What is Electric fields: Definition and 506 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. davidj

    Magnetic and Electric Fields problem

    Would i assume that fg = fm (force gravity holding straight wire down is equal to the magnetic force) and isolate for I? Help if you're available please!
  2. M

    How do I incorporate electric fields into capacitors?

    I know that I’m supposed to use proportional reasoning, but where does electric field even fit in? For whatever equation, I know I’m supposed to see how increasing the voltage by either 2 and 4 volts related to electric field. If electric field is the same as “U”, then wouldn’t it be...
  3. P

    I Defining the Forces from Magnetic Fields and Electric Fields

    We define Electric Field Intensity vector at a point as the force experienced by a unit positive charge kept at a point. Is it correct to define B vector similarly that is, is B vector the magnetic force acting on an unit magnetic north pole and is it correct to call B vector Magnetic Field...
  4. LarryS

    I EM Four-Potential and INDUCED Electric Fields

    Say we have a long solenoid with a current that is fluctuating in time. Then the changing magnetic flux in the solenoid will induce an electric field around the outside of the solenoid (Faraday's Law). This induced electric field is not conservative and therefore cannot have a corresponding...
  5. V

    I Induced electric fields and induced magnetic fields confusion

    So changing magnetic fields induce electric fields (Faraday's law when the magnetic field is changed by either moving the source or by changing the current in the source that's causing the magnetic field, ie. we're not moving the conductor where an emf is induced so there's no f=qvXB). Also...
  6. Javelin

    A Quantum Properties of Quasi Static Electric Fields

    Assume I could produce a stream of calcium ions from a 2nm diameter nanotube by pushing them through the nanotube using coulomb repulsion. Assuming these coulomb repulsed ions produce a stream of entangled ions which then create a slowly emitting quasi static electric (near) field. Even if...
  7. A

    I What is wrong with crossing electric fields? Why can't you sum them?

    I do not understand why electric fields cannot cross. Can't you just sum the two electric fields vectors to get a net electric field?
  8. maayan_aloni

    I Exploring Oscillating Electric Fields for Dipolar Molecules

    Hi all! I was wondering, Is it possible, given a specific dipolar molecule, to create the perfect oscillating electric field so as to heat it and not, i.e. the water around it? What I'm basically asking is could there exist a specific microwave just for X and not all dipolar molecules without...
  9. P

    A Phase diagram of Carbon at large electric fields.

    I am wondering if the phase diagram of Carbon has been explored at very large electric fields. Can one make any theoretical guesses ? In specific I am interested in Pressure Vs Electric field and Electric field vs Temperature at fixed temperature and pressure respectively.
  10. jaketodd

    B Do contracting muscles emit electric fields?

    I bought an EMF meter that can discriminate to electric fields, and it is highly sensitive to the proximity of my body. What is it in the human body that emits electric fields? Is it muscle activity? Maybe many things in the body? Thanks.
  11. A

    MHB Multiple choice question about electric fields and magnetic fields

    Consider a region where a 25-volt-per-meter electric field and a 15-millitesla magnetic field exist and are along the same direction. If the electron is in the said region, is moving at a direction 20 degrees counter-clockwise from the direction of the magnetic field, and is experiencing a total...
  12. Magnetons

    Electrons in Electric Fields: Examining Changes

    What changes occur in electron, whenit through in a electric field
  13. S

    Electric fields of charged plates

    I thought it might be the case that the "2m away" wasn't applicable as the electric field doesn't change if the point away is less than the length of the plate, so I thought I should use the equation listed. All examples I can find talk about two charged plates, or the effect on cylinders...
  14. L

    I Permittivity as a tensor

    If I have an anisotropic material with permittivity: $$\epsilon= \begin{pmatrix} \epsilon_{ii} & \epsilon_{ij} & \epsilon_{ik} \\ \epsilon_{ji} & \epsilon_{jj} & \epsilon_{jk} \\ \epsilon_{ki} & \epsilon_{kj} & \epsilon_{kk} \\ \end{pmatrix} $$ What exactly does each element represent in this...
  15. F

    Magnetic and electric fields in relativity

    I started from: $$\frac{d}{dt}(m\gamma v_x)=qE\ \ \ \rightarrow \ \ \ m\gamma v_x - p_{0x}=qE(t-0)\ \ \ \rightarrow \ \ \ m\gamma v_x=qEt+p_{0x} $$$$\frac{d}{dt}(m\gamma v_y)=0\ \ \ \rightarrow \ \ \ m\gamma v_y -p_{0y}=0\ \ \ \rightarrow \ \ \ m\gamma v_y = p_{0y}$$$$\frac{d}{dt}(m\gamma...
  16. R

