# Questions tagged [electric-fields]

For questions that utilize the concept of electric fields (commonly denoted by the letter E), or for questions whose answers likely involve electric fields. More specific than the [electricity] tag, as questions about the phenomenon & theory of electricity do not necessarily involve the discussion of fields.

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### How does one derive the electric potential from an electric field?

I'm trying to work through the full derivation to find the equation $$\underline{E}(\underline{r}) = -\underline{\nabla}V$$ where V is the electric potential and E is the electric field strength. So ...
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### Magnetic field direction [closed]

If the direction of the magnetic force is up along the page or screen and an electron is travelling towards the left along the page or screen, which way is the direction of the magnetic field?
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### Why can't I see any bubble in my anode during my electrolysis experiment

I am doing an electrolysis experiment using this apparatus The left side is the anode and the right side is the cathode. I am using two 9v battery in series (total 18V DC) to power my apparatus. ...
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### CRT electron gun

In CRTs, how does the control grid determine the current of electrons when its voltage is very low compared to the anode? And shouldn't it control the velocity of electrons rather than the current ...
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### How does an electric dipole lose its energy while aligning with a uniform electric field?

How does an electric dipole lose its energy while aligning with a uniform electric field--through heat or light?
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### Faraday's law of induction applied onto a magnetic film

Situation: Consider an infinite magnetically active film with the film normal in the z-direction and thickness $h$. The dynamic magnetization inside the film is $\mathbf{m}=(0,m_y,0)e^{i\omega t}$. ...
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### Magnetic forces on charges

For a charge that sits in an external magnetic field without moving, why is there no magnetic force on the charge?
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### Problem in finding the divergence at a point [duplicate]

I am solving a problem given as Divergence of $\frac{\textbf{r}}{r^3}$ is a) zero at the origin b) zero everywhere c) zero everywhere except the origin d) nonzero everywhere The answer is given as (...
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### Ramsauer–Townsend effect and Thermal Runaway in Thyratrons / (vacuum tubes)

A few years ago an EE told me that the Townsend effect was involved in thermal runaway within vacuum tubes. I can't seem to find any specifics on this on the internet. Can anyone disprove / verify and ...
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### Between 2 electrically charged plates, can the speed of particle depend on distance between the plates? (Refer to image)

Now I understand that $\text{work}=KE$ and this will give the formula for speed as $$v=\sqrt{\frac{2qV}{m}}$$ My question is can’t the $V$ be replaced by $Ed$ since $V=E/d$?
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### Angle between dipole moment and Electric field

I was learning the potential energy of a dipole because of torque from Halliday Resnick. In the given diagram, it said that if we move the system anticlockwise then the amount the Work that was done ...
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### Are induced electric fields parallel or perpendicular to a conductor?

Suppose you have a conductor embedded in a resistor at a 45 degree angle to the (x,y) coordinate axis, and you apply a time-varying, plane-wave magnetic field in the y direction (see Figure 1). As per ...
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### Electric field lines from a non-conductor

I know that electric field lines are perpendicular to the surface of a conductor but I am confused whether electric field lines perpendicular to any surface (non-conductors also)?
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### Electrostatic Shielding due to an Infinite Cylinder

If I place a line charge inside an infinite conducting cylinder which is grounded would the outside be shielded from the electric field inside the cylinder. Also would the potential outside the ...
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### Electric Field due to charges inside cavity

Imagine a conducting body as shown: A positive charge +q is placed inside the cavity of the body. Now due to induction a negative induced charge -q has appeared on inside surface of cavity. Is the ...
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### Electric field flux through the cubic with surface density of charge [closed]

first of all I want you to excuse me for my level of English. I'm doing a homework on Gauss's law, specifically on how to calculate electric flux through a cubic surface. Below I put the complete ...
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### How should one visualize the *electric field* formed from a point charge moving at constant velocity?

So we all know how the magnetic field looks like ( qv x r ) While trying to visualize the electric field I got a little bit confused. Because we are not in electrostatic anymore I don’t know if I can ...
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### Electric field outside a dielectric

Been thinking about this(the question) for quite some time. Is it necessary that even in non-symmetrical cases the dielectric medium will not have any effect on the electric field outside it. Although ...
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### Query on Uncertainty Principle

Consider a universe with only 1 electron. We can't know the position and momentum both of this electron, but we can measure the electric field at each point and since the only thing in the universe is ...
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### When do we use the formula $E=kQ/r^2$?

A cube of side 20 cm has its center at the origin and its one side is along the x-axis, so that one end is at x = +10cm and the other is at x = -10cm. The magnitude of electric field is 100 N/C and ...
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### Hollow charged spherical shell with charge in the center and another charge outside

I came across this question : A thin metallic spherical shell contains a charge $Q$ on it. A point charge $q$ is placed at the Centre of the shell and another charge $q1$ is placed outside it. All ...
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### What would be the capacitance of an unequal charged capacitor?

I searched for this question but I cannot get satisfactory answer. Say if we have a parallel plate or cylindrical capacitor and if I supply unequal charge to it how could I find its Capacitance. We ...
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