The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
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4answers
781 views
Do Alkaline batteries, NiMH, rechargeable alkaline, Lithium AA, all have similar MAX POWER?
So in physics, one smart teacher told me,
V = IR
or
I = V / R
but it is not always true, because ...
2
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1answer
1k views
What is the difference between induced and motional emf?
At least from their names, it seems motional emf is induced, so what's the difference?
2
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1answer
113 views
Is it possible create current by spinning a charged sphere?
If we have a sphere which has $σ$ surface charge density and rotate it in axis z will this create current ? Is it possible without any potential difference ?
2
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2answers
293 views
Round bulb and Long bulb in Series Circuit
If you have a series circuit with a battery, one round bulb (with thicker filament), and one long bulb (with thinner filament), the round bulb does not light up and only the long bulb lights up.
...
2
votes
2answers
199 views
Why does the current stay the same in a circuit?
I was informed that in a circuit, the current will stay the same, and this is why the lightbulbs will light up (because in order for the current to stay the same, the drift speed of the electrons need ...
2
votes
2answers
274 views
Higher To Lower Electric Potential
The question I am working on is:
"An electron moving parallel to the x axis has an initial speed of $4.65 \cdot 10^6~m/s$ at the origin. Its speed is reduced to $1.27 \cdot 10^5 ~m/s$ at the point ...
2
votes
2answers
426 views
How can I calculate the wave propagation speed in a copper wire?
First of all: I am a computer science student, so I don't have much knowledge of physics. So please keep your answers simple.
I recently learned something about circuit design and its problems ...
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?
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2answers
2k views
Why does electricity flowing through a copper coil generate a magnetic field?
Can some one please explain to me why electricity flowing though a copper coil generates a magnetic field or where I could possibly find that information? Are there other materials that produce a ...
2
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1answer
525 views
How does a voltage independent current source work?
So I'm having some trouble understanding what a voltage independent current source is. How can you have a current without a voltage. as I understand it voltage or EMF is the force that drives the ...
2
votes
1answer
454 views
How is contact resistivity defined for a Schottky contact, or the Schottky barrier height for an ohmic contact?
Based on the transfer length method (TLM), one can accurately calculate the contact resistivity for an ohmic contact, by evaluating the absolute resistance measured through the test structure and ...
2
votes
2answers
152 views
Introducing emf of a chemical cell as a hint towards quantum mechanics
Today I had a discussion with a colleague who teaches electricity and magnetism to 2nd year undergraduate physics students. He is seeking the best way to explain how is the emf generated inside a ...
2
votes
2answers
530 views
Electric potential in a capacitor
Im a writing a school report regarding the electric energy and potential of a capacitor.
In short:
An experiment was carried out where we charged a capacitor, and then decharged it with an electric ...
2
votes
1answer
101 views
How Special Relativity causes magnetism
So my physics teacher assigned us an article about how special relativity causes magnetism in a wire with a current, even with the low drift velocities of electrons in a current.
It seemed that the ...
2
votes
2answers
69 views
Static discharge out of 3 volts button battery
I am starting to get interested in static electricity
I have found this which is very cool but I do not know how I can control the output voltage.
...
2
votes
1answer
119 views
Calculating engine starter’s energy use
During a discussion on start-and-stop vehicle technology some bloke began pushing the point that re-starting the car uses stored energy from the battery, which needs to be replenished by increased ...
2
votes
1answer
88 views
Which of these two methods is correct for calculating current?
I recently came across a question, for which I saw two possible methods of finding the solution. I was required to calculate the "current flowing" $I$ when given the voltage $V$, frequency $f$, total ...
2
votes
2answers
562 views
Ohmic and Non-Ohmic devices
Why do some conductors follow Ohm's law and some do not? Isn't there any universal law that can explain the flow of current?
2
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2answers
82 views
Lightning driven electrolysis
Could a lightning bolt be harnessed to perform electrolysis, would a useful amount of hydrogen be produced?
I'm imagining some industrial scale device in the ocean with some hydrogen capture ...
2
votes
1answer
64 views
Is Joule heating only between charged particles?
The Wikipedia page for Joule heating explains
"It is now known that Joule heating is caused by interactions between the moving particles that form the current (usually, but not always, electrons) and ...
2
votes
1answer
80 views
Does recharging a battery at a lower temperature lower its internal resistance?
Does temperature affect the internal resistance of batteries? And does charging a "frozen" battery allow it to charge faster than a warm or room temperature battery?
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 ...
2
votes
4answers
810 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 ...
2
votes
2answers
727 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 ...
