The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
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1answer
179 views
Tubelights+power lines pictures?
I've come across many pictures like these, sometimes in chain emails reporting the dangers of power lines.
Another claim is that they run on "wasted" energy.
The explanations given are that the ...
9
votes
3answers
304 views
Current in a simple circuit
I was going over my notes for an introductory course to electricity and magnetism and was intrigued by something I don't have an answer to. I remember my professor mentioning, to the best I can ...
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0answers
50 views
How can I figure out how many kWh's are in a battery using the mAh's and voltage. [duplicate]
Possible Duplicate:
Relating milliampere-hours to watt-hours for batteries
How can I figure out how many kWh's are in a battery using the mAh's and voltage.
Some batteries only list mAh's ...
1
vote
1answer
345 views
How do home-made capacitator bottles affect a tesla coil?
In the tutorial I'm following, the guy uses 6 snapple bottles to make capaciter (by covering them with foil and filling them with salt water) for a 9kV 30mA input. I have a stronger transformer (15kV ...
2
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1answer
162 views
Asynchronous generator run in vacuum chamber
what will be happen if we put asynchronous generator in vacuum chamber & run it above its synchronous speed. After reaching its over synchronous speed we will cut off electrical supply. Can it run ...
1
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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
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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 ...
2
votes
3answers
1k views
How much energy was consumed when we turn on/off light?
My parents told me to turn off the light when I am not using it. But I remember my physics teacher told me that the action of turning on/off a light can cause huge energy. I am wondering how much is ...
0
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1answer
186 views
Magnetic Susceptibility- Permeability
What is the permeability of magnesium sulphate and therefore the magnetic susceptibility?
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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 ...
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3answers
163 views
Lightning Power?
What is the power source of a lightning? It doesn't consume fuel, nor an atomic fission/fusion, but it discharges a large amount of energy. Is it feasible to create an artificial lightning using the ...
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2answers
334 views
How can I measure the conductivity of a copper rod?
I would like to perform an experiment to measure the conductivity of a copper rod. What device can I use to perform to experiment? is there such a thing as a conductivity meter? All i found was an ...
2
votes
1answer
339 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. ...
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vote
5answers
292 views
How do electrical devices suck electricity?
If the electric potential is 220V and some device needs 1500watts then how does it suck exactly that amount of electrical energy from outlet?
4
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1answer
111 views
How can there be a path to ground with thick shoes and a carpet?
I'm connecting a test light to one pin of an halogen lamp. When I touch the metallic part on the back of the test light, the light glows, as it is supposed to. However, I have thick shoes and I am ...
2
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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 ...
5
votes
2answers
1k views
how calculate resistance between two points for arbitrary resistor grid?
I need to calculate resistance in an electrical grid.
Grid is a graph. Edges of a graph are resistors. How calculate resistance between any two vertexes for arbitrary graph?
I know Kirchoff law and ...
2
votes
4answers
2k views
Understanding the relationship between electricity and magnetism
I keep on hearing that magnetism is just another form of electricity and vice versa. If that's the case why can't we use magnets as batteries, and why aren't my batteries magnetic?
3
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2answers
544 views
Relating milliampere-hours to watt-hours for batteries
I've seen many batteries that are measured in milliampere hours (mAh), while others are measured in watt hours (wh). How can I convert them between each other so that I can actually compare them? It's ...
1
vote
1answer
4k views
How much energy is in a lightning strike?
According to Wikipedia an average lightning has 1TW, the whole world used 16TW in 2006. (I suppose this means the same as 16TWh in one year?) Sometimes the lightning reaches 100kA. This peak last for ...
4
votes
2answers
326 views
Why do physicists believe protons and electrons are present in equal numbers?
I tended to consider that negative and positive charges are present in equal numbers in the universe to be a known, obvious fact. But is it so? How can we rule out the possibility that there is some ...
0
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1answer
234 views
polyphase circuits
I was going through a physics book which contains a short description of Nikola Tesla . The description mentioned about poly phase circuits (power supply). Out of curiosity I googled it up and I found ...
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2answers
978 views
Internal resistance V=IR circuit question [closed]
I don't know how to resolve this problem.
A complete circuit consists of a 18,0 V battery (internal resistance r) and a resistor R. The terminal voltage of the circuit is 15,8 V and the current is ...
2
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5answers
437 views
Why doesn't an electron accelerate in a circuit?
Why don't electrons accelerate when a voltage is applied between two points in in a circuit? All the textbooks I've referred conveyed the meaning that when an electron traveled from negative potential ...
0
votes
3answers
426 views
How can AC source with different voltage provide same power
As some of us maybe aware, USA mains connection is 110 V while those in Asian countries are 220 V. How is it still possible for the Adapter to provide the necessary power to the device, say a laptop, ...
2
votes
2answers
1k views
How do I join two co-axial cables?
I'm trying to join two ends of co-axial cables. I've managed to connect the two ends of copper wires but still the signal response is very low. When I try to stretch the cable signal gets good. Why ...
1
vote
1answer
377 views
What is the capacitance of a superconductor?
