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. G

    B Electric Flux - confused about integrating over a tilted area

    I have been thinking today about electric flux and it got me (as always) into confusion. I love to dig deeper and sometimes, I deviate from the truth. Let's consider the tilted surface where Electric field is passing by. I'm attaching the image as well. I know that to calculate flux, we must do...
  2. V

    Why is electric field at the center of a charged disk not zero?

    The electric field strength at the center of a uniformly charged disk should be zero according to symmetry of concentric rings about the center, where each ring is contributing to the electric field at the center of the disk. For a thin ring of uniform charge distribution the formula is ##E =...
  3. Tesla In Person

    Electric field strength at a point due to 3 charges

    I got E. 13q as the answer. That is what i did: The electric field due to +q at origin 0 should equal the electric fields of charges -3q and the new charge placed at 2x. So applying the equation above like this; k*(q) / (2^2) = -3q*k + (k*C)/ 4 solving for C the new charge added, gives 13q. I...
  4. S

    Calculate the charge on an oil droplet

    The book gives an answer of Q = 3.2 x 10^-19C I get an answer of 6.67 x 10^-19C. Workings below:
  5. radiant_june

    Electric field strength at a point between charges

    Find the electric field strength at point B between two charges shown below: Given/Known Values q1 = 4.0×10-6 C r1 = 40 cm = 0.4 m (Distance from q1 to point B) q2 = -1.0×10-6 C r2 = 30 cm = 0.3 m (Distance from q2 to point B) k = 9.0×109 Nm2/C2 Equations Electric Force: FE = (k⋅q1⋅q2)/r2...
  6. starstruck_

    Calculating electric field strength

    Homework Statement A cylinder of radius R= cm 1.2 and length L= 51 cm has a charge Q=2.3 μC spread uniformly along its surface (and not on its flat ends). a) Calculate the electric field strength a distance d=4 mm from the cylinder’s surface (not near either end) b)Calculate the electric...
  7. B

    Electric field in a capacitor with multiple dielectrics

    Hi, I am trying to understand capacitors and have come across the example in the attached image. What I would like to understand is how to calculate the electric field at some distance x within the capacitor. With x>>R , x<R and x=R . The image is of two circular disks as the...
  8. C

    Electric field strength between charged plates help

    Homework Statement Homework EquationsThe Attempt at a Solution E=kq/d2 how do I involve the kinetic energy K in the equation?
  9. C

    Electric field strength between charged plates

    Homework Statement Homework EquationsThe Attempt at a Solution E=kq/r2 so when the distance increase E should decrease? I know this is wrong, but can someone explain why? Thanks
  10. C

    Which point has the strongest electric field strength in this scenario?

    Homework Statement Homework EquationsThe Attempt at a Solution I tried to use the formula: F=kq1q2/r2 So at point B, the electric field strength is( 2kQ/r2) - (-kQ/r2)= 3kQ/r2 At A: (2kQ/r2)+(-kQ/r2)=kQ/r2 At C: -(2kQ/r2)-(-kQ/r2)=-kQ/r2 So B is the strongest? Is there an easier way to do it?
  11. chopnhack

    Electric field strength on particles of various distances

    There is no math in this one! I just wanted to know if I had the idea correct. Homework Statement If I have two positively charged particles at a distance between them that a field is produced between and around them, will test particles that repel away be solely a function of their distance...
  12. psy

    Calculation of the electric field strength

    Hey, First I want to find the electric field strength from the middle between two point charges q1 = 8nC and q2 = -6nC. The distance between the two charges is 10 cm. Then i want to find out at which point of a straight line, which runs through the two charges is the electric field strength...
  13. F

    Electric field strength inside a conductor

    I read on physics.stackexchange that using Gauss Law we can prove that the electric field strength increases as the radius increases inside a metallic conductor. Later on the same website, I encountered a contradicting statement that claimed that inside a conductor, the charges aren't free to...
  14. P