    Electric Fields with Motional EMF

    Suppose I have a wire loop that I am moving away from a very long wire which carries a current upward and I want to find the induced current in the loop. The way I know how to approach this is with either Faraday's Law or motional EMF. My question concerns the motional EMF approach. My...
  17. Stephen Bulking

    Lightning rods and Corona Discharge

    1) Q: Why does lightning strike high and sharp targets like a lightning rod? A: Assuming that there is a massive collection of charge, possibly in clouds of a thunderstorm, trying to get to the ground where there is a pool of the opposite charge through an insulator that is air. I believe this...
  18. D

    Exploring the Interaction of Magnetic and Electric Fields

    Hello, If you have an appropriately oriented conductive ring in a constantly changing magnetic field, current will flow in the ring. There will also be a magnetic field associated with the current in the ring. I understand (maybe ... ) that the current is due to the electric field which is...
  19. B

    Electric Fields: calculate the resultant force

    Summary:: I try to find the resultant force on "q". I think I have to find the value of Q, but I'm not sure. I Know F1 = k|q * 2Q| / 3² and F2 = k|q * Q| / 2² Hi, this is my first post on this forum I hope I posted in the right section. I try to find the resultant force on "q". I think I...
  20. Boltzman Oscillation

    Engineering How do I find the electric fields for this capacitor?

    the image is given here along with some numerical information: Now I know that the formula for the electric field in a capacitor is given as: $$E = \frac{V}{d}$$ which I can use to obtain the three following fomulas: $$E_1 = \frac{V_1}{d}$$ $$E_2 = \frac{V_2}{d}$$ $$E_3 = \frac{V_3}{d}$$ where...
  21. S

    How to measure electric and magnetic fields in asymmetric capacitors?

    Summary: I need to build an asymmetric capacitor, but the mathematics of electromagnetics become too tough, do you have any info that can help? Appreciate it! Hello, I am an undergraduate student in engineering and I want to build an asymmetric capacitor, so I need electromagnetics which I...
  22. 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...
  23. H

    Strange question about cancelling electric fields

    I am curious about the case where two electric or magnetic fields cancel each other out (I'm assuming this is possible). If a charged particle travels through the region where the cancellation exists, I am assuming the particle behaves as if no field exists. Does that area still have electric...
  24. H

    Do electric fields have their own separate inherent charge?

    I am assuming the answer is NO. I realize that the electric field of any charged object has an energy density, but I was curious to know it that same field has it's own 'charge density' so to speak, and that it would have a small secondary electric field of it's own. This would imply that...
  25. H

    Energy Density of Electric Fields: Is it the Sum of All Electrons?

    I understand that the energy of an electric field arises from the work put into gathering the electrons together to create the field. Bringing electrons close together requires energy because they naturally want to repel. This potential energy is stored in the field itself and the field has an...
  26. A

    Acceleration of an electron due to Magnetic and Electric fields

    I figured that we would simply add up the forces acting on the electron (the electric force Fe and the magnetic force Fb) and then equate this to the given acceleration multiplied by the mass of the electron like so. vector Fe + vector Fb = (mass of electron) (vector acceleration) since vector...
  27. Boltzman Oscillation

    I GR: Electric & Magnetic Effects - Consequences

    So I just learned that in general relativity Magnatic and Electric fields are dependent on the observer. What are some consequences as a result?
  28. M

    Electric Fields from Linear Charges

    Homework Statement Am amount of charge Q is uniformly spread over a semi-circle of radius R whose center is located a distance A from the origin. What point charge would have to be placed at the origin so that the E field at the center of the circle is 0? (The open end of the semi-circle is...
  29. archaic

    Electric fields and conductors

    Hello guys! The electric field created by a conductor at a point $M$ extremely close to it is ##\vec{E}=\vec{E_1}+\vec{E_2}## where ##\vec{E_1}## is the electric field created by such a tiny bit of the conductor that we can suppose it to be a plane, and since ##M## is extremely close to the...
  30. G

    Net Electric field due to 3 charges

    Homework Statement There is a 3nC charge at (-3,0), -6nC at (0,2) and 5nC at (1,0). What is the electric field at the origin (0,0)? Homework Equations ##E = \frac{Q}{4 \pi \epsilon_0 r^2}## The Attempt at a Solution i think its ##(\frac{1}{4 \pi \epsilon_0})(-\frac{14}{3} i - \frac{3}{2} j)##...
  31. B

