statement A 3.0mm-diameter copper ball is charged to 50nC.What fraction of its electrons have been removed? The density of copper is 8900kgm^3. Homework Equations d=m/v; v=4/3* pi r^3 The Attempt at a Solution I worked through it and got 5.682 E -16, but that answer was...
  32. A

    Electric Forces: Find Separation Force

    Homework Statement So, we have two opposite and equal charges with a distance r between them, and we want to find the "separation force". Homework Equations Coulomb's Law The Attempt at a Solution Is the separation force the sum of the electric forces on both particles? Or is it...
  33. D

    Electric Forces: Coulomb’s Law Help

    Homework Statement Two identical small spheres of mass 2.0 g are fastened to the ends of an insulating thread of length 0.60 m. The spheres are suspended by a hook in the ceiling from the centre of the thread. The spheres are given identical electric charges and hang in static...
  34. S

    Conservative Nature of Electric forces

    My textbook says for every electric field due to a static charge distribution, the force exerted by that field is conservative. If that force is used to accelerate a charged particle, wouldn't the particle disapate some of its energy, as EMR? therefore you cannot say U_a + K_a = U_b + K_b as...
  35. J

    Electric forces, net force = zero

    Homework Statement Three charges lie along the x -axis. The positive charge q1 = 10.0 microC is at x = 1.00 m, and the negative charge q2 = -2.00 microC is at the origin. Where must a positive charge q3 be placed on the x-axis so that the resultant force on it is zero? Answer: x = - 0.809 m...
  36. A

    Need help solving electric forces and fields

    These are the problems I have left to do, but I have no clue as to how to solve them. Homework Statement a. Two small metal spheres are 23.0 cm apart. The spheres have equal amounts of negative charge and repel each other with a force of 0.040 N. What is the charge on each sphere? b.A tiny...
  37. G

    Electric Forces Lab Homework: Calculating Charge of Pith Balls

    Homework Statement When the pith balls are suspended, all forces are balanced. Assuming a mass of 0.060g for each pith ball, calculate the electric force which is repelling the pith balls. Hint: draw a free body diagram and apply Newton's 2nd Law seperately in the x and y directions...
  38. P

    Massive objects and electric forces

    I can understand why the gravitational force is weak for subatomic particles like the electron and the proton , since they have extremely minuscule masses. I don't understand why the electric force is soo weak for massive bodies, like humans and planets. Why isn't the Earth able to levitate...
  39. P

    Finding Equilibrium Charge: Solving for the Number of Electrons Transferred

    Please Help! Weve just started Physics II and I am lost already. We have been studying Electric forces and fields and now my homework is due tonight by 11pm and I can't even answerer the first question. I thought this would be an easy chapter since there weren't many formulas but I am...
  40. K

    Electric Forces and Field HELP

    Homework Statement While studying for ap physicsb, i came across this question and I'm so confused! There's a sphere with CHarge C in the center of the sphere, and Point P on the surface of the sphere. There are three separate charges +q on the surrounding area.. The question is what...
  41. O

    Electric field and electric forces

    Homework Statement An electron is projected with an initial speed v0 = 2.00×10^6 m/s into the uniform field between the parallel plates, as shown in figure. Assume that the field between the plates is uniform and directed vertically downward, and that the field outside the plates is zero. The...
  42. K

    Electric Forces: Calculating Charge on Two Spheres

    [B]Homework Statement Two small metallic spheres, each of mass 0.14 g are suspended as pendulums by light strings from a common point as shown. The spheres are given the same electric charge, and it is found that the two come to equilibrium when each string is at an angle of 7◦ with the...
  43. W

    Calculating Electron Count and Net Charge in Water

    First post here, so I wanted to say hello first of all. Must admit this board seems quite helpful. Anyways, here's my problem I'm having issues with, any help would be great. Water has a mass per mole of 18.0 g/mol, and each water molecule (H2O) has 10 electrons. (a) How many electrons are...
  44. B

    Finding Electric Forces Between Identical Spheres

    Homework Statement Two identical conducting small spheres are placed with their centers 0.300m apart. One is given a charge of 12.0 nC and the other a charge of -18.0 nC. a) Find the electric force exerted by one sphere on the other. b) Next, the spheres are connected by a conducting wire...
  45. D

    Vector Addition of Electric Forces in a Plane

    The problem I'm trying to solve involves the effect that two charges has on a third and I need to find the magnitude of the resulting force. In this particular problem it's the effect of A and B on C. The work I've done so far is attached so please take a look. I've been trying to add...
  46. B

    More electric forces pleaseee help

    Homework Statement Charge q2 experiences no net electric force. What is q1? (s=8.71 cm, q=-1 nC.) Homework Equations F = K * Q * Q1 / r^2 The Attempt at a Solution How I solve for Q1 if I don't know F?
  47. B

    Electric Forces: Need Help Solving!

    Electric Forces...need help! Homework Statement Two small plastic spheres each have a mass of 2.85 g and a charge of -39 nC. They are placed 3.06 cm apart (center to center). A. What is the magnitude of the electric force on each sphere? B. By what factor is the electric force on a...
  48. S

    Electric Force Homework: Calculate Charge on Spheres

    Homework Statement Two identical small spheres of mass 2.0 g are fastened to the ends of an insulating thread of length 0.60m. The spheres are suspended by a hook in the ceiling from the centre of the thread. The spheres are given identical electric charges and hang in static equilibrium, with...
  49. S

    Problem from Electric Forces: Coulomb's Law section

    Hello, I'm having problems with the following question: Neutral metal sphere A, of mass 0.10 kg, hangs from an insulating wire 2.0 m long. An identical metal sphere B, with charge -q, is brought into contact with sphere A. The spheres repel and settle as shown. Calculate the initial Charge on...
  50. B

    Electric Forces: Solve for Distance Below

    Homework Statement An electron is released a short distance above the surface of the Earth. A second electron directly below it exerts an electrostatic force on the first electron just great enough to cancel the gravitational force on it. How far below the first electron is the second...