    Electric field strength in an ink-jet printer

    Homework Statement One type of ink-jet printer, called an electrostatic ink-jet printer, forms the letters by using deflecting electrodes to steer charged ink drops up and down vertically as the ink jet sweeps horizontally across the page. The ink jet forms 29.0 μm diameter drops of ink...
  15. M

    Difference Electric Field Strength Point Charges vs. Plates

    Why does the electric field strength on a straight line (E = k.(Q1/d12+Q2/d22). D1,2 = distance with respect to Q1,Q2) between two point charges vary with the location on this line while the field strength between two parallel plates which remains the same anywhere between the plates...
  16. Iron_Man_123

    Electric field strength -- calculating distance from charge

    Homework Statement At a distance D from a very long (essentially infinite) uniform line of charge, the electric field strength is 1000 N/C. At what distance from the line will the field strength to be 4000 N/C? Homework Equations E=kq/r2 The Attempt at a Solution I know that E is inversely...
  17. jlmccart03

    Find electric field strength expression for a specfic region

    Homework Statement A thick, spherical shell of inner radius a and outer radius b carries a uniform volume charge density ρ. Find an expression for the electric field strength in the region a<r<b. Homework Equations Gauss's Law ∫E⋅dA Area of a sphere The Attempt at a Solution I know I am...
  18. jlmccart03

    Electric field strength near a metal plate

    Homework Statement A total charge of 21 μC is applied to a thin, 1μm square metal plate 72 cm on a side. Find the electric field strength near the plate's surface, far from the edges. Homework Equations I think E = kq/r^2, but I really don't know. The Attempt at a Solution I am...
  19. Matticus9

    Calculating Electric Field Strength of a Charged Metal Sphere

    Homework Statement A metal sphere with a diameter of 10 cm has a charge distribution of 1.09085 x 1018 electrons/cm2 on its surface. What is the electric field strength at a distance of 25 cm from the surface of the sphere? (Answer: 5.5 x 1012 N/C) Homework Equations I wasn't given any...
  20. S

    Electric field strength with distance

    Consider Gauss's law in ##1## space and ##1## time dimension. In this case, ##\int\ \vec{E}\cdot{d\vec{A}}=\displaystyle{\frac{Q}{\epsilon_{0}}} \implies 2 E =\displaystyle{\frac{Q}{\epsilon_{0}}} \implies E =\displaystyle{\frac{Q}{2\epsilon_{0}}}##, where the factor of ##2## comes from the...
  21. C

    Electric field strength at a point between charges

    Homework Statement A +1.0 μC charge is placed at point X. A +4.0 μC charge is placed at point Y, 50 cm from X. How far from X, on the line XY, is the point where the electric field strength is zero? Homework Equations E = Q/4πε0r2 The Attempt at a Solution I know that the electric field is...
  22. J

    Electric field strength in metal sphere

    1. Homework Statement Why is there no electric field strength in a metal sphere? Is it because the sum of the individial electric field strength of the charges in the sphere is zero? How is that possible? Homework EquationsThe Attempt at a Solution
  23. K

    Is this how to attempt this problem on electric field strength

    Homework Statement Two parallel plates at -50kV and 100kV have separation 35cm. a proton is placed between the plates. calculate the electric field strength between the plates Homework Equations E=v/d The Attempt at a Solution 100kV--50kV=150kV 150x10^3/0.35=428571.4N/C
  24. Physics Dad

    Electric Field Strength - Assignment Question

    Homework Statement The Nucleus of a helium ion contains two protons approximately 5x10-15m apart. They can be considered to be surrounded by one orbiting electron approximately 5x10-11m away. Calculate the following: a) The electrostatic force between the two protons b) The electrostatic...
  25. henrco

    Find the rms electric field strength of a given EM wave

    Hi, I was able to correctly calculate the answer to part 1 below but the answer to part 2 is incorrect and I cannot see the error of my ways... any help gratefully received. 1. Homework Statement An electromagnetic wave has an intensity of 127 W/m2. 1) Find its rms electric field strength...
  26. K

    Uniform electric field - tension & electric field strength

    Homework Statement A ball with a mass of 3.0 x 10-4 kg hangs from a 15 cm long thread between two parallel plates. The thread is deflected to the side, as shown in the following diagram. The charge on the ball is +5.0 x 10-5 C. a) Find the tension in the thread b) Find the magnitude and...
  27. Y

    What is the electric field strength inside the capacitor?