    Dipole problem with electric fields

    Dipole problem (which is solved through mirror imaging) has been troubling me with its solution. I understand everything except how the dipole moment's coordinates came to be, since when converted into x-y axis, its doesn't make sense. (problem 4.6) The screenshot contains the solution which...
  32. 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...
  33. J

    B Electric Field in Accelerating Elevator

    According to an inertial observer the electric field of a charged ball sitting on the floor of an accelerating elevator is contracted more than the elevator is contracted. So the inertial observer concludes that an observer inside the elevator will measure that the Coulomb-force from the ball is...
  34. A

    Finding Equilibrium in Electric Fields of Two Charges

    Homework Statement An electric field is created by an uniform linear charge with a linear charge density is 40 nC/m. Find the potential difference between the two points, one of which is situated 5 cm from the line charge and the second at 10cm. Two charges, q and -3q, are situated at a...
  35. Ignitia

    Calculating accelerations in Induced Electric Fields

    Homework Statement Over a region of radius R, there is a spatially uniform magnetic field B →. (See below.) At t =0, B=1.0T, after which it decreases at a constant rate to zero in 30 s. (b) Assume that R=10.0cm. How much work is done by the electric field on a proton that is carried once clock...
  36. D

    Calculating the magnitude of the total electric field at P

    Homework Statement Two electric charges each produce electric fields. At a certain point in space P, the electric field due to the first charge has a magnitude of 8 N/C, and points directly to the right. The electric field at that point due to the second charge has a magnitude of 3 N/C, and...
  37. A

    Determining the direction of electric field lines

    In general, the field lines points away from the positive charge and toward the negative charge. The answer is letter E, but the second part of the answer says, "the magnitude of q1 is less than the magnitude of q2". Is that because q1 is negative and q2 is positive?
  38. radiant_june

    Parallel plate electric fields -- # of electrons transferred

    Homework Statement An oil droplet is suspended between two horizontal parallel plates with a separation of 0.4 cm. If the potential difference of 320V is applied to the plates, determine the number of electrons transferred to/from the droplet. Given/Known Values mdroplet = 5.2×10-6 kg d = 0.4...
  39. Roverse

    An equilateral triangle's electric field at its center

    Homework Statement Three 18-cm long rods form an equilateral triangle. Two of the rods are charged to +10 nC, and the third to - 10 nC. What is the electric field strength at the center of the triangle? Homework Equations $$ \vec{E} = \frac{k*q}{r^2} $$ The Attempt at a Solution 1. Draw...
  40. M

    Electric field vector in component form

    Homework Statement A -12nC charge is located at (x,y) = (1.0cm, 0cm). What are the electric fields at the positions (x,y) = (5.0cm, 0cm), (-5.0cm, 0cm), and (0cm, 5.0cm)? Write each electric field vector in component form. Homework Equations E=k(q/r2) The Attempt at a Solution I was able to...
  41. Hiero

    Does the superposition of electric fields not hold for moving charges?

    If a single point charge is moving, then the component of the electric field normal to the motion is larger (by the gamma factor) than if the charge were stationary. Now consider an infinite line of charges (with a small separation, the same between each charge). If the whole line is moving...
  42. aatari

    Electric Fields - Electron Passing through deflecting Plates

    Hi Guys, I have attempted the question below. Please have a look at my work and let me know if everything looks fine. Any feedback would be great. 1. Homework Statement Homework Equations F = qv/d a = F/m t = d/v qv = 1/2mv^2 x = vt + 1/2 at^2 The Attempt at a Solution
  43. B

    Induction via Infinite sheet of Current

    My thoughts are concerning an infinite sheet carrying current in a direction. I wish to induce a unidirectional electric field outside of the sheet via induction. My ideas were that if the current was changed linearly in a sawtooth fashion, then I would achieve the induced electric field in...
  44. C

    Lateral electric fields in a lateral electrostatic actuator

    Hello, I'm reading through section 6.2.2 of https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-013-electromagnetics-and-applications-spring-2009/readings/MIT6_013S09_chap06.pdf on page 157. I understand all the math, but I have a conceptual questions that I don't seem to...
  45. C

    Motion of Charged Particles in Electric Fields

    Homework Statement This is the question: An electron at rest of mass 9.11 × 10−31 kg is accelerated through a potential difference of 350 V. It then enters some deflecting plates of 50 V with dimensions as shown. Calculate the distance x (deflection of the electron) (Charge on an electron is...