Electric field Definition and 1000 Threads

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. D

    Amplitude of an oscillating electric field

    Homework Statement: The amplitude of the oscillating electric field at your cell phone is 4.0 μV/m when you are 10 km east of the broadcast antenna. What is the electric field amplitude when you are 20 km east of the antenna Homework Equations: electric field i've done E=##\frac A...
  2. D

    Electric field in the narrow wire

    i've started from this I1=I2 then I1= JA1=##\frac {E l} R## I2= JA2=##\frac {E_2 l} R## but can't get anything useful relating them. Am i forgetting any other useful formula? I get as result E4
  3. A

    Electric Field for the circular path of a positively charged particle

    Here is picture. Answers is A. My attempt was that I thought if i were to place a positive test charge then it would go from top to bottom if there was a positive charge in the center it was avoiding and a positively charged particle at the top, but an electron at the bottom so it would avoid...
  4. C

    Is the Electric Field Calculation Consistent with the Potential Result?

    Question Part C Part D
  5. C

    Deriving an Expression for an Electric Field along the Z axis

  6. Yalanhar

    Electric Field due a charged disk

    Homework Statement: uniformly charged disk, radius r, with surface charge density ##\sigma## . I want to find the electric field along the axis through the centre of the disk at a h distance Homework Equations: ##dE=\frac {kdq}{r^2}## My Solution: ##dE=\frac {kdq}{r^2}## in this case r=s...
  7. Yalanhar

    Calculate the electric field due to a line of charge of finite length

    Homework Statement: A thin rod of length L and charge Q is uniformly charged, so it has a linear charge density ##\lambda =q/l## Find the electric field at point where is an arbitrarily positioned point. Homework Equations: ##dE=\frac{Kdq}{r^2}## A thin rod of length L and charge Q is...
  8. AndresPB

    Electric Field from its Potential of a Half Circle along its Z axis

    So I figured out the potential is: dV = (1/(4*Pi*Epsilon_0))*[λ dl/sqrt(z^2+a^2)] . From that expression: We can figure out that since its half a ring we have to integrate from 0 to pi*a, so we would get: V = (1/(4*Pi*Epsilon_0))*[λ {pi*a]/sqrt(z^2+a^2)] In that expression: a = sqrt(x^2+y^2)...
  9. N

    Find the Electric Field E using Gauss' Law

    I tried to work out both a) and b), but I am not sure if I am correct. I drew a picture with a sphere around q first with radius r and then with radius 3r. For a) ##E.A=\frac {q}{ε_°}## (when using Gauss' Law) Since ##A=4πr^2##, I substituted this in the equation and solved for E giving me...
  10. adamaero

    By using Gauss' law, can the electric field be p/(pi*ε*r^2)

    Which is better to use? The equation for the area or the circumference of a circle? Schaum's Electromagnetics (4 ed) by Edminister vs http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecyl.html
  11. S

    Electric field due to two positive charges

    I am having trouble solving the following problem. I am given two positive charges on the x axis: I know that the electric field strength at point P is ##E=150 \frac{V}{m}##, ##d=1.8m## and ##a=2.5m##. I want to find the charge of ##Q##. As far as I know, the electric field on the y-axis...
  12. R

    Electric field on a ring's axis

    The contribution coming from a little segment of the ring is ##d\vec{E}=\frac{dQ}{r^2}cos\theta \hat{z}##, assuming that the horizontal components cancel out. But how can we show that?
  13. navneet9431

    Would electric field exist if there were only one type of charge?

    I believe the answer is incorrect, reasons: The answer assumes that electric field will exist . But this is not the case , until and unless there is a bipolarity there cannot be an electric field ( in case of isolated charged objects, the field exists because the bipolarity is separated by a...
  14. Zahid Iftikhar

    Electric Field of a moving charge

    When a charge is at rest, it has an electric field only. When the charge starts moving , it is said to have accompanied a magnetic field. My question relates to its electric field while in motion. Does it still exist or not? I know in electron guns electrons are deflected while passing thru the...
  15. J

    Electric Field for Charge Distributions

    We are given: q1 = +2.0 x 10-5 C, q2 = q3 = -3.0 x 10-5 C, r31 = r21 = 2 m a) We start by finding the electric force between q3 to q1 and q2 to q1 FE31 = k * q1 * q3 / r312 FE31 = (9.0 x 109 Nm2/C2) * (+2.0 x 10-5 C) * (3.0 x 10-5 C) / (2 m)2 FE31 = 1.35 N FE21 = k * q1 * q2 / r212 Since...
  16. P

    Calculating a Non-Uniform Electric Field Given 6 different Electrode Pairs

    I know how to find the electric field of more traditional designs i.e. a sphere, through Gauss' Law but I don't think Gauss' Law applies to this scenario. I tried to separate each part of the electrode into simple spheres and rods and using Gauss' Law to find these individual elements. This...
  17. C

    The source of the electric field of a battery?

