Tagged Questions
0
votes
1answer
37 views
The potentiality of the electric field
Could you, please, explain me using just words why electric the field is potentially? I know the proof using integral: $A = \int_{12}q\overrightarrow{E}\overrightarrow{dr} = ...
0
votes
0answers
67 views
The electric field inside a uniformly polarized cylinder
Given a uniformly polarized cylinder with some polarization $P\vec{z}$ which has radius $R \gg d$ where $d$ is the height and $R$ is the radius. The cylinder's center is on $\vec{z}$ and it's on the ...
5
votes
3answers
110 views
Horizontal $E$-field for a charged conducting disk
For part of a simulation I am writing, I need to know the electric field emitted from a charged conducting disk. If the disk was laid out in the $x$-$y$ plane, I am interested in the field in that ...
0
votes
0answers
36 views
Work required to pull capacitor plates apart when connected to battery [closed]
For (a), I just use $F = k \frac{Q_1 Q_2}{r^2}$, then (b) $W = - \Delta U = - qE \Delta d$, correct so far? But how do I do (c)?
0
votes
0answers
30 views
Energy content after moving point charge [closed]
I have the following exercise:
In point A there is a charge with $Q_1 = 3.3\times10^{-5} C$
In point B charge $Q_2 = 8.5\times10^{-6} C$
In point C charge $Q_3 = -6\times10^{-6} C$
This happens ...
1
vote
1answer
51 views
Maximum separation when 2 unlike charges shot apart
I want to compute the maximum separation when 2 unlike charges are shot apart from each other
...
0
votes
1answer
91 views
Electric field around charged cylinder
This is a homework question, so please don't give me the answer outright. I just need help conceptually.
"A cylindrical shell of length 190 m and radius 4 cm carries a uniform surface charge density ...
1
vote
0answers
40 views
Static electrical attraction [closed]
Coulomb's law is used to calculate the electrical attraction between 2 charged particles, what formula do I use to calculate an electrical attraction magnitude between 2 plates? Let's assume the first ...
0
votes
1answer
53 views
Electric field and potential [closed]
An oil drop of radius 0.70mm containing a charge of -4.8 x 10-19 C is placed in an electric field if the drop remain stationary at the point find the magnitude and direction of electric field ...
1
vote
2answers
134 views
Energy of particle in electric field
I'm taking a physics class and the professor teaches us really basic things in lecture and then gives homework way beyond what he taught in lecture. Obviously I need to find some resource other than ...
0
votes
1answer
109 views
Does the electric field inside a sphere change if point charge isn't in center?
As i understood , if you have a point charge in the center of a hollow conducting sphere then the electric field inside it, is zero because the charge distribution is spherically symmetric.
But ...
0
votes
1answer
227 views
Non conducting charged planes
I have two parallel non conducting charged planes with opposite charges $6\mu C/m^2$, area $A = 3m^2$ and distance between the planes $d = 0.004 m$. I know the potential between these two planes is ...
-1
votes
1answer
233 views
What's the electric field with a point charge not in the center of the sphere? [closed]
That's a hollow conducting sphere link
My charge is at P (10uC). R = 0.15m. PS = 0.05m. DS = 0.35m. What's the electric field at point D?
0
votes
0answers
18 views
Electric field outside nonconducting sphere [duplicate]
An electric charge $Q$ is distributed through out a nonconducting sphere of radius $r_ 0$ and has a spherical cavity of radius $r_1$ centered at the sphere's centre. Assume the charge $Q$ is ...
0
votes
1answer
206 views
Electric field due to nonconducting sphere
For calculating electric field outside a nonconducting sphere with a hollow spherical cavity. When I use the rule (Charge density= $dQ/dV$), I don't know exactly what is $dV$, is the volume here ...
0
votes
0answers
35 views
Charges and Fields [closed]
Three charged particles lie along the x axis of a Cartesian coordinate system. q1 is located at x = 0,
q2 lies at x and q3 lies at x = r. All three charges are positive, but only q2 is free to move. ...
