What is Electric field strength: Definition and 135 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. R

    Electric Field Strength Between Two Charges

    Homework Statement Two isolated point charges, -7 μC and +2 μC, are at a fixed distance apart. At which point is it possible for the electric field strength to be zero? (A)......(B)...(C).....(D) o----------------------o----------o---------------o ......-7 μC...+2 μC...
  2. S

    Electric Field Strength Conservation in Direction of Motion

    (Sorry for the typo in the title. I don't know how to get rid of it) Recently I was looking at the Lorentz co-variance of F=dA (the Faraday 2-form) and *F=*dA (the Maxwell 2-form). I realized that Lorentz co-variance implies that the electric field strength and magnetic field strength are...
  3. U

    Electric field strength and electrostatic potential

    1. The problem is in the attachments. 2. Field strength is equal to voltage divided by distance 3. I want to make sure that i understand a few things before i solve this problem! i would like to know your opinion! a) first, field strength is inversely proportional to the the distance squared...
  4. E

    Do I have to re-define electric field strength in Centre of Mass frame

    So let's say I'm computing the torque as a result of the interaction between two electric dipoles in the lab frame. Let's imagine they are in some electric field. I then do : τ = r×F If I now switch to the centre of mass frame I have to find their position vectors from the COM. Why do...
  5. R

    Find the Electric field strength at a point between two charges

    Homework Statement See images Homework Equations See images The Attempt at a Solution I have tried parts C and D several times, and the homework program is telling me that it's still not correct. For C, I keep getting: 7.7x10^8 N/C for D I keep getting: 7.1x10^-12 N/C...
  6. C

    Calculating electric field strength, potential difference, and force.

    Homework Statement I'm pretty sure I have done questions 1 to 4 correctly, it is just question 5 I am struggling with. I have an exam in one week and this is revision so it will not get marked by a tutor, and it would really help if someone could give my answers a quick check and help me...
  7. J

    Find electric field strength between disks

    Homework Statement Two 2.0cm diameter disks face each other, 1.0mm apart. They are charged to -10nC and 10nC. -What is the field strength between the disks? -A proton is shot from the negative disk toward the positive disk. What launch speed must the proton have to just barely reach...
  8. snoopies622

    The uncertainty principle and electric field strength

    As my knowledge of an electric field strength becomes more precise, what physical quantity becomes correspondingly less precisely known?
  9. R

    Electric Field Strength at Center of Triangle

    Homework Statement Three positive charges, A, B and C, of 3 × 10-6, 2 × 10-6, and 3 × 10-6 Coulombs respectively, are located at the corners of an equilateral triangle of side 0.2 meters. Find the magnitude in Newtons/Coulomb of the electric field at the center of the triangle...
  10. A

    Electric field strength and potential in a charged conducting sphere

    The electric field strength inside a conducting charged sphere is zero, but why? In the book it says "that the field lines would link charges of opposite sign in the sphere and such a state of affairs is impossible under static conditions in a conductor." I don't really get this sentence. And...
  11. D

    Electric field strength between two points.

    Homework Statement Find the electric field strength at point P, which is located midway between charges A and B. The charges are separated by 20 cm. The first charge has a charge of 20 micro coulombs. The second charge has a charge of -30 micro coulombs. Homework Equations Electric...
  12. L

    Solving for Electric Field Strength & Direction of Charged Sphere

    Homework Statement What are the strength and direction of an electric field that will balance the weight of a 1.0g plastic sphere that has been charged t0 -3nC ? Homework Equations E= F/q The Attempt at a Solution Newton's laws on the charged sphere ƩFnet(y) = F -mg=0...
  13. T

    Electric field strength of van de graff generator

    A VDGG is used to produce a large PD. The dome of the generator has a radios of 0.15m. It is charged and gets a PD between the dome and the Earth of 75kV. The charged stored on it is : 5.0 x 10-6C Answer: Use of E = Q/4∏εr0. 3.0 x 105 My attempt: E = kQ/r2 = 8.99 x 109 x 5.0 x 10-6 /...
  14. F

    Electric Field Strength Inside Concentric Uniformly Charged Spheres

    Homework Statement The graph in the figure shows the electric field strength (not the field lines) as a function of distance from the center for a pair of concentric uniformly charged spheres. Which of the following situations could the graph plausibly represent? (There may be more than one...
  15. K

    Where Electric Field Strength + Potential are Zero?

    Homework Statement draw equipotential lines and electric field lines for the following arrangements of charges: a) +4 at (3,5) b) +4 at (3,5) and +4 at (6,5) c) +4 at (3,5) and -4 at (6,5) d) +5 at (3,5) and -2 at (6,5) e) +4 at (3,4), (7,4), and (7,7) f) +4 at (3,4) and (7,4) and -4 at...
  16. E

    Electric Field Strength and Potential

    Page 10 part (b) (ii) <click on the link Now, the question states : Use Fig. 4.2 to state and explain the distance x at which the rate of change of potential with distance is maximum Now electric field strength = negative potential gradient So in effect they're asking for the point at...
  17. K

    Electric field strength and electric potential in a sphere

    Given a solid metal sphere where all the positive charges are distributed evenly on the surface of the metal sphere. My textbook says that there is no electric field strength in the middle of the metal sphere because the charge = 0. However, my understanding is that wouldn't the center of the...
  18. G

    Electric field strength for a radial field.