    If you place a zinc / copper battery it will create an electric field pointing from the copper to the zinc and my question is this what makes this electric field , the zinc pushes electrons in the circuit and never "stays" negatively charged for an electric field to be created same for the...
  18. S

    Find the charge of a mass hanging from a pendulum in an electric field

    Hi, so I was able to solve this problem by just equating the forces (Tension, mg, and EQ). But I thought I could also solve this problem with Conservation of Energy. However, I calculated it several times, and I never get the right answer this way. Doesn't the Electric Field do the work to put...
  19. Physics lover

    Variation of electric field and potential along the axis of a cone

    Options are at the top of page as a) b) c) d) Answer may more than one. Now since 'a' is distance from the smaller surface of cone so as we move along the axis area will increase,So current charge density will decrease and as we know J=sigma E,E will decrease,but V will remain constant since...
  20. M

    Electric field in a circuit with a DC source

    So I understand that when an electric field is produced in a conductor of length L, the net electric field in the conductor will be 0 because the rearrangement of electrons in the conductor results in the production of its own electric field which cancels out the one produced initially...
  21. T

    Solving for Electric Field at an Angle: Ex = 10.0V/m

    Ex =10.0Vm-1 dx= d2=x2+y2 x=4.00m y=3.00m d2=4.002+3.002 d=5.00m Ex = -dV/dx 10.0Vm-1=-dV/5.00m 10.0Vm-1*5.00m=-dV -50.0V=dV So from origin at 100V-50.0V = 50.0V But the solution I am given gives the answer at 50.5V and the information "directed at 45.0◦ " does not seem to have been used so may...
  22. T

    Plasma ball radio-frequency energy

    I read Wikipedia's description of how a plasma ball works. Question: What kind of energy is the "radio-frequency energy from the transformer"? Is in the form of electric field energy, magnetic field energy, or both? Thank you! (from Wikipedia)... Although many variations exist, a plasma lamp is...
  23. Pushoam

    The electric field inside and outside of a dielectric

    I bring a dielectric in a region with electric field ##\vec E_0##. Net electric field ## \vec E_{net} = \vec E_0 + \vec E_p ## , where ## \vec E_p ## is electric field due to polarization of dielectric. For linear dielectric, ## \vec E_p ## is 0 outside the dielectric. So, ## \vec E_{net} =...
  24. alexmahone

    Average electric field over a spherical surface

    I'm sure the average is going to be an integral, but \displaystyle\frac{1}{4\pi R^2}\oint\mathbf{E}\cdot d\mathbf{a} gives me a scalar, not a vector.
  25. M

    Finding the maximum value of the electric field

    I tried to find it the following way but to no avail: Let maximum value of ##\sigma## be ##S## Now unfortunately, we do not have a maximum value for ##\dfrac{1}{r^2}## because the field point can be as close as we want to the arbitrary surface charge. (The field at a point on the surface is...
  26. Kasiopea

    Why is the x-component of the electric field at point P positive?

    I got the answer: E(P)=(k*Q)/(3î )−(k*Q*ĵ) /2 Can someone confirm if this is the right answer?
  27. jmemo

    Find the direction and magnitude of an electric field

    Find the direction and magnitude of an electric field that exerts a 4.65 ✕ 10−17 N westward force on an electron. (Enter the magnitude in N/C.)
  28. R

    Divergence of an Electric Field due to an ideal dipole

    Given $$\vec E = -\nabla \phi$$ there $$\vec d \rightarrow 0, \phi(\vec r) = \frac {\vec p \cdot \vec r} {r^3}$$ and ##\vec p## is the dipole moment defined as $$\vec p = q\vec d$$ It's quite trivial to show that ##\nabla \times \vec E = \nabla \times (-\nabla \phi) = 0##. However, I want to...
  29. somasimple

    Ion migration by diffusion in an electric field

    Hi, A solution contains some ions (charged particles). We are only interested in my exemple to positive ions. It is assumed that these ions acquired some mobility under a concentration gradient. Their direction is A to B. Then these ions encounter/cross an electric field which is oriented from B...
  30. M

    What will the electric field be at the surface?

    The electric field due to a dipole distribution in volume ##V'## can be viewed as electric field due to a volume charge distribution in ##V'## plus electric field due to a surface charge distribution in boundary of ##V'##. ##\displaystyle\mathbf{E}=\int_{V'} \dfrac{\rho...
  31. Gnall

    How could I find the total electric field in this question?

