The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
7
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2answers
146 views
What could magnetic monopoles do that electrically charged particles can't?
I understand the significance to physics, but what can a magnetic monopole be used for assuming we could free them from spin ice and put them to work? What would be a magnetic version of electricity?
...
2
votes
2answers
215 views
Using Electrostatic Force to Repel Dust From an Object
I have two 4,000V, 2.5mA, DC power supplies and am attempting to use them in such a way to cause a 6x4x1-inch ABS plastic object to repel dust from the ambient air and prevent this dust from settling ...
1
vote
2answers
136 views
What is a “gravitational cell”?
I am not a physicist, and I don't understand the details of electromagnetism. Anyhow, I was looking for how the batteries work in Google. So, I came across this article: "How batteries work: A ...
6
votes
1answer
223 views
Relativistic drift velocity of electrons in a superconductor?
Is there a formula for the effective speed of electron currents inside superconductors?
The formula for normal conductors is:
$$ V = \frac{I}{nAq}$$
I wonder if there are any changes to this ...
4
votes
1answer
166 views
Impurity scattering temperature dependence
Is there any temperature dependence of relaxation time in impurity scattering of conducting electrons? It seems to me that there is none. But, some people claim that there is.
So if you could ...
1
vote
1answer
35 views
Why does a moving electric charge have nonuniform electric field lines?
The electric field of a stationary electron is uniform, radially symmetric with straight field lines. However, the electric field of a moving electron still has radial and straight field lines, but ...
1
vote
1answer
106 views
Am I properly identifying the resistor terminal voltage?
The frequency applied to a circuit of voltage 120 V with a real coil and a resistor has a value of 50 Hz. The resistance of the resistor is 10 $\Omega$. The voltage at the resistor terminals ...
1
vote
1answer
370 views
Can energy be extracted from clouds?
Can cloud charge imbalance be used as an energy source?
First off quite some energy must be present in clouds: a lightning path is quite long, and electrical breakdown of air requires about 1MV/m. ...
0
votes
1answer
21 views
Lightning and Charge Displacement
There is something I don't really understand about flashes of lightning.
When a flash occurs, how come electricity be transferred at the speed of light since electricity's displacement is very slow ?
...
0
votes
1answer
62 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 ...
0
votes
1answer
86 views
If we connect a block of p-type semiconductor only to a positive terminal, will it become positively charged?
Connect the positive terminal of a battery to a piece of p-doped semiconductor, say, silicon doped with boron. Will the terminal pull electrons out of the doped silicon, or equivalently, inject holes ...
2
votes
0answers
59 views
Current between supeconducting rings
How to calculate the current between two superconducting rings with radius r separated by a distance d?
Please note that being unfamiliar to the concept of superconducting rings, I can't approach ...
1
vote
0answers
27 views
How to size an electromagnet
How can I size an electromagnet? For example if I would to attract a mass of $x$ kg what are the calculations that I must do to size the ferromagnetic core and of course the solenoid? And thus, how ...
1
vote
0answers
69 views
How does current flow in a irregularly shaped heterogeneous resistor?
The motivation for my question is understanding how electricity gets through your skin as opposed to running along it, and how the presence of things like water on the skin affect the relative ...
1
vote
0answers
38 views
Contact electricity and photoelectric effect
Most universities provide an experiment about the photoelectric effect to determine $h$ by measuring the stop voltage against the light frequency and calculating the slope $h/e$.
But mostly they also ...
1
vote
0answers
12 views
Early Concepts in Relation with the Forces Produced When Certain Pairs of Objects are Rubbed Together
It was found centuries ago that these materials: wool cloth and paraffin wax, glass rod and silk cloth when rubbed against each other attracted one another. While two glass rods when rubbed against ...
1
vote
0answers
29 views
pressure required for displacing a single electron off a crystal
I need to know this for my project- "power generation using the pressure applied on a keypad of a mobile electronic device". How much pressure does it take to displace a single electron off its ...
1
vote
0answers
29 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 ...
1
vote
0answers
57 views
Why do power lines buzz more when it is low-humidity outside?
I have observed that the power lines buzz louder when there is less moisture in the air.
Why is this?
If it will help the lines are located on the foot hills of a nearby mountain.