1
vote
1answer
235 views
Electric field strength between 2 positive charges [closed]
I'm having a lot of trouble trying to solve this problem:
Three identical point charges of magnitude $+1.0$ $mC$ are located at the corners of a square that is $1.0$ $m$ on a side. A point charge of ...
1
vote
1answer
124 views
Finding the Electric Field (and other information, besides)
The problem I am working on is:
Two parallel plates having charges of equal magnitude but opposite sign are separated by 29.0 cm. Each plate has a surface charge density of 33.0 nC/m2. A proton is ...
0
votes
1answer
144 views
Finding the electric field
The charge per unit length on a long, straight filament is -91.9 µC/m.
(a) Find the electric field 10.0 cm from the filament, where distances are measured perpendicular to the length of the ...
0
votes
0answers
101 views
Having a hard time answering this electric field question [closed]
What is the electric field at a point when the force on a 1.45uC charge placed at that point is F=(3.0i-3.9j) * 10 ^-3N? Need to find a and B. Sorry I am new to this and do not know how to use the ...
0
votes
1answer
53 views
Help for density of charges in electric field [closed]
This is for a homework assignment so it would be great to have a hint or an explanation of how to do it. In a certain region in space, the electric field is given by
$\vec{E}(r) = \dfrac{A}{r} ...
0
votes
1answer
191 views
Electric Fields
The problem I am working on is, "In the figure below, determine the point (other than infinity) at which the electric field is zero. (Let $q_1 = -2.45\ \mu C$ and $q_2 = 6.5\ \mu C$)
Here is a little ...
3
votes
1answer
368 views
Electric Field due to a charged sphere
Suppose we have a spherical surface with a surface charge density varying as $cos(\theta)$. Apparently one can find the electric field both outside and inside such a spherical surface by superposing ...
1
vote
1answer
293 views
Electric force in DNA molecule
Given that distance between O-H and N-H bonds are 0.11 nm and
How do I compute the net force exerted from Thymine and Adenine? A hint given is:
Hint: To keep calculations fairly simple, yet ...
0
votes
1answer
374 views
How to draw electric fields correctly?
Draw a negatively charged plate A and a positively charged plate B with an equal charge. Draw the field. (the image is the given answer)
I however do not understand why this is. Is there any reason ...
1
vote
1answer
291 views
Finding the electric field for a shell of charge
Suppose we have charge density defined
$$
\rho(x,y,z) =
\begin{cases}
0 & 0 \leq r < a \\
K & a \leq r\leq b\\
0 & b< r
\end{cases}
$$
For some constants $K,a,b$
How would ...
1
vote
1answer
423 views
The formula of the force exerted on an electric dipole by non-uniform electric field
When an electric dipole of moment $\mathbf{P}$ is located in a non-uniform electric field $\mathbf{E}$, there is an net force exerted on it.
However, the formula of the force in some books is read ...
0
votes
2answers
1k views
Why is electric field zero inside a hollow metal sphere ?
The figure below shows a hollow metal sphere with a positive point charge $Q$ sitting outside it. What is the electric field at the center of sphere ? The answer is zero (look at here at the beginning ...
2
votes
2answers
147 views
Energy in electric field
I'm having some trouble understanding a homework question and would appreciate some help.
The question is as follows:
Jenny charges a capacitor with the help of a battery. She then removes
the ...
2
votes
2answers
788 views
Where does the equation $E_q = \frac{kq}{r^2}$ come from in this problem?
A point charge is placed at each corner of a square with side length
$a$. The charges all have the same magnitude $q$. Two of the charges
are positive and two are negative, as shown in the ...
2
votes
2answers
561 views
Electric potential of sphere
(a) I am a little confused about this part. The point at A to B isn't radial. The electric field is radially outward, but if I look at the integral
$$\int_{a}^{b}\mathbf{E}\cdot d\mathbf{s} = ...