    The electric field due to the semicircle is 2kQ/pi.Rsquare Sorry for the bad english.
  32. peguerosdc

    [Griffiths ex4.2] Electric field of a uniformly polarized sphere

    Hi! This is more a conceptual question rather than the calculation itself. So, Griffiths' section 4.2.1 "The field of a polarized object / Bound charges" says that if you want to calculate the field produced by a polarized material, you can find it from the potential of a surface charge and a...
  33. P

    Electric Field Lines: Should Earthed Plate Have No Charge?

    Shouldn't the plate that is earthed be with no charge? making B correct. but the accepted answer was A.
  34. cianfa72

    Electric potential difference between a battery's + terminal and the ground

    Hi, I've a question about electricity in the following scenario: consider an accumulator (e.g. a 9V battery) and an analog/digital voltmeter having a probe connected to the accumulator + clamp and the other to the ground (for instance connecting it to a metal rod stuck in the ground). Do you...
  35. Y

    Problem concerning a mass with charge in a homogeneous electric field

    I know how the answer is C, since E=F/q and F=ma=mg. However, I am a bit confused as to why my other method doesn't work. I thought that since the droplets are falling at a constant velocity, there is not net force, so according to E=F/q the electric field must be zero then? This seems like a...
  36. K

    Electric field problem — Changing the charge on two spheres

    Two identical conducting spheres A and B carry equal charge. They are separated by a distance much larger than their diameters. A third identical conducting sphere C is uncharged. Sphere C isfirst touched to A, then to B, and finally removed. As a result, the electrostatic force between A and B...
  37. Zack K

    Electric field of a hollow cylinder

    I uploaded a diagram of the problem. I treated this as many thin rings and integrated it over the length. I placed my origin as in the same place as the uploaded picture. Finding the electric field due to one small ring: ##\vec r =\langle w-x, 0, 0 \rangle## where ##x## is the distance of the...
  38. Moara

    Electric field of a charged cube

    Tried to use gauss law but there isn't any usefull symmetry that I have seen. Also tried to integrate the field due to small charges over the whole cube, didn't work too since the integral were too much complicated.
  39. M

    Question about conservation of angular momentum for charges

    Why is angular momentum conserved for a charge in an electric field?
  40. S

    Help with negative charges in an electric field.

    How can a negative charge move towards a position of a higher electric potential from lower potential but lose electric potential energy?From my understanding, I understand that for a positive charge, it must lose potential energy from the electric field as work is done by the electric force in...
  41. ybisno

    Given Electric field, find the charge densities

    Hi. Need help with physics homework. I was able to separate each term and find sigma from the second term and possibly lambda from the first term. Not sure how to approach the third term. (attached attempt at question)
  42. ybisno

    Given Electric Field, Find the charge densities.... (Electrostatics)

    Hi. Need help with physics homework. I was able to separate each term and find sigma from the second term and possibly lambda from the first term. Not sure how to approach the third term. (IMAGE ATTACHED)
  43. Shohel chowdhury

    Cancellation of the electric field from opposite charges

    Electric field of opposite charges, cancel out each other, is it right?
  44. M

    What should I consider when searching for a high voltage power supply?

    I'm looking for a high voltage power supply. I have no experience with such a power supply, nor with all the terms or specifications used for such tools, so I'm looking for general suggestions to what to look for. I want to generate an electric field or potential field between two points a few...
  45. W

    Working with Electric Field E, not Vector Potential A

    We commonly have E and B defined as: But how can I work in electric field E, instead of vector potential A?
  46. M

    Calculate the energy in a capacitor's electric field

    Homework Statement Capacitor has a charge of 0.008C. Capacity is 2 μF. Need to calculate energy of electric field. Answer: 32J Homework Equations E = q2/2*C The Attempt at a Solution This seems right equation, but instead of 32J I get 16J.. any ideas?
  47. tinesi

    Voltage, electric field and potential energy for concentric shells

    1. Homework Statement the a shell is charged Va=120v shell b is grounded, Vb=0V What is the voltage in the center of shells (vo)? The electric field in the center of shells? The potential energy in the center of shells? Homework Equations Vr=Va+(1/r-1/a)/(1/a-1/b)Vab (from integrals) though I...
  48. solzonmars

    Electric field outside a spherical shell?

    If a charge is put inside a spherical shell, why is the electric field outside the shell independent of the location of the charge? Gauss's law could find that the net flux is independent, but not each individual field? Is this something about the surface charge density being independent of...
  49. A

    What is the electric field of a point charge?

    Assuming the point charge lies at the origin, what is the electric field at the origin? Zero or undefined?
  50. G

    How to treat the "ideal" plate capacitor more rigorously?

    Hi. The derivation of the capacity of an ideal parallel-plate capacitor is inconsistent: On the one hand, the plates are assumed to be infinitely large to exploit symmetries to compute an expression for the electric field, on the other the area is finite to get a finite expression for the...
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