Tagged Questions
2
votes
2answers
70 views
Force Between Two Conducting Spheres
Aakash PHYSICS JEE (Main & Advanced) Study Package - 5 & 6 (Class XII)
Chapter - Electric Charges and Field
Assignment (page 12)
SECTION - A; Q.no - 1
...
5
votes
3answers
100 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 ...
1
vote
2answers
72 views
The electric potential and the electric field
I'm preparing for my school exam in physics and I found that I don't understand the derivation of $E = -\nablaφ$. Here is a derivation from my book:
1) Imagine that 1 and 2 are infinitely close ...
0
votes
0answers
22 views
Electrostats and Photoelectric effect [closed]
Here I think ,
one beam will knock out just one electron. So I am not able to even understand what the question says , please someone give a hint as to what the question asks
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
34 views
Sign issue on electrostatic potential energy
I have been working on a problem about finding the electrostatic potential energy stored on a capacitor of concentric spheres with inner radius $a$ and outer radius $b$ and with charge $Q$. I've got ...
0
votes
0answers
44 views
The electrical field of a conductive sphere containing a charge - gounded vs not grounded
Let's suppose we have a sphere but unlike theoretical ones it'll has have some thickness say $\Delta r$ and inner radius $R$. What I was wondering about is how will it behave if we place some charge ...
-2
votes
0answers
80 views
How do you find the total electric potential energy? [closed]
Examine the charge distribution shown in this system (see below). Sphere 1 has a charge of +3.0 × 10-4 C; sphere 2 has a charge of –3.0 × 10-4 C; and sphere 3 has a charge of +3.0 × 10-4 C.
Here is ...
1
vote
1answer
53 views
Induced charge on sphere
I have a conducting sphere ($radius = a$) at potential $V_0$. It is enclosed by another thin shell ($radius = b, b > a$) which has a charge density $\sigma (\theta) = \sigma_0 \cos(\theta)$ for the ...
-1
votes
0answers
45 views
Electric Potential and Electric field intensity [closed]
A hollow charged metal sphere has a radius r . If the potential difference between it's surface and a point at a distance 3r from the center is V, then the electric field intensity at a distance 3r ...
1
vote
0answers
37 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
50 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 ...
0
votes
0answers
121 views
Energy stored in charge capacitor [closed]
Two identical parallel-plate capacitors, each with capacitance $C$, are charged to potential difference $V$ and connected in parallel. Then the plate separation in one of the capacitors is doubled.
...
0
votes
1answer
61 views
Find the dielectric constant of the medium?
Two point charges a distance $d$ apart in free space exert a force of $1.4\times10^{-4}N$. When the free space is replaced by a homogeneous dielectric medium, the force becomes $0.9\times10^{-4}N$. ...
0
votes
1answer
220 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
vote
1answer
149 views
Finding Electric Field outside a Charged Cylinder
I'm trying to solve a problem that involves finding the electric field due to a uniformly cylinder of radius $r$, length $L$ and total charge $Q$. Well, my thought was: if I am to use Gauss' Law, I'll ...
0
votes
1answer
59 views
how to find the diameter of this fuse? [closed]
A fuse blows if the current exceeds 1.0 A. It is made of material that melts at a current density
of 620A/cm2. What is the diameter of the wire, assumed to have a circular profile, in the
fuse?
0
votes
0answers
41 views
Force acting on cube's face [closed]
Let's consider a hollow cube. Its faces are uniformly charged with surface density
of charge = $\sigma$.
Authors of that problem ask to find:
1) Force acting on each face of cube from charge $q$ ...
1
vote
2answers
106 views
How to check units?
I've got: $Q=\frac{Er^2}{k}$
how to check the units?
I start with $\left[\frac{\text V}{\text m} \, \text m^2\right]$, tried replacing $[ \text V ]$ with $\left[ \frac{\text J}{\text C} \right]$, but ...
0
votes
1answer
63 views
Electric charge and the distance
The strength of an electric field is: $E = 200\ \mathrm{N/C}$
The potential (of the test charge) is: $V = 600\ \mathrm{V}$
$\epsilon_r=1$
I need to calculate the distance between this point and the ...
0
votes
1answer
198 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 ...
-1
votes
1answer
202 views
Potential due to a spherical surface charge
The potential at the surface of an insulating sphere (radius R) is given by
$$V(R,\theta) = k \cos(3\theta)$$
where $k$ is a constant. Use separation of variables to find the potential inside the ...
0
votes
0answers
62 views
Finding final charge distribution on capacitors on grounding
I am trying to solve the following problem on capacitors:
Here's the circuit
I have to find the total energy loss when all three switches are closed, and subsequent equilibrium attained.
I had ...
5
votes
3answers
220 views
Force between two charged rods?
Suppose that we have two rods of length $l_1, l_2$ connected at one end but free to rotate. These rods have charge density $\lambda$ uniformly distributed, so the total charge of rod $i$ is $\lambda ...
-1
votes
1answer
73 views
electrical forces of two charges repelling each other
If I place two positive charges of different magnitudes on the x-axis (one at the origin, one at the some position x), as the two charges repel each other are the forces that they impart on each other ...
