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30
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5answers
3k views

How is it possible to accelerate a neutron?

It is possible to accelerate a charged particle in an electric field, how is it possible to accelerate a neutron? How can we control its velocity?
1
vote
0answers
17 views

Determining if an object is dielectric or metallic

In a worksheet I was given, I had to find the net electric field of P which is L distance away from a bar. The last question is ...
1
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0answers
11 views

Can we use EEG to record signal from spinal cord?

My hype is about the idea that Spinal cord around neck is the place every signal sent to control whole body. So if we can record all signal, we could analyze movement of our body from finger to leg ...
0
votes
1answer
24 views

Gauss Theorem:Electric field of an uniformly charged non-conducting spherical shell

I want to know the electric field of an uniformly charged non-conducting spherical shell. I know that in case of conductors(metals),the sphere can be shell or it can be solid,but in both the cases ...
0
votes
0answers
14 views

What will be the electric field intensity? [on hold]

Ì have a problem here I tried to solve it but I am not able, so it goes like this. If the surface area is 10 cm2 and the electric flux is 25 NM2 C-1, find the electric field intensity?
0
votes
0answers
34 views

Electric Flux. Integral of $E$ with respect to $A$ is equal to TOTAL Electric FLUX? [closed]

The first equality is simple to me but I don't understand the second one,$\oint {\bf E}\cdot d{\bf A}$. And the second second last line is much hard to understand. Could you please give some lecture ...
0
votes
0answers
11 views

A homework about Electric field [on hold]

Set up a uniform electric field between two horizontal plates by charging the lower plate positively and the upper plate negatively. The plates have length L and separated distance d. An electron is ...
1
vote
2answers
39 views

Draw the charge configuration according to the electric field [closed]

I'm trying to draw the charge configuration outside the regions that lead to the given electric field patterns. Can someone show me how?
0
votes
2answers
39 views

What is the difference between electric charge and electric flux?

What is the difference between electric charge and electric flux? According to my knowledge electric flux is nothing but electric charge enclosed by the closed surface.
1
vote
1answer
75 views

Upper limit to electric charge confinement?

The following questions are not intended for conventional capacitors (which stores excess charge on the outside surface), rather a type of hypothetical capacitor which is designed to confine charge by ...
0
votes
1answer
191 views

Apply Gauss' Law to find Electric Field around nonconducting plastic sheets

The question: Two very large, nonconducting plastic sheets, each 10.0 cm thick, carry uniform charge densities $\sigma_1$,$\sigma_2$,$\sigma_3$ and $\sigma_4$ on their surfaces, as shown in the ...
1
vote
2answers
113 views

Why isn't resistance proportional to distance squared

Here we have a wire. At both ends there is an equal and opposite field caused by a chemical reaction. So, if we decrease or increase the distance between the two points, the strength of the field ...
0
votes
1answer
23 views

Find distance with zero net electric force [closed]

I am new to the site (and physics!), sorry if this is too elementary or something. I have this problem that I can not solve - perhaps you could help?! Thank you!
0
votes
0answers
17 views

Finding the contained charge in a box, given the $E$-field [closed]

I'm not sure whether my approach is correct for this problem, it's been a while since I've touched E&M. I thought it best to check, as I'm not sure whether $0$ is the proper answer. I've got a ...
0
votes
1answer
24 views

Why don't neutral atoms distort the electric field?

Suppose I have a positively charged conductor with a cavity. There's a positive charge inside the cavity and the system has reached electrostatic equilibrium. Then there's negative charge surrounding ...
1
vote
1answer
57 views

Microscopic fields inside a conductor

In a neutral conductor if we assume electrons as point charges, the electric field in the space between them cannot be identically zero. This microscopic field may be very weak. What if we were very ...
3
votes
4answers
4k views

Electric field outside a capacitor

I know that the electric field outside of a capacitor is 0 and I know it is easy to calculate using Gauss's law. We create cylindrical envelope that holds the same amount of charges (of opposite ...
8
votes
5answers
8k views

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 ...
3
votes
2answers
87 views

Physical meaning of imaginary part of Electric field?

