# Tagged Questions

Electric field is defined as the electric force per unit charge.

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### Motion of a dipole in an electric field

Assume that we have some non-constant electric field $E(x,t)$ and a point-dipole at a position $q$ with a constant dipole moment $\vec{p}$. How would you describe the time evolution, i.e. the motion ...
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### Do electric fields generated by plane charges lose intensity over distance? If not, why?

Sparknotes' studyguide for the SAT II: Physics test says that for a point charge (1-dimensional, e.g. an electron), the formula for intensity of the generated electric field is given by ...
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### A question about electric field

I would like to understand why is it the charge density while dealing with currents is $\mathop{\mathrm{div}}(E)/4\pi$, while when dealing with insulators is $-\mathop{\mathrm{div}}(E)/4\pi$? Thank ...
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### Want to achieve maximum magnetic force & find out the max point [closed]

Hi Sir/ Madam Want to achieve maximum magnetic force & find out the max point for this setting, want to know is the strongest magnetic force must in the 'dot' area ( middle poin of setting ) ...
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### What is the true electric potential at the terminals of a battery?

I recently studied Laplace's equation and numerical methods for solving it, and so I'm trying to simulate an electron gun. (assuming cylindrical symmetry on the Wehnelt, anode, and beam.) The setup ...
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### How/Why does voltage reflect?

I'm trying to understand antenna theory again, and I'm again stumped by the concept of VSW (voltage standing waves). I understand standing waves, I remember these from a physics clases, however I do ...
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### Static electricty and fields inside of the conductor?

I have a few related questions about static electricity and conductors. 1. when we say static electric field inside a conductor is zero, let us take an example of two concentric conductors, outer one ...
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### How can there be a Current and an Electric field in an idealized wire with no voltage drop?

In an ideal circuit, How can there be a current b/w points a & b, when there is no potential difference and thus no electric field between a & b? If there is no current, then where does ...
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### Force on an electron at an arbitrary point inside a cylinder (electron gun)

I want to simulate the path of an electron through the anode of an electron gun. I therefore need to calculate the force on the electron due to the electric field from the anode and apply that to its ...
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### Materials in Electrostatics [closed]

A point charge $q$ is placed at the centre of a sphere of linear dielectric material of permittivity ε. The sphere is of radius $a$ and is placed in a vacuum. How would I go about finding the ...
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### Are dc and ac currents produce electric field?

I have four different situation and i want to learn what kind of field (electric or magnetic) each produces and which produces electomagnetic waves? 1)dc current flow in a conductor 2)ac current ...
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### Do really, two oppositely charged bodies (of equal charge in magnitude) attract each other?

It is well known fundamental behaviour that, oppositely charged bodies attract each other (I don't know whether it applies also for charges of equal magnitude or not), and identical charges repel each ...
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### If we change the radius of spherical surface does electric field or flux change?

Suppose a point charge is located at the center of a spherical surface. The electric field at the surface of the sphere and the total flux through the sphere are determined. 1).What happens ...
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### Electric field lines density

When we're dealing with problems in electrostatics (especially when we use Gauss' law) we often refer to electric field lines density which is inversely proportional to radius in case of a single ...
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### Why does the voltage increase when capacitor plates are separated?

In lab, my TA charged a large circular parallel plate capacitor to some voltage. She then disconnected the power supply and used a electrometer to read the voltage (about 10V). She then pulled the ...
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### how does an electric field comes inside a conducting wire inside the circuit?

This has been a really great confusion for me now .... Many places i have read in books that when a potential difference is applied across the ends of a wire a constant electric field is generated ...
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### What are the fields produced around a current carrying conductor?

If you consider a current carrying conductor, every instant an electron enters the conductor, another electron will be leaving the conductor. Thus, the current carrying conductor will not be charged ...
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### Can the magnetic lines of force of two or more magnets intersect each other?

I know the basic property of magnetic lines of force,that they can never intersect each other.But,I don't know whether it mean -magnetic lines of force of same magnet can't intersect each other,but ...
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### Electric fields between 2 spheres with different voltages [closed]

Consider two spheres, both with the same diameter. Case 1: sphere A is 100v, sphere B is 0v Case 2: sphere A is 50v, sphere B is -50v Which case has the higher electric field? Electric potential ...
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### How does electromagnetic induction happen?

Electric and magnetic fields are different from each other(i think i am correct).. How does changing magnetic field induce electric current???
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### Calculating Electric Field from a Potential Difference w/o Charge

So here is my homework question: Two long cylindrical shells of metal (radii $r_1$ and $r_2$, $r_2 > r_1$) are arranged coaxially. The plates are maintained at the potential difference ...
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### Variation of electric field and current flowing

Theoretically, a change in either electric or magnetic field will cause a current to flow , I am already familiar to Faraday's law of electromagnetic induction, so I tried to search about producing a ...
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### What does the complex electric field show?