0
votes
0answers
71 views
Electric potential due to an infinite polarized sheet
I have an infinite plane (no thickness) with a uniform dipole density $\mathbf p = p \mathbf n$, with $\mathbf n$ being the normal to the plane. So the surface charge density is $\sigma = \mathbf p ...
2
votes
3answers
252 views
Maxwell Stress Tensor in the absence of a magnetic field
I'm having some trouble calculating the stress tensor in the case of a static electric field without a magnetic field. Following the derivation on Wikipedia,
Start with Lorentz force:
$$\mathbf{F} = ...
1
vote
1answer
121 views
Finding the electric field on a point (x,y,z) using Coulomb's Law
Using Gauss' Law, the answer is $$\frac{Q}{4 \pi \epsilon R^2}.$$
However if I were to do the integration using Coulomb's Law, I get
$$ \int_0^{2\pi} \int_{0}^{\pi}\int_r^a \frac{\rho \sin\theta dR ...
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
2answers
113 views
Calculate force of electric charges “suspended” by strings
In a question:
Two small plastic balls hang from threads of negligible mass. Each
ball has a mass of 0.110g and a charge of magnitude q. The balls are
attracted to each other, and the ...
0
votes
1answer
187 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
367 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
151 views
Electric field of a flat metal plate and a point particle
I'm currently studying electric potential, and I'm having trouble with one of the problems on my homework:
A) A point particle with charge $+q$ is on the x-axis at a distance $d$ from the origin, ...
1
vote
1answer
261 views
( Legendre Generating Function) Off axis Electric Potential from an insulated disk
An insulated disk, uniform surface charge density $\sigma$, of radius $R$ is laid on the $x,y$ plane. Deduce the electric potential $V(z)$ along the z-axis. Next consider an off axis point $p'$, ...
1
vote
1answer
290 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 ...
2
votes
3answers
276 views
Delta Dirac Charge Density question
I have to write an expression for the charge density $\rho(\vec{r})$ of a point charge $q$ at $\vec{r}^{\prime}$, ensuring that the volume integral equals $q$.
The only place any charge exists is at ...
1
vote
1answer
164 views
What is the energy of interaction between a point charge and an infinite cylinder?
I don't remember enough from my electromagnetism course and I can't find any simple, full example on this subject.
I know, that I can consider the cylinder as a wire with the same charge density ...
3
votes
1answer
543 views
Electric Potential of a Charged Sphere
Problem Consider a sphere with radius $R$, and with a charge distribution $\rho(r)=\rho_0r$. Using Poisson's equation, calculate the electric potential inside and outside the sphere.
Solution I don't ...
3
votes
2answers
572 views
Electric field and electric potential of a point charge in 2D and 1D
in 3D, electric field of a piont charge is inversely proportional to the square of distance while the potential is inversely proportional to distance. We can derive it from Coulomb's law.
however, I ...
1
vote
1answer
411 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 ...
1
vote
2answers
211 views
Find the quantity of charge - given potential function
A potential function is given by $V(r)=\frac{Ae^{-\lambda r}}{r}$ Find charge density and hence charge.
I first took the gradient of potential to get $\vec{E}(r)=\frac{Ae^{-\lambda ...
0
votes
1answer
239 views
Simple quadrupole moment
I have a very simple problem: There is a charge $-q$ at $(0, 0, d)$ and $(0, 0, -d)$ as well a charge $2q$ at $(0, 0, 0)$. I have to calculate the quadrupole moment using spherical coordinates. I use ...
0
votes
0answers
69 views
Subtle problem on capacitors [closed]
Imagine we have 2 capacitors of capacitance $C_1$ and $C_2$ respectively. One is charged with charge $Q_1$, and the other is not charged.
Now we connect them in series as shown in figure:
What is ...
6
votes
0answers
221 views
Capacitance of this unusual capacitor
This capacitor is composed of two half spherical shelled conductors both with radius $r$. There is a very small space between the two parts seeing to that no charge will exchange between them.
...
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 ...
0
votes
2answers
119 views
Task with three metal plates [closed]
There are three parallel metal plates. Two boundary plates are fixed and connected with a galvanic battery, maintained a constant potential difference $\Delta \varphi$. Middle plate was initially in ...
0
votes
1answer
175 views
Capacitance and Light Bulb And Dielectric Slab [closed]
An electric lamp having coil of negligible inductance connected in series with a
capacitor and an AC source is glowing with certain brightness. How does the
brightness of the lamp change on reducing ...
1
vote
0answers
138 views
A square with electric field lines parallel to its sides [closed]
A square ABCD has charges $+q$ and $-q$ on the vertices A and C (diagonally opposite sides). How can I place point charges outside this square so that electric field lines are parallel to all the ...
1
vote
2answers
144 views
Is it really to solve problem below by using, in the main, Gauss law?
There is an infinite cylinder surface which uniformly charged along and has a surface charge density, which can be represented as
$$
\sigma = \sigma_{0}cos(\varphi ),
$$
where $\varphi$ - polar angle ...