As far as I know (or I thought I knew), if we have an electric field $$\mathbf{E}=\mathbf{E_0}\cos(\omega t - kx),$$ we can define it as the real part of $$\mathbf{E}=Re(\mathbf{E_0}e^{i(\omega t - ...
1
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1answer
5k views

Potential Gradient & Electric field…

Potential gradient is the negative of the electric field. Does the negative (here) means that its direction is opposite to electric field.? If it does mean this, How is the direction of the ...
2
votes
1answer
114 views

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 ...
0
votes
1answer
36 views

How is the charge concentrated at the centre of shell for calculating potential from it?

While calculating electric potential due to a spherical shell at a point outside the shell, why do we say that the entire charge is present at the centre of shell? Is this true even if the charge on ...
2
votes
1answer
30 views

Vector decomposition validity

Is force or field decomposition into component vectors always valid? Lets say a constant electric field $\vec{F}$ is acting in space such that it makes an angle $\phi$ with respect to the horizontal ...
3
votes
2answers
149 views

How does a magnetic field cause objects to move?

Let me start off by saying that I never got a degree in any field but I do read and study physics (both classical and quantum); although I personally can't solve quantum physics equations I do have a ...
-1
votes
1answer
33 views

Electric Field of a sphere

Is there a point in space where the electric field is half of the electric field on the surface of the sphere? I just got curious if it would be possible.
0
votes
1answer
10 views

How is electric field strength related to potential difference?

I was looking at the derivation of drift velocity of free electrons in a conductor in terms of relaxation time of electrons. Here a metallic conductor XY of length $\ell$ is considered and having ...
2
votes
1answer
58 views

Definition of a field line?

Ok so I finished by A-levels last year (english exams 18 year olds take) and we defined in my physics course we defined field lines (for an electric field) as: The path a free positive test charge ...
1
vote
1answer
38 views

What factors cause the velocity saturation to occur at different electric fields for different materials?

In semiconductors the velocity of carriers gets saturated after a certain value of electric field. In silicon it occurs at around $10^4 kV/cm$ and in GaAs at some other value. What factors are ...
0
votes
2answers
97 views

Does a conductor need to touch the battery terminal for electric field to be set up inside it?

I understand that an electric field is setup inside a conductor when it is connected to the terminals of a battery and that this field is caused by induced surface charges on the conductor. These ...
2
votes
3answers
256 views

Conservation of energy in electromagnetism?

How is energy conserved in electromagnetism? Is it hinted only from Lenz's law or from Maxwell? Also, if a solenoid's flow of current produces a magnetic field, and from the magnetic field forces are ...
0
votes
1answer
74 views

Is there a surface charge density?

Consider a dielectric sphere placed within a dielctric medium. There is a uniform electric field $E_0$ present throughout in the medium. Would there be surface charge on the sphere?
0
votes
2answers
20 views

Direction of current in concentric cylinders

Example 7.2 in David Griffiths E & M book (3rd edition) has a side view of 2 concentric cylinders, with smaller radius $a$ and larger radius $b$. The region in between $a$ and $b$ has ...
4
votes
6answers
5k views

Does a current carrying wire produce electric field outside?

In the modern texts of electromagnetism in the presence of stationary currents the electric field is assumed conservative $\nabla \times E =0 $. Using this we get $E_{||}^{out}=E_{||}^{in}$ which ...
1
vote
1answer
36 views

How to find whether the electric field between capacitor plates is above or below the electrical breakdown limit of the insulator between the plates?