    Homework Statement Q. A metal sphere of radius 20 cm carries a positive charge of 2.0 μC. a. What is the electric field strength at a distance of 25 cm from the centre of the sphere? b. An identical metal sphere carrying a negative charge of 1.0 μC is placed next to the first sphere. There...
  19. Darth Frodo

    Electric Field Strength problem.

    Homework Statement 2 point charges are situated 45nm apart in a vacuum. Charge A is +8μC and charge B is -25μC. X is a point 8nm from A. Calculate the electric field strength at point X only due to A (Ans is 1.2 x 10^9 N/C) Calculate the overall electric field strength at point X due to...
  20. P

    Electric Field Strength magnitude

    Hi, Four point charges of equal magnitude are held at the corners of a square. The length of each side of the square is 2a and the sign of the charges are the following: Two positive charges on the top two corners of the square and two negative charges on the bottom two corners of the square...
  21. I

    Calculating Electric Field Strength using Electric Potential?

    Homework Statement How do I calculate the Field Strength if I know the Potential? Homework Equations E = -\nablaV V = Electric Potential E = Electric Field Strength The Attempt at a Solution There's a problem in which I calculated the Potential, it's constant however. So according...
  22. matt_crouch

    Calculate the electric field strength inside and outside a wire

    Homework Statement An infinitly long conducting cylinder of Radius R carries a inform surface charge of (lambda per unit length) determine the electric field strength inside and outside the cylinder Homework Equations integral (E.ds)= q/e0 The Attempt at a Solution im not really sure what...
  23. M

    Electric Field Strength as a Vector along a line

    When Calculating Electric Field Strength using Q/kr^3, if the Q is negative is this negative disregarded? If not this would make E around a negative charge, negative. But if a positive test charge (q) is placed between two charges (Q1(negative) and Q2(positive)) then for Q1 (the negative charge)...
  24. T

    Calculating Electric Field Strength for a Point Charge and Proton Interaction

    Homework Statement (This was part of an assignment that we had to create, so the question is one of my own, although I'm not quite comfortable with this area, hence why I'm asking for help) Calculate electric field strength of a positive point charge of 1.3x10-7C that is 5.3x10-4m away from a...
  25. C

    Electric Field Strength Inside a Cylindrical Non-conductor

    Homework Statement Hey everyone, I'm just studying some physics, and came across this question where I don't know why I'm wrong =( It's from Physics (5th Ed.) by Halliday, Resnick and Krane - Chapter 27, Exercise 22 Positive charge is distributed uniformly throughout a long, nonconducting...
  26. D

    Current and electric field strength question

    Homework Statement A wire carries a current and consists of three sections with different radii. Rank the sections according to the following quantities, greatest first: (a) current, (b) magnitude of current density, and (c) magnitude of electric field. Homework Equations i =...
  27. M

    Projectile motion and electric field strength

    Homework Statement An electron is launched at a α=38.5° angle and speed of 4.12×10^6 m/s from the positive plate of the parallel plate capacitor shown. If the electron lands d=3.03 cm away, what is the electric field strength inside the capacitor? Homework Equations t = d/v v0y =...
  28. R

    Coaxial cable problem, electric field strength?

    Homework Statement A coaxial cable has an inner core diameter 6mm and inner diameter of the outer sheath is 20mm. There are two layers of insulation between the conductors, the inner layer from a radius of 3mm to 9mm has relative permittivity of 8 while the outer layer from radius 9mm to...
  29. H

    It is asking for the magnitude and direction of the electric field strength

    What are the magnitude and direction of the electric field strength at point Z in the following: Point X, q1 = -2.0 x 10^-5 and it is 60 cm to the left of point Y, q2 = 8.0 x 10^-6, which is 30 cm to the left of Z. Essentially, this is what it looks like: X-------Y--Z
  30. N

    Irradiance and electric field strength

    Dear physicists, I am desperate. I am using a QM code to propagate a wavefunction of a system that experienced an electric field pulse. However, in literature all values for the electric field strength are given in V/m but the program asks for W/cm^2! I am kind of very confused here and did not...
  31. J

    Measuring Tiny changes in Electric Field Strength

    Hi all I am looking to measure minute changes in electric field strength. I found this article http://www.physorg.com/news74876394.html" which describes how scientists at harvard isolated a single electron in a highly evacuated, absolute zero chilled chamber and manipulated its movement using...
  32. R

    Calculate electric field strength from voltage?

    Hi, I am trying to work out the electric field strength associated with a number of different electronic systems at a given distance. I am able to simplify the systems so that I only need worry about the fields from a high-voltage busbar or cable. I know that electric field strength from a...
  33. M

    Electric field strength at the midpoint between the two charges.