1
vote
0answers
96 views
Braess's Paradox in Electrical Circuits
According to this and other similar papers, http://www.nature.com/nature/journal/v352/n6337/abs/352699a0.html, adding a current-carrying path can increase the voltage drop across a circuit. What is ...
1
vote
0answers
722 views
Question on Shockley's diode equation
We owe a debt to Bell labs with Shockley, Bardeen and Brattain for inventing the semiconductor.
All have now passed on. I remember seeing my first transistor radio in the early 60's.
Shockley ...
1
vote
0answers
271 views
What is a boundary condition for capacitors/dielectrics?
I am extremely confused about what boundary conditions are. One minute ago I was solving easy capacitor questions and the next minute I am being asked boundary condition questions and there is no such ...
1
vote
0answers
79 views
Is it possible to transform chemical energy in electrical energy by modifying the equilibrium constant?
Considering a Daniell cell, is it possible to create endlessly electrical energy by using atmospheric temperature (for exemple) variations to modify the reaction's eqilibrium constant ? I apologize if ...
1
vote
0answers
105 views
Schottky and shot noise
I am looking for a little history on shot noise: when was it first predicted and first measured?
In particular, what was the role of Schottky? His 1918 paper "Über spontane Stromschwankungen in ...
1
vote
0answers
241 views
what happens if i charge a a Li-ion battery with non nominal voltage?
Suppose that i have a li-ion battery with voltage 10V (and some capacity, say 1000mAh).
Can i charge it completely using 5V voltage?
What will hapen if i charge it with 12V voltage?
edit:
Found ...
0
votes
0answers
24 views
Does passing large amount of current(via large potential difference) for a large amount of time decrease resistance
So, I just learnt that by developing potential between two points of a conducting wire, the electrons rush towards the point with high potential due to the electric field generated by it. Also that ...
0
votes
0answers
19 views
Need an intermediate resistivity part/material
I need a part or material for a planned experiment (the experiment is similar to those described in my articles http://arxiv.org/abs/1208.0066 and http://arxiv.org/abs/1109.1626 ). The problem is that ...
0
votes
0answers
15 views
Charging by induction (and grounding)?
The very familiar phenomenon of charging by induction includes bringing a charged object near an uncharged sphere to induce a separation of charges in it and then grounding the charge (same as the ...
0
votes
0answers
25 views
Electrical properties of molten gallium arsenide
I'm looking for the resistivity and magnetic permeability of molten gallium arsenide, but can only seem to find the values for the solid material at room temperature (e.g., Wikpedia). Not even ...
0
votes
0answers
29 views
About electric current analogy
my teacher gave me this analogy to the electric current , the wire is like a pearl necklace where the pearls can move, the current or the movement of electrons is like putting your fingers between 2 ...
0
votes
0answers
44 views
Object accelerated by electromagnet
If I have an electromagnet (powered by a battery) and a metallic object, the
power generated will depend on the voltage of the battery and the resistance of the coil.
If I accelerate the object, will ...
0
votes
0answers
56 views
Why it happen's when I rub my finger's?
I have a pc with a metallic body on my CPU case. Yesterday suddenly the earthing wire of my CPU broke down and I was able to feel a little bit current on touching it's metallic body. But what I found ...
0
votes
0answers
33 views
Why $Q_{f}$ on glass ~ $12Q_f$ on air in Leyden Jar Expt?
I watching a video lecture on the internet and at at about 46:55 the professor says that the free charge ($Q_f$) on the glass is about 12 times that of air in an experiment with a Leyden Jar. He says ...
0
votes
0answers
67 views
Quantization in room temperature
I can't understand
Why is quantized conductance in this scheme ?
http://postimage.org/image/4nujpfe7j/
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votes
0answers
171 views
fringing field capacitance
I am having two doubts about the fringing field capacitance.
1) In most of the formulae, the fringing correction for the capacitance is written per unit length. This is ok if the length is very ...
0
votes
0answers
49 views
Piezoelectrical effect in a pendulum
How can I compute the piezo-electrical effect of a pendulum of frequency $f$ and amplitude $R$? What constants of the material will enter the computation?
The material in question is an electrode on ...