2
votes
1answer
224 views
Circuit Simulation
I am making a circuit simulation program, and I am not sure how to simulate the behavior of Diodes.
Take this circuit:
...
2
votes
2answers
267 views
How to measure faster than light electric energy?
According to relativity,nothing can break light barrier.But a recent preprint shows energy transmission of commercial electric power (f=60Hz) is faster than light. (It is not the drift velocity of ...
2
votes
1answer
221 views
Practical physics: where does this current come from?
It's been a while since school and I don't remember the right laws and formulas. So I come here. :)
I've got a power cord extender running from the wall outlet to my washing machine. It's about 3 or ...
2
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0answers
57 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 ...
2
votes
1answer
76 views
What exactly causes an increase in resistivity?
Explain in terms of charge carriers why the resistance of copper is less than that of CuSO4 solution, which is less than that of hydrogen gas
This is the question directly asked for homework, and ...
2
votes
2answers
154 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 ...
2
votes
3answers
210 views
Compute closed line integral of electric field in circuit
I have a circuit where resistor is parallel to capacitor, which is charged with voltage U. How to compute line integral around closed loop to get the result of Kirchhof second law - ...
2
votes
1answer
334 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. ...
2
votes
1answer
379 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 ...
2
votes
2answers
901 views
Total power consumption of electric device
For some electric devices, like a fan or air conditioner, I read about their power consumption in watts on their specification guide.
Does it tell about the power at normal or full speed? or Does the ...
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vote
5answers
291 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?
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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 = ...
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vote
2answers
97 views
Why doesn't a neon sign seem that hot?
I heard that neon signs contain plasma, why aren't they hot?
is it because the electrons and ions do not hit the lamp's wall?
Is it because it is non thermal plasma and electrons and ions are not in ...
1
vote
2answers
170 views
Fundamentality of voltage to current
From Ohm's Law :
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points.
I would like to know if ...
1
vote
1answer
16k views
Laptop self charge cable? [closed]
Ok this is a really silly question, but I was really curious as to why this wouldnt work. I'm just starting my electricity and magnetism course, so I really dont know much about electricity. I know ...
1
vote
2answers
89 views
Simple ohms law on a battery ? Paradox or conceptual error?
Suppose we have a regular pencil battery which supplies DC voltage $V$. Say we take copper wire and connect the ends of the battery to an $R$ ohms resistance.
Then Ohm's law tells use the current in ...
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1answer
998 views
Why connect cells in parallel?
Say there is a circuit with two 1.5V cells, and a 100 ohm resistor.
If you connect two cells in series, then the total emf is 3V. And the current will be 3/100 = 0.03 A. (Using V = IR):
If you have ...
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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 ...
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vote
3answers
149 views
How exactly does a resistance reduce current?
I've heard that resistors are used to decrease current to a particular appliance, such as in the regulator of a fan. However, I've also heard that the total current in a circuit is always the same- in ...
1
vote
2answers
57 views
Starting vehicle on hot days
Why it is easy to start the vehicle on hot day than on cold days?
Since on winter days it is diffcult to start than on hot days I thought it is due to the low temperature which in turn affects the ...
1
vote
3answers
1k views
Is the same amount of electricity used for ceiling and table fans on different speeds?
We use ceiling and table fans in home which are can be set to low or high speeds using regulators. I want to ask that does it uses or consumes same amount of electricity at different speeds? Here, ...
1
vote
1answer
134 views
Store up cheap electricity to use later?
My utility company charges me more for electricity in the summer. Is
there any way I could "save up" non-summer electricity (eg, a giant
battery?) and then use it during the summer, saving myself ...
1
vote
3answers
812 views
use of Mobile phone on Petrol pump
I was trying to find out the cause behind the Explosion at petrol pump due to the Mobile phones but eventually it turns out it is not Radio Frequency which may cause the explosion rather it is totally ...
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vote
2answers
296 views
Calculate power $P=V \times I$
I have an adapter which mentions like this...
Input: 100-240V~1.8A
50-60hZ
So how much power does it really consume?
I just knew ...
1
vote
2answers
1k views
Microwaves vs Gas or Electric Coil heating of a water boiler in a typical household
Wouldn't it be more energy efficient and or safe to use microwaves to heat our home's water boiler instead of using dangerous gas or hot electric coils that could catch other things on fire? I'm kinda ...
1
vote
4answers
10k views
What is the relationship between AC frequency, volts, amps and watts?
In an alternating current, how are frequency, voltage, amperage, and watts related?
For instance, imagining the power as a sine wave, what is amperage if voltage is the amplitude? Is there a better ...