Let's say the two plates of a capacitor have charges $q_1$ and $q_2$. The separation between these plates is $d$. I know that I can calculate the electric field by dividing the voltage that is applied ...
0
votes
0answers
12 views

Measuring polarization of a neutral object near a charged sphere

I am trying to design an experiment where I can calculate the distance at which polarization will not have a measurable effect on a neutral object, from a sphere charged by a Van Der Graaf generator. ...
0
votes
1answer
23 views

The difference between EMR and lone Electric and Magnetic fields

I fail to understand the true difference between EMR and electric and magnetic fields. When current flows, there is an electric field due to the electron flow and a magnetic field, however no EMR ...
1
vote
1answer
1k views

Electric field and insulator or dielectric

I have a uniform electric field $E$ projected from left to right and I placed an insulator or dielectric right in the middle of it. To the left of the insulator, the $E$ is the original $E$. Inside ...
0
votes
1answer
33 views

How does electric field intensity look like along a wire which has one end connected to an AC source and the other one is left free?

How does the electric field intensity look like along a wire with constant conductivity which has one end connected to an AC source and the other one is left free? I mean is the electric field the ...
1
vote
1answer
90 views

Ion Optics: Electric and Magnetic field. A comparison with Light Optics

When we compare ion optics with light optics, normally we consider electric field. For example Snell's law. $n_1\sin\theta_1$=$n_2\sin\theta_2$. When an electron move from one electric potential to ...
0
votes
1answer
136 views

Electric field strength at the center of an equilateral triangle

Questions: Three $x$ m long rods form an equilateral triangle. Two of the rods are charged to $+q$ C and the third to $-q$ C. What is the electric field strength at the center of an equilateral ...
2
votes
1answer
49 views

Proving the equivalency of the potential energy of a system of charges and the work required to assemble a system of charges

This is a very cool, and highly beneficial problem in my opinion. I feel as though truly understanding this proof would broaden anyone's conceptual understanding of electric potential. My textbook ...
1
vote
0answers
60 views

Sign error in calculating the electric field of point charge

I have to determine the electric field of a point charge, I get a true result except for a sign. Here is my passages. $$\nabla \cdot e = \frac{\rho}{\epsilon}$$ $$e = - \nabla u$$ $$\nabla^2 u = - ...
15
votes
2answers
1k views

Why is there no Gravitational Magnetic Field?

We think that the electric field and gravitational field operate similarly with their corresponding charges/masses. With just a difference that the electric field is sometimes attractive and sometimes ...
1
vote
1answer
40 views

Uniformly charged sphere's electric field

I am facing this topic for the umpteenth time in my college career and, of course, every teacher has explained it in a different way. In this course, to find the expression of the electric field of a ...
3
votes
1answer
73 views

Why are atomic quadrupole moments calculated using nuclear spin?

It's my understanding that electric quadrupoles interact with the gradient of an electric field, and I understand roughly how this works. I am trying to calculate the interaction between an atomic ...
2
votes
1answer
28 views

Electric Field-Drift Velocity

Why is the net velocity of electrons (drift velocity) considered to be zero, before setting up any electric field? I mean in the derivation of the equation drift velocity: $$ v =-\frac{Eet}{m} $$
3
votes
0answers
38 views

Partition function of classical quadrupole in an electric field

The partition function of a dipole in an electric field is a well-known problem, analytical solvable (nice integral, can be calculated with pen and paper), for example in the Langevin treatment of ...
1
vote
1answer
54 views

Calculating equipotential lines and current density in a rectangular conductor

(This isn't homework, I'm trying to make an illustration for an article I'm writing.) Let's say that I have a thin rectangular bar of uniform conductivity, and I have point probes at various places: ...
3
votes
1answer
87 views

Are electric field lines due to Faradays law closed?

Are the field lines of electric field produced by Faraday's law of induction (and assuming $\rho = 0$) necessarily closed? If not what would be a counterexample. If it's true, how to prove it in ...
3
votes
4answers
5k views

Why do we test electric fields with positive charges and not negative ones?

Is there any difference between using a positive versus a negative charge to test an electric field?