    Homework Statement [/B] An electron is launched at a 45∘ angle and a speed of 5.0×10^6 m/s from the positive plate of the parallel-plate capacitor shown in the figure (Figure 1) . The electron lands 4.0 cm away. a) What is the electric field strength inside the capacitor? b) What is the...
  28. 1

    Electric Field Strength Question

    I already posted this, but it was on the wrong section. This is from the 2009 HSC exam. (I'm in Australia) I checked the answers and found that electric field strength was E = 100/0.10 = 1000V/m My question is, what would the electric field strength be if the positively charged plate was...
  29. P

    Electric field strength from x=-a to x = a

    Homework Statement I attached a file. Numbers 10 and 12. Homework Equations kQq/r, kQq/r^2 The Attempt at a Solution I am confused about this problem. Shouldn't the electric field strength be 0 when x = 0? The charges are opposite and adding two opposite vectors with equal magnitude should...
  30. SquidgyGuff

    Distance independence of electric field strength

    I was just wondering why the strength of the electric fields of insulating surface charges like sheets and shells aren't dependent on the distance from the charge according to Gauss's Law?
  31. Corey Bacon

    Electric field strength between two disks?

    Homework Statement Two 3.0 cm diameter disks face each other, 1.9mm apart. They are charged to $$\pm 16nC$$. (a). What is the field strength between the disks? (b). A proton is shot from the negative disk toward the positive disk, what launch speed must the proton have to barely reach the...
  32. K

    Can Electric Field Strength describe the Electric Field?

    We have two difference electric fields A and B. We are standing at point W1 in field A and the potential at a point M1 which is 0.5 meter left is 10 volts while the potential at point M2, which is 0.5 meter right, is 5volts. The potential difference between M1 and M2 is 5volts and the strength...
  33. B

    Solving for Electric Field Strength

    Homework Statement An electric dipole is formed from 1.0 nC charges spaced 2.4 mm apart. The dipole is at the origin, oriented along they-axis. What is the electric field strength at the following points? a. (x, y) = (10 cm, 0 cm) b. (x, y) = (0 cm, 10 cm)Homework Equations Pythagorean Theorem...
  34. S

    Net Electric Field Strength at a Point due to a Uniform Electric Field

    Homework Statement A uniform electric field exists everywhere in the x, y plane. This electric field has a magnitude of 3600 N/C and is directed in the positive x direction. A point charge -9.8 × 10-9 C is placed at the origin. Find the magnitude of the net electric field at y = +0.20...
  35. J

    Homework, electric field strength at centre of a square

    Homework Statement 4 charges of +5µC, +3µC, -4µC and +2µC form the 4 points of a square of side length 2m. Calculate the field strength and potential at the centre of the square. Homework Equations F=1/4πhttp://upload.wikimedia.org/math/d/3/c/d3c305fc416b971cd6d284564e51bf85.png0 X Q1Q2/r2 E=...
  36. S

    Surface Area and electric field strength

    This is my first post but I have frequented the forum for a little while now. I tried to figure things out myself and often times I am lead here by google. So my question is this: How is the electric field of an object altered when the surface area of the object is altered? Example: Take a...
  37. P

    Electric field strength from two charges

    Homework Statement Two identical point charges, q1 = +2.5 x 10-6 C and q2 = +2.5 x 10-6 C, are placed as shown in the diagram below. Point P is a distance 0.05 m from q1 and 0.12 m from q2, such that the angle at P is 90 degrees. Calculate the magnitude of the Electric field E at point P...
  38. N

    How does a dielectric increase maximum electric field strength?

