Tagged Questions
1
vote
1answer
22 views
Speakers and Static from Hands
Why is it that when you touch the a bare male end of a speaker feed that the speaker makes hissing noises? Is it just (eddy?) currents running through you?
0
votes
2answers
42 views
Do black holes have charges?
Do black holes have charges? If so, how would they be measured? Also, does electricity behave the same way? Black holes affect photons, which are carriers of EM radiation, so do black holes have any ...
0
votes
1answer
43 views
What types of materials can be electrically charged by rubbing?
What types of materials can be electrically charged by rubbing? Is there a certain type of materials in which static electricity can be produced by rubbing together two different materials?
0
votes
2answers
76 views
Definition of electric charge and proper explanation
Is there a definition of electric charge and proper explanation of it?
It is said "Electric charge is the physical property of matter that causes it to experience a force when close to other ...
0
votes
0answers
46 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 ...
3
votes
0answers
39 views
Nature of electricity [duplicate]
Suppose a lightning strikes and there is an iron rod and a coconut tree. How does the electricity know that rod is the least resistant path before hand.
0
votes
2answers
60 views
Why isn't this capacitor charging?
Let's say you have a parallel plate capacitor and you connect one plate to the positive terminal of a battery and the other plate to the negative end. So this is like a static situation, you have a ...
1
vote
1answer
66 views
Can someone explain this intuitively please?
In a static situation we defined voltage as energy/unit charge, or j/c. As the distance between the charged particles increased, the voltage decreased. Now why do we not apply this in a simple DC ...
3
votes
2answers
75 views
What happens to this potential energy?
Let's say I turn on a Van de Graaff which creates a large positive charge. Now let's say I have an object with a positive charge in my hand and I start walking toward the Van de Graaff from $x$ meters ...
1
vote
2answers
221 views
Electric potential at a point outside a charged sphere
The question asked me to find the potential at a distance $r$ from the center of a charged sphere, where $r>r_0$ of the sphere.
Actually, the question is answered, but what is confusing me is ...
1
vote
1answer
114 views
The field of uniformly charged ball (without Gauss theorem)
The solution of Poisson equation is given by
$$
\mathbf E = \int \frac{\rho (\mathbf r )(\mathbf r_{0} - \mathbf r )}{|\mathbf r_{0} - \mathbf r|^{3}}d^{3}\mathbf r.
$$
I tried to use this term for a ...
6
votes
2answers
193 views
Ionized Depletion Region, Why aren't those charged being excited?
Ok so I understand the PN junction, and how when 2 Semiconductor materials are placed together the Electrons will jump into the Holes near the junction creating a Negatively Ionized Atoms on the ...
2
votes
1answer
128 views
Do plastic shoes electrically insulate people from the ground?
I've read on the Internet that wearing plastic shoes doesn't allow electric charges we collect from our environment (PC, TV, appliances) to be earthed.
Is this reasoning correct?
0
votes
1answer
79 views
The Ultimate Hand Dryer
I have come across many hand dryers that attempt to dry your hands really fast after you wash them. Here are two of them:
XLERATOR
http://www.exceldryer.com/
Dyson Airblade
...
1
vote
2answers
332 views
How do electrons repel?
I understand the basics, protons have a positive charge, neutrons have no charge, and the electron has a negative charge. But looking at the lines of force from a proton, they flow outward and push ...
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 ...
11
votes
2answers
2k views
Why do grapes in a microwave produce plasma?
Some of you may know this experience (Grape + Microwave = Plasma video link):
take a grape that you almost split in two parts, letting just a tiny piece of skin making a link between each half-part.
...
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 ...
0
votes
3answers
461 views
When I connect two charged capacitors side by side, what will be the voltage across them?
Say, I have two charged capacitors, one 3mF and one 2mF. The voltage across them are 20V and 30V respectively. Now if I connect the two capacitors side by side as shown below, what will be the voltage ...
0
votes
1answer
175 views
Faraday's law and superconductivity
According to Faraday's law of induction, volts = -Number of coils in a solenoid * change in strength of magnet / change in time. This doesn't take into account distance or speed, only time. If amps = ...