We have a complex electric field. Is there any definition for absolute and imaginary part of a complex electric field? What do they stand for?
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### How would charge be distributed in charged conductors if the Coulomb law was not ${1}/{r^2}$?

Would the excess charge on a conductor move to surface until the electric field inside become zero if the Coulomb law was for example $\frac{1}{r^3}$? If yes, would the distribution $\sigma(x,y)$ be ...
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### Electric Field Between Two Parallel Infinite Plates of Positive Charge and a Gaussian Cylinder

Is the electric field between two positively charged parallel infinite plates one with a charge density twice the other effect the electric field on the outside of the plates? I am thinking no, ...
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### Questions on electric field formed in conductor and the magnetice field it moves through

When a conductor (e.g. a wire) is moving through a uniform magnetic field, it will create a electric field in the wire as the magnetic field exerts a force on the moving conduction electrons in the ...
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### Non-conservative electric fields due to changing magnetic flux?

What I read in several places, tells me that, the fact Coulomb's Law follows inverse-square law and gives a force which is radial, implies that a static electric field must be conservative.(In short, ...
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### Why the electric force does no work on the charge when perpendicular to the field?

I was reading my physics textbook and came across this sentence: When a charge moves in an electric field, unless its displacement is always perpendicular to the field, the electric force does ...
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### Need a more efficient way to find where the $E$ field is zero

So this is a problem I already know how to solve, but I feel like my method is really inefficient and I'm wondering if there's a more intuitive, less tedious way to arrive at this conclusion. If we ...
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### Calculate electric potential and electric field of uniformly charged wire

Say you have a uniformly charged straight wire of length $2L$ going from $-L$ to $+L$ along the $z$ axis with its midpoint located at $z=0$. What is the electrostatic potential, in cylindrical ...
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### insulator based gauss law questions

My book is incredibly scarce on insulator based Gauss law questions. Conductors seem to handle themselves pretty simply. Here's a question I'm working on that isn't part of my book. where the radii ...
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### Electric field outside a sphere with a cavity

I have a sphere of radius $2a$ centered at the origin and made of a nonconducting material that has a uniform volume charge density $\rho$. A spherical cavity of radius $a$ eccentric to the right side ...
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### Cylindrical charge distribution [closed]

I'll just list the problem first and then explain what I need help with. Consider a cylindrical charge distribution extending from $r = 0$ to $r = 8.2$cm of charge density $\rho = r/a_0$, where ...
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### Determine the total charge needed to apply to the electroscope

A large electroscope is made with "leaves" that are $78$-cm-long wires with tiny $24$-g spheres at the ends. When charged, nearly all the charge resides on the spheres. If the wires each make a ...
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### Does the electric field change only inside the dielectric, or even after exiting the dielectric?

I know that the field inside a dielectric is changed and is $\epsilon$ times less the original field (some books use $K$ for this constant). This is because the induced field inside the dielectric is ...
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### Voltage and parallel-plate capacitors

Suppose we have two parallel plates (each of area $A$) spaced with distance $d_1$ acting as a parallel-plate capacitor within a circuit. If the capacitor is connected to a power source with constant ...
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### Conceptually, why does an electric field not require a charge flowing through it?

My son has been asking me a lot about electromagnetism and so I got to read up on it.One of the interesting and hard to grasp (for me at least) concepts is that an electric field will exist even when ...
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### Projectile motion of a charged particle in a homogeneous electric field

I'm reading an article about projectile motion, but I'm having some trouble with how the author found the equations of motion when a homogeneous electric field is considered. To allow an immediate ...
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### Inductor rise time and inductor wire length

So here is an interesting question about inductors or coils in general. Suppose you had a inductor which was 12 inch's in diameter and say 12 inch's in length and has 100 turns of wire. The total ...
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### Electric field. Linear charge density

I was wondering if anyone could help me out in this exercise I've been struggling to solve. A straight, nonconducting plastic wire $8.50 cm$ long carries a charge density of 175 $nC/m$ ...
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### Cause of electromagnetic induction?

The rate of change of magnetic flux through a surface (open) is related with the line integral over the closed loop binding the selected surface by one of the Maxwell's equation. But that means even ...
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### Using the image charges method to find the electric field

The following is a question from a tutorial in my Physics 2 course about conductors and the Method of image charges. We are given two infinite perpendicular and grounded plains. The first ...
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### Why does the electric field perpendicular to every point on the surface of a conductor?

I am reading Berkeley Physics Course, Volume 2 (Electricity and Magnetism by Edward M. Purcell). I am in chapter $3$ pg $92$, and the book discusses conductors. The following is from the book: ...
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### Drawing electric field lines-Equations or software

Shown below in the diagram are two conducting material connected to a battery source and vacuum OR air is in between them. There will be charges developed on their surfaces. I am interested in finding ...