3
votes
3answers
1k views
0
votes
0answers
91 views
How can find the electric field at the center of a semicircle (insulation material)? [closed]
I have a thin wand of insulating material. The wand is bent so as to form a semicircle of radius $R=20 cm$. The wand is a uniformly distributed charge $q= 5\ 10^{-9} C$. Calculate the electric field ...
0
votes
2answers
3k views
Using Gauss's Law to calculate electric fields between plates
I have two earthed metal plates, separated by a distance $d$ with a plane of charge density $\sigma$ placed a distance $a$ from the lower plate. I want to derive expressions for the strength of the ...
0
votes
0answers
178 views
Calculating the number of turns and thickness of an electromagnet
I want to calculate the number of turns of an electromagnet and the thickness of the wire.
But i have tried to search arround in books, and can't really find any thing.
I know my wire is 0,114mm and ...
0
votes
0answers
459 views
Rotating Disc and Magnetic Field [closed]
I'm studying for exams, and I am curious as to how the rotation of a disc would affect the magnetic field. The following problem stumps me:
A plastic disc of radius $R$ has a charge $q$ uniformly ...
4
votes
3answers
960 views
“Find the net force the southern hemisphere of a uniformly charged sphere exerts on the northern hemisphere”
This is Griffiths, Introduction to Electrodynamics, 2.43, if you have the book.
The problem states Find the net force that the southern hemisphere of a uniformly charged sphere exerts on the ...
5
votes
3answers
813 views
Charge Distribution on a Parallel Plate Capacitor
If a parallel plate capacitor is formed by placing two infinite grounded conducting sheets, one at potential $V_1$ and another at $V_2$, a distance $d$ away from each other, then the charge on either ...
0
votes
1answer
456 views
Where will the electric field be zero in dipole [closed]
Lets say we have an electric dipole. I can't figure out where the location of net zero electric field will be.
Tnx
1
vote
1answer
270 views
Electric Flux Density - Ring Charge
A ring placed along $y^{2}$ + $z^{2}$ = 4, x = 0 carries a uniform charge of 5 $\mu$C/m. Find D at P(3,0,0)
Should I be using Gauss's Law to solve this problem? I was considering using a spherical ...
3
votes
1answer
916 views
Force from point charge on perfect dipole
Have a point charge and a perfect dipole $\vec{p}$ a distance $r$ away. Angle between $\vec{p}$ and $\hat{r}$ is $\theta$. Want to find force on dipole.
I'm having more than a little difficulty ...
0
votes
2answers
372 views
Help me find electric field strength vector for this given equipotential line
I'm a physics tutor. This is the question from a High school book.
The equation of an equipotential line in an electric field is y = 2x,
then the electric field strength vector at (1, 2) may be ...
3
votes
1answer
343 views
Given charge distribution find electric field
Given a charge distribution $\rho(\vec{r})$ where $\vec{r}$ is the position vector and that $\rho$ is a function of only $|x|$, Why is it that the corresponding electric field $E$ is necessarily of ...
-2
votes
1answer
4k views
Electric field due to nonconducting plastic sheets [closed]
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 (the four surfaces are in the ...
0
votes
2answers
605 views
Electric field problem
First of all I hope I'm doing the right thing by posting this message on the stack exchange site. I know you aren't my personal problem solvers, but I just can't solve it. And maybe this problem is ...
2
votes
2answers
313 views
Gauss' law giving zero field where field is not zero?
Two plastic sheets with charged densities as shown:
I'm trying to find the field at $B$. I obtained the correct answer by adding up the fields created by each charge density. But I realized that ...
2
votes
3answers
2k views
why do we test electric fields with positive charges? not negative ones?
Is there any difference between using a positive vs a negative charge to test an electric field? If so, please explain.
0
votes
0answers
326 views
A question related to Gauss's Law [closed]
I'm unable to solve this numerical based on Gauss's Law:
A charge Q is distributed uniformly within the material of a hollow sphere of inner and outer radii: r1 and r2. Find the electric field at a ...