I heard somewhere that the capacitance of a superconductor is much higher than regular conductors, but I haven't heard or seen anything yet proving or disproving such. So whats the truth? And why?
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4answers
622 views
Effects of a Coiled Cable
Okay, I've got a little bit of a layman's question here.
We're doing a bit of spring cleaning in our office and we've found a cabinet with boxes upon boxes of stored wires, so naturally, this ...
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vote
1answer
445 views
How can a portable 5V battery charge another 5V battery?
For a device that is portable and can charge an iPhone 4 or Nintendo 3DS:
http://www.amazon.com/New-Trent-iCruiser-IMP1000-Blackberry/dp/B003ZBZ64Q
I wonder, if this device outputs 5V, and iPhone or ...
0
votes
1answer
196 views
Equation for finding electrical resistance
I want to know how the flow of electrons will change when I change the tempertature from 100 F to 250 F in a silicon semi-conductor (ex: computer mouse)
How can I find this out?
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vote
1answer
2k views
Current against the inverse of resistance graph, $I = V/R +c$
If I have a plot of current ($y$ axis) against 1/Resistance ($x$ axis).
The circuit it is measured from is a simply 2 resistors connected in parallel to battery, where the potential across the ...
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. ...
4
votes
5answers
485 views
Why are $\mu_0$ and $\epsilon_0$, which appear in electrostatics and magnetostatics, related to the speed of light which appears in electrodynamics?
$\epsilon_0$ and $\mu_0$ appear in electrostatics and magnetostatics. When we include time varying fields we have electrodynamics and the appearance of c which turns out to be related to $\epsilon_0$ ...
4
votes
2answers
2k views
What happens to a fully charged battery, when you continue to charge it?
If i leave my cell-phone charging the whole night, it will be fully charged after a while. What happens with the battery and the excess energy I add? Also, I noticed my charger emitting a different ...
11
votes
4answers
2k views
Why is the charge naming convention wrong?
I recently came to know about the Conventional Current vs. Electron Flow issue.
Doing some search I found that the reason for this is that Benjamin Franklin made a mistake when naming positive and ...
3
votes
1answer
323 views
Is there something like the Poynting vector for hydraulic circuits?
The Poynting vector is a representation of the energy flux in electromagnetics, showing the amount and direction of power flow at different points in space. In electric circuits, the energy is not ...
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2answers
334 views
Does power from a resistor perform work or heat transfer?
Let's say I have a cylindrical piston filled with air and fitted with an electrical resistor. The resistor has a current going across it and a voltage for a certain amount of time. My system would be ...
2
votes
4answers
813 views
Total Resistance of Infinite Resistor Grid?
The problem of the infinite resistor grid is very common. The solution for the resistance between any 2 nodes in an infinite resistor lattice is all over the internet.
My question is somewhat similar ...
7
votes
2answers
473 views
Desperately Need Help with Grade 9 Static Electricity
I am preparing to teach Grade 9 Static Electricity next week and am going crazy trying to figure out what is happening in one of my experiments. I have a short piece of PVC pipe, 4 inches diameter, ...
2
votes
2answers
731 views
Voltage and Current in transformers
In transformers, the ratio of the voltages equals the ratio of the turns - so double the output coil's turns and the output voltage doubles. Then, in order to conserve energy, current halves.
This ...
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vote
2answers
762 views
Measuring the Electromotive Force and Internal Resistance of a Battery?
Here is a problem that emerged some time ago:
We needed to measure the emf(electromotive force) and internal resistance of a car battery. The only instruments were voltmeter and ammeter.
...
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 ...
4
votes
1answer
90 views
Superconductors and electrical fields
I have been looking around to figure out how superconductors are made. What ways are there to create a superconductor that don't involve a coolant like liquid nitrogen? Is it possible to cause a ...
1
vote
3answers
261 views
Problem with an electricity / thermodynamics assignment
I've been trying to figure this one out for a while on my own, so I'd like to ask for your help if you could offer some.
The task states:
A heater made out of a wire with a diameter $R = ...
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 ...
10
votes
1answer
421 views
Explanation for speed of an electrical impulse
Our calculus book, Stewart, has a problem where they claim that for a metal cable (inner radius $r$) encased in insulation (outer radius $R$), the speed of an electrical impulse is given by
$$v = - ...
1
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4answers
3k views
domestic electric AC wiring - Live and Neutral correct or not? [closed]
On electric circuits, with $120$ or $230$ AC mains, there are the wires Live and Neutral.
The wiring isn't symmetrical : following the circuit, you cannot switch $L$ and $N$.
However, in Italy, ...
8
votes
8answers
3k views
What is the difference between electric potential, voltage and electromotive force?
This is a confused part ever since I started learning electricity. What is the difference between voltage and electromotive force (emf)? Both of them have the same SI unit, right? I would appreciate ...
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1answer
734 views
How does the X-Y mode of an oscilloscope work?
I recently used an oscilloscope in X-Y mode to draw the phase ellipsis of two voltages. I then used the formula phi = arcsin(2y/B) where y is the value of the ellipsis at x = 0 and B is the total ...
