# electric field Definition and Topics - 434 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. ### 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.
2. ### Modes in a cylindrical dielectric waveguide

I pretend to use the ecuation twice, once for the interior and another for the vaccum, so if I use the cilindrical coordinates for \nabla_t^2 it results in two Bessel equations, one for the interior and another fot the vaccum. In the vaccum, the fields should experiment a exponential decay, in...
3. ### Expression for the magnitude of an electric field

k(q_1-q_2)/(R^2+x^2)^3/2
4. ### Show that the given electric field is a plane wave

A wavefront is defined as a surface in space where the argument of the cosine has a constant value. So I set the argument of the cosine to an arbitrary constant s. ## k(\hat{u} \cdot r - c t) + \phi = s ## The positional information is is in r, so I rearrange the equation to be ## \hat{u}...
5. ### B Distribution of energy in the electric field surrounding an electron

I am thinking about how an electric field has energy associated with it. If a single electron exists alone in a remote vaccuum, I believe it has it's own electric field surrounding it, and that this field has an energy content associated with it. My question is; does this electric field store...
6. ### Uncharged capacitors connected in series

I came across the following explanation from the famous book of Sears and Zemansky which I am unable to understand. I can get the initial part where a positive charge goes to the top plate of C1 since the point a is at a +ve potential causing free electrons to transfer from top plate of C1 to...
7. ### Potential Gradient for individual charges and parallel plates?

In my book, the potential gradient for a charge placed anywhere in space is defined as: E = -V/r HOWEVER, for parallel plate (capacitors) the potential gradient is defined as E = V/d (V being the potential difference). How come there's no negative sign for the potential gradient of the parallel...
8. ### How to create an Electric Field?

Dear friends, First of all I have one question! As per Figure 1, how to implement electrical connection in real life which are seen inside Red Box? and what is the meaning of grounding the other terminal? Figure 1 And the second thing is that, I want to create and electric field on copper...
9. ### Energy within an electric field

I am trying to calculate the energy within an electric field that is generated between two plates by a pulse but am unsure of what voltage value to use. The pulse is a sinc wave. I am assuming I can still use the equation ## E= \frac{1}{2}CV^2 ##. I know the ##V_{rms}## and ##V_{max}## which...
10. ### Can't solve an equation (Deflection of electrons in electrostatic field)

Hello everyone! I've tried everything but the equation (3) in "Deflection of electrons in electrostatic field" is impossible. Can someone at least hint me to a a way the composed it ?
11. ### Concept of electric field and hollow conductors

I think: Due to charge q, there will be a field in region 1, very much dependent on position of q. The inner surface charge density of irregular conductor is also dependent on the position( so that it could cancel the field of charge and E=0 inside body of irregular conductor). The outer...
12. ### Gauss' Law for flux

Hello everybody To calculate the flux for the electric field I need the gauss law. There are two formula one with the integration over some area and the other is Q/e0. When do I have to use which one?
13. ### Electric field lines between a point-charge and a conducting sheet

figure 1: → I don't understand how to approach this problem. Basically it asks for the distance r.I think I should use Gauss's law, but I've been thinking about the shape of the gaussian surface and I'm not sure about how it should look or where I should place it. Any help would be...
14. ### Position for maximum electric field between two wires

For the first part, since $$E(r) \propto \frac{1}{r} \hat{r}$$ by the principle of superposition the maximal electric field should be halfway in between the two wires. Then I'm not sure how to go about the second part of the question. I understand that the total potential due to the two wires...
15. ### Electric field problem using Gauss' law: Point charge moving near a line charge

F = qE ma = (2*10^-6) * (λ / (2pi*r*ε0) ) ma = (2*10^-6) * (4*10^-6 / (2pi*4*ε0) ) => Im not certain what to put for r ( But I sub in 4 because dist is 4) a = ( (2*10^-6) * (4*10^-6 / (2pi*4*ε0) ) )/ 0.1 a = 0.35950 v^2 = U^2 + 2 a s v = 0 u^2 = -2 a s => Can't sqrt negative so i...
16. ### Electric Field Between two Parallel Conducting Plates of Equal Charge