    Homework Statement How does a dielectric increase maximum electric field strength? From the two cases where a dielectric is inserted into a charged capacitor after it is disconnected and after it is remained connected it seems that E will either decrease or stay the same. But I read in...
  39. A

    Electric field strength at the center of an equilateral triangle

    Homework Statement 3 rods each of length 1 meter form an equilateral triangle. Two rods have a uniform charge distribution of 8\times 10^{-6} C and the third of -8\times 10^{-6} C. What is the electric field strength at the center of an equilateral triangle Homework Equations \vec{E} =...
  40. R

    Concerning differentials in electric field strength calculations

    Hi guys, first time posting here, but I have a question that I have been thinking about for quite a while, and I hope someone can help out with it. Assume a line of charge (with overall charge of +Q and of length L) that is lying on the x-axis. You want to calculate the electric field strength...
  41. B

    What is the net electric field at point P in this physics problem?

    Physics Problem , please help I'm writing a test tomorrow and want to know if I'm right. The Question : Two point charges Q1 and Q2 are spaced 3m apart. Q1's charge = 14C Q2's charge = +20 C *Q1 -------(3meters)------- *Q2 ----(2meters)---- *P Calculate the net electric field at...
  42. Q

    Electric field strength goes to 0

    Homework Statement Two point charges lie on the x-axis. Charge Q1= +7 μC is located at x = 0 and charge Q2 = -18μC is located at x = 25 cm. Find the point on the x-axis (in cm) where the net electric field is zero. Homework Equations E = F/C F = k(q1)(q2)/r^2 The Attempt at a Solution Okay...
  43. L

    Simple electric field strength problem

    Homework Statement How far away from a 360μC charged particle is the electric field strength 49mN/C? Homework Equations E=(8.99x10^{9} x \frac{Q}{r^{2}} The Attempt at a Solution I assumed it would be a simple case of rearranging the equation to give r=\sqrt{\frac{8.99x10^{9}xQ}{E}}...
  44. N

    Electric field strength at the center of semicircle

    Homework Statement A uniformly charged insulating rod of length 12.0 cm is bent into the shape of a semicircle as shown in the figure below. The rod has a total charge of −7.50 µC. Find the magnitude of the electric field at O, the centre of the semicircle. Homework Equations E = 2kq /...
  45. N

    Electric Field strength between 3 charges and directions

    Homework Statement Three point charges lie along a straight line as shown in the figure below, where q1 = 6.36 µC, q2 = 1.57 µC and q3 = −1.82 µC. The separation distances are d1 = 3.00 cm and d2 = 2.00 cm. Calculate the magnitude and direction of the net electric force on each of the...
  46. N

    Electric field strength of 4 charges positioned in a square shape

    Homework Statement Four charged particles are at the corners of a square of side a as shown in the figure below. (Let A = 3, B = 5 and C = 6.) (a) Determine the electric field at the location of charge q. (Use the following as necessary: q, a, and ke.) (b) Determine the total...
  47. L

    Electric Field Strength Between Two Parallel Plates Problem

    Homework Statement If the electric field strength between two parallel plates 1cm apart is 3.1kN/C, how much energy will be used by the electric field to move an electron (placed half way between the plates) 3mm nearer to the positively charged plate? Homework Equations Work Done =...
  48. C

    Electric field strength and particle deflection

    Homework Statement A proton enters the gap between a pair of metal plates (an electrostatic separator) that produces a uniform, vertical electric field between them. Ignore the effect of gravity on the proton. a) Assuming that the length of the plates is 11.1cm , and that the proton will...
  49. C

    Where Does the Electric Field Cancel Between Two Unequal Charges?

    Two isolated point charges -7μC and +2μC are at a fixed distance apart. At which point is is it possible for the electric field strength to be zero? I don't know where to start with only 2 numbers and no distances. I know that E= kQ/r^2
  50. C

    Calculating Net Electric Field Strength at Point A

    Homework Statement Find the net electric field strength at point A due to the combined electric fields of both charges. Homework Equations E=kq/d^2 The Attempt at a Solution I know how to solve these type of problems however I'm just wondering how come in the net force line as you...