# Questions tagged [charge]

A fundamental property of matter which causes it to experience electromagnetic forces.

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### surface charge density $\hat{\rho}$ and surface current density $\hat{\mathbf{j}}$

I am currently studying the textbook Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, 7th edition, by Max Born and Emil Wolf. Page 5, chapter 1.1.3 ...
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### What does the notation $|\text{grad} \ F|$ mean?

I am currently studying the textbook Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, 7th edition, by Max Born and Emil Wolf. Page 5, chapter 1.1.3 ...
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### Why can't we image an insulating meterial with an SEM?

I know that insulating materials are difficult to measure for insulating materials because there are charging. The effect is a drift or a moving micrograph. Why does charging cause a drift in the ...
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### I've got interesting problem from Russian school physics olympiad [closed]

I've been trying to solve this really hard problem (only for me maybe :) from Russian school olympiad for 1 week and I stucked. I tried to make some equivalent electric circuits, but I always end up ...
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### I have a doubt regarding electric field inside uniformly charged spherical shell

A spherical shell, uniformly charged, exerts no field inside it ; the point being either at centre or off-centre. According to Gauss law if we construct a spherical Gaussian surface all inside the ...
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### Charge transfer in two different metals by touching them

When we touch two metallic conductors one is neutral and other has excess of charges, Case 1- Both metals are of copper, then we can calculate actual charges on them at steady state by capacitance ...
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### Magnetic field and frame of reference [closed]

A charged particle moves with a velocity near a wire carrying an electric current,and suppose I see the particle from a frame moving with same velocity in the same direction . I will see the charge at ...
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### Negative test charge Electrostatics

Will there be any significant change (if any) in the formulas of electrostatics, if we use a negative test charge in the derivation. thanks for the help appreciate
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### Why would the two areas not shrinking together cause the total charge to become infinite?

I am currently studying Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, 7th edition, by Max Born and Emil Wolf. Chapter 1.1.3 Boundary conditions at ...
40 views

### Why do electrons flow in the opposite direction of the electric field?

I was taught that the potential decreases in direction of electric field but when we place a positive charge in between it's electric field is too in that same direction but the negative charge has ...
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### Difference between ions, free electrons, and excess charge

This part from University Physics turned my world upside down. What is the difference between ions, free electrons, and excess charge? Also, ions and free electrons make up a neutral conductor? Bloody ...
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### Battery as charge separating factory

I like to think of electric battery as charge separating factory (similar to Van de Graaff generator). I took this idea from "Matter and Interactions" by Chabay and Sherwood. With this view ...
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### Why doesn't a chemical reaction occur with the movement of electrons in the context of electricity?

In school it is generally taught that the movement of electrons between two atoms causes a chemical reaction. However, when it comes to electricity why doesn't a chemical reaction occur with the ...
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### Is it possible, that just as a boson of mass exist (Higgs boson) a boson of charge exists as well? [closed]

If that is the case would it be possible for those bosons to interact with other particles directly? Meaning the field associated with those bosons, interact with the field associated with other ...
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### How to decide which way are the limits of an integral?

So, I'm trying to calculate the electric field at a point $r$ distance away on the perpendicular bisector of a finite line charge having uniform charge density $\lambda$ I arrive at the following ...
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### Computation of the electric potential of a point charge with Dirac delta

As you know, the electrostatic potential for a point charge in free space (at the position $\vec {r_0}=x_0\hat {x}+y_0\hat{y}+z_0\hat{z}$) is given by the relation: V(\vec r)=\frac{1}{4\pi\epsilon_0}...
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### Can electrostatic induction occur between two equal potentials?

Referring to a situation like shown in this basic diagram of electrostatic induction: Does electrostatic induction occur if you have charged objects on both sides of a grounded conductive sphere like ...
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### Does there exist charged BTZ black hole analogue in 1+3D with a negative cosmological constant?

BTZ black holes are defined for the case of 1+2D gravity theory because of closed form computation. I’m wondering if there exist a $1+3D$ analogue black hole? Edit: What I'm actually looking for is ...
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### If charges is quantised, how can we use integrals in electrostatics?

In electrostatics we say that charge is quantised. Then my question is how can we integrate them?
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### If a capacitor is placed inside a uniform electric field (independent of the capacitor), will the formula $U = Q/C$ still hold?

Suppose we have a plate capacitor, placed in a uniform background electric field (in a way that the electric field is perpendicular to the capacitors plates. Without the electric field, the ...
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### Charge tends to accumulate at sharp points

This example is from the book Concepts of Physics by HC Verma. The same example is also present in the book - Fundamentals of Physics by Resnick, Halliday & Walker. Consider two spheres $A$ and $B$...
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### Is there an expression for resistance in a circuit derived from Coulomb's Law?

Coulomb's Law states that the repelling force felt by two charges is proportional to the magnitude of their charges and inversely proportional to the square of the distance between them. Defining ...
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### Formal definition of charge density and current sources in classical electromagnetism

Charge density and current sources are fundamental to classical electromagnetism and appear in Maxwell's equations and everything that comes after. They are intuitive, charge density is a scalar field ...
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### Positive mass but negative/positive/neutral charge

I have heard that the mass of a particle can't be negative because the hamiltonian should be bounded from below. What is the formal argument regarding this and why the same argument doesn't follow ...