Attached is the subsection of the book I am referring to. The previous section states that the electric field magnitude at any point set up by a charged nonconducting infinite sheet (with uniform charge distribution) is ##E = \frac{\sigma}{2\epsilon_0}##. Then we move onto the attached...
17. ### Equipotentials and Conductors

Here I am going to include the proof provided by my book. It is quite a splendid explanation, though there are a few key points I have yet to fully understand. If the electric force by the electric field on the charge at the surface of the conductor is conservative (which it is), then why is...
18. ### Electric Field inside the material of a hollow conducting sphere

Let's say I place a positive point charge inside a hollow conducting sphere. If we take a Gaussian surface through the material of the conductor, we know the field inside the material of the conductor is 0, which implies that there is a -ve charge on the inner wall to make the net enclosed...
19. ### Electric field in a spherical shell

So for the Gaussian theorem we know that $$\frac{Q}{e} = \vec E \cdot \vec S$$ Q's value is known so we don't need to express it as $$Q=(4/3)\pi*(R_2 ^3-R_1 ^3)*d$$ where d is the density of the charge in the volume. I've expressed the surface $$S=4\pi*x^2$$ where x is the distance of a point...
20. ### Confusion on the distribution of charge

The charges are q1,q2 & q. P,Q,O1,O2 refer to positions only. This is a conducting sphere with cavities containing charges. I'm interested in knowing how the charge should be distributed in the sphere. I know the charges induced on the charges of the sphere should be equal and opposite to the...
21. ### Electric field produced by a uniform charge density on a wall

I couldn't solve the question. Can you help me?
22. ### What I do not understand about mass spectrometers

I try to do my assignment which is based on mass spectrometer entirely. The mass spectrometer i am working on has these parts below: 1.Accelerator region 2.Velocity selector region 3.Spectrometer The elements i am working on are isotopes of the same element and they all enter the accelerator...
23. ### How can electrons flow all the way through the circuit?

Electric currents and the things within are generally explained through the help of intuitive water current examples, where potential difference is explained through the pressure difference and electric current is explained as the flow of water. But I like to think in terms of some driving force...
24. ### Electric field at (0,0) for this charged square conductor

Can we assume that square charge resembles a sphere shell, and think like electric field at sphere shell's center is 0.
25. ### Modulus of the electric field created by a sphere

I think the right solution is c). I'll pass on my reasoning to you: R=6\, \textrm{cm}=0'06\, \textrm{m} \sigma =\dfrac{10}{\pi} \, \textrm{nC/m}^2=\dfrac{1\cdot 10^{-8}}{\pi}\, \textrm{C/m}^2 P=0'03\, \textrm{m} P'=10\, \textrm{cm}=0,1\, \textrm{m} Point P: \left. \phi =\oint E\cdot...
26. ### Potential at a point

I thought the right choice was d). But when it comes to the solutions, it is b) and I don't understand why. My reasoning would be: the potential at a point is the work that the electric field does to transport a charge from infinity to that point, so if the field is zero, it does no work and...
27. ### Electric field and electric potential exercise

a) \vec{F}=\vec{E}\cdot q \phi =\oint \vec{E}d\vec{S}=\oint \vec{E}d\vec{S}=\underbrace{\oint \vec{E}d\vec{S}}_{\textrm{FACES } \perp}+\underbrace{\oint \vec{E}d\vec{S}}_{\textrm{FACES } \parallel}=0+\oint EdS\cdot \underbrace{\cos 0}_1= E2S \dfrac{Q_{enc}}{\varepsilon_0}=\phi \left...
28. ### Parameterize Radial Vector of Electric Field due to Spherical Shell

Homework statement: Find the electric field a distance z from the center of a spherical shell of radius R that carries a uniform charge density σ. Relevant Equations: Gauss' Law $$\vec{E}=k\int\frac{\sigma}{r^2}\hat{r}da$$ My Attempt: By using the spherical symmetry, it is fairly obvious...
29. ### I don't know how to get the x-y direction of position P

Please help me to find the position P and whether it will work in this solution by knowing the position. (The question, my solution and thought in the image)
30. ### Electric Field's Force on a Suspended Plastic Ball

Hi,I couldn't do this problem.I hope someone could help meths is my first time in this forum