    Homework Statement A + 7.3 nC point charge and a - 2.4 nC point charge are 3.5 cm apart. What is the electric field strength at the midpoint between the two charges? Homework Equations E = 9*10^9(q/r^2) q = charge r = distance from point charge The Attempt at a Solution Since...
  34. Z

    Find the Electric Field strength

    Homework Statement "A copper cable carrying 50A current has radius 0.003m. What is the electric field if copper has a resistivity of 1.7x10^-8 Ohm/m?" Homework Equations Formula for current density etc. The Attempt at a Solution So I write: \vec{\mathbf{J}} = n|q|v_d = \frac{I}{A}...
  35. J

    Electric Field strength of sphere

    Hi everyone I just need some help with this question. Its a simple one I'm pretty sure. Homework Statement A solid sphere of radius 3 cm is made from a conductor and has a charge of + 4 uC placed upon it. What is the electric field strength 1 mm from the centre of the sphere? Homework...
  36. G

    Measuring Electric Field Strength

    I have to construct an experiment which measures the electric field strength at various distances from a charged Van Der Graaff generator. How would i go about this?
  37. D

    Calculating electric field strength

    Homework Statement http://img219.imageshack.us/img219/3310/problemi.png Homework Equations F = kq/r^2 The Attempt at a Solution O ----- x ----O -----------O Let the electric field of the first O be E1, second be E2, third be E3. RED - .02m BLUE - .016m GREEN - .033m E1...
  38. L

    Estimating electric field strength

    1. Estimate the electric field (strength and direction) at the point A. 5cmx5cm gridL 2. E = -dV/ds 3. I had four options, each a combination of 500 or 1000V/m for the E field strength and then left or right for the direction. I knew it must be to the left because the field...
  39. A

    Exploring the Relationship between Electric Field Strength & Potential Gradient

    Homework Statement What is the relationship between electric field strength and the potential gradient? Homework Equations The Attempt at a Solution This is my Calc based Physcis lab question but I am at a total loss. I do not understand what potential gradient is in the...
  40. JJBladester

    Limit Problem - Electric field strength of an infinite line of charge

    Limit Problem --- Electric field strength of an infinite line of charge Homework Statement What is the limit of the following equation? Homework Equations \stackrel{lim}{L\rightarrow\infty} \frac{K|Q|}{r\sqrt{r^{2}+(L/2)^{2}}} The Attempt at a Solution The book gives an answer...
  41. P

    Electric field strength of a wire comparison

    1. Homework Statement The electric field strength 7.79 cm from a very long charged wire is 2660 N/C. What is the electric field strength (in N/C) 12.7 cm from the wire? 2. Homework Equations E= (9*10^9) Q/ r^2 3. The Attempt at a Solution i have energy. so is tried to solve...
  42. K

    Calculating Electric Field Strength from a Charged Wire

    Homework Statement The electric field strength 8.05 cm from a very long charged wire is 1310 N/C. What is the electric field strength (in N/C) 30.0 cm from the wire? Homework Equations E=F/Q E=KQ/R^2 The Attempt at a Solution First I try to find the charge using E=KQ/R^2...
  43. G

    Parallel Plate Capacitor: Electric field strength, flux & magnetic field

    Homework Statement This is a question on a past paper of a second-year undergraduate physics paper. A parallel plate capacitor is charged and the voltage increases at a rate of dV/dt. The plate radius is R and the distance between the plates is d. (a) What is the electric field...
  44. R

    Is Object A Positive and Object B Negative Based on Electric Field Direction?

    It is not a homework problem, thought it can kinda be. But when they show you a diagram with object A and B, If the electric field point towards A and away from B. Does that mean that A is + and B is -?
  45. M

    Calculating the voltage and electric field strength between two parallel plates

    Homework Statement - How much is the electrical voltage U between two evenly electrified parallel flat plates, distanced d = 1 cm, if the strength of electric field between them is E = 1 V / m? - - What is the strength of electric field to the left and to the right of each plate? - What is...
  46. R

    Calculating Electric Field Strength of Three Point Charges - Convert to V/m

    Hey i worked out this answer for the electric field strength at a point due to three point charges. E = -46736i + 46736j -39546k How do i convert this to V/m? eg. 12345 V/m I have checked everywhere Thanks for any help
  47. H

    Electric field strength before reaching the state of electrostatic equilibrium

    Homework Statement In such a picture, http://i1021.photobucket.com/albums/af335/hectoryx/electrostaticequilibrium_1.jpg Induced charges will emergence on the left and right side of non-perfect conductor B, because the effect of the electric field of conductor A. As is known to all, when...
  48. C

    Electric Field Strength- variations

    If the electric field lines are curved as opposed to straight, say from straight parallel lines parabolic curves develop, would there be any change in the field strength? ie would it be stronger when the lines are parallel than when they curve?
  49. S

    Question about Electric Field Strength and Electric Potential

    Lets say I have a point charge X placed on a region between a +Q test charge and +2Q point charge where electric field strength is zero. Since E=-dV/dR, does it mean V=0 or constant? Can the point charge move if i place it there? Well let's just ignore gravitational field/force here.
  50. D

    Potential difference to find the magnitude of the electric field strength

    what are the components to find the magnitude of the electric field strength when only potential difference and that there are two oppositely charged plates that are separated by a given distance.
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