0
votes
4answers
1k views
If something has zero resistance, does it have infinite amperage?
If amps = volts / ohms, and ohms is 0, then what is x volts / 0 ohms?
1
vote
2answers
309 views
Simulator for electrostatics
I am searching for a tool that visualizes the electric field/potential for simple electrostatic configurations like
conducting/polarized sphere in an uniform electric field
conducting/polarized ...
1
vote
1answer
143 views
Residual Resistivity in alloys and metals
Residual Resistivity
I saw that the graph of resistivity to temperature of alloys like nichrome is like so
Meaning that even at 0 K it has some resistivity just like copper :
I read some where ...
0
votes
1answer
195 views
Equipotential Contour mapping and making it 3D [closed]
I have seen Contour diagrams for Equipotentials . That are drawn like so:
I also saw One image for these contours that was in 3D (Negative Point Charge) :
I was Wondering If there's any ...
1
vote
1answer
678 views
When the electric field in an electrostatic charged conductor is zero, is the potential within also zero?
Let's say you have a point charge inside a conducting shell with an inner radius of 5cm and an outer radius of $7cm$. The point charge has a chard of $-4C$ and the shell a charge of $6C$. This means ...
3
votes
1answer
177 views
Why does hair stand up when standing under power lines?
My initial guess would be the immense electric field around the lines, that causes hair to get charged and due to each hair having the same charge they start to repel each other.
So what is exactly ...
2
votes
2answers
138 views
Differences In Potential Equations
Could someone please describe the differences between the uses each of these potential equations:
Potential due to a point charge:
$V = \frac{k \cdot q}{r} - \frac{k \cdot ...
0
votes
1answer
873 views
As ISA Practical - Resistors in Parallel [duplicate]
Possible Duplicate:
Current against the inverse of resistance graph, I = V/R +c
How would you set up a circuit with a fixed resistor in parallel with a variable one. We are told to measure ...
2
votes
1answer
364 views
Electrical flow in a simple parallel circuit
I'm having trouble understanding something in one of my text books:
Let’s have a look at the implications of each circuit configuration.
Figure 3.13 shows the Conventional representation of a ...
2
votes
5answers
1k views
How can I prevent being zapped by static electricity every time I touch a doorknob or handle in the office?
I don't know what it is about this office, but it seems everything I touch (doorknob, bathroom faucet, edge of kitchen sink in the break room), I get zapped by static electricity. It's getting old. ...
3
votes
1answer
808 views
How can a conductor be grounded yet there are induced charges on it?
A classic example for the method of images is the following, quoted from Griffiths's Introduction to Electrodynamics, page 121:
"Suppose a point charge $q$ is held a distance $d$ above an infinite ...
2
votes
1answer
381 views
Electrostatics:Basic question on electric current
I've got two questions for you.
Electric current is the flow of electrons across a conductor.Why has it always got to do with electrons and not with protons? (I know neutrons are not eligible for ...
4
votes
2answers
296 views
Algorithm of Lightning Strikes?
Given an array of charge for a given area (2D or 3D), what algorithm would describe the path that lightning takes?
An example algorithm would be from the highest charge of the cloud, find the lowest ...
0
votes
2answers
5k views
Determine the point at which the electric field is equal to zero?
Two point charges, -2.5 micro coulombs and 6 micro coulombs, are separated by a distance of 1m (with the -2.5 charge on the left and 6 on the right).
What is the point where the electric field is ...
4
votes
1answer
310 views
Balloon rubbing; where do the electrons go?
If you rubbed a balloon with a towel, where would the electrons go: the balloon or the towel? Why?
I'm guessing the electrons would go to the object with a larger mass, but it's just a guess. :)
-1
votes
4answers
978 views
Resistance between two points on a conducting surface
Suppose we have a cylindrical resistor, with resistance given by $R=\rho\cdot l/(\pi r^2)$
Let $d$ be the distance between two points in the interior of the resistor and let $r\gg d\gg l$.
Ie. it is ...
