Questions tagged [electricity]
The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
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Why does public mains power use 50-60 Hz and 100-240 V?
Is there a physical reason behind the frequency and voltage in the mains electricity? I do not want to know why exactly a certain value was chosen; I am rather interested to know why that range/order ...
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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 ...
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Does electricity flow on the surface of a wire or in the interior?
I was having a conversation with my father and father-in-law, both of whom are in electric related work, and we came to a point where none of us knew how to proceed. I was under the impression that ...
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Why do grapes in a microwave oven produce plasma?
Some of you may know this experiment (Grape + Microwave oven = 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-...
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Why do power lines buzz?
When near high tension power lines, particularly after a good rain, the lines themselves emit a buzzing noise. A similar noise can be heard coming out of the electric meters attached to my apartment.
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In what order would light bulbs in series light up when you close a long circuit?
For a few days, I was thinking of this question.
Lets assume we have a simple circuit that is 100 meters long. And lets say that we have bulbs A, B and C connected to the circuit's 30th, 60th and ...
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If water is not a good conductor, why are we advised to avoid water near electricity (no wet hands near circuits etc.)?
How can water be a medium to conduct current while its ionisation is so negligible that, in principle, no current should flow?
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Why do we use AC for long distance transmission?
Why do we use AC (Alternating Current) for long distance transmission of electrical power?
I know that AC is such a current that changes polarity (magnitude and direction) and has fixed poles.
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Why don't electric fish shock themselves?
Fish like electric eels and torpedoes have specially designed nerve cells that allow them to discharge hundreds of volts of electricity.
Now, while pure water is usually nonconductive, the dissolved ...
user172
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Why is there no magnetic field around a wire connected to electricity at home?
Is it true that an electric current that flows through a conductor creates a magnetic field around the conductor?
If yes, then why doesn't the magnetic sensor of my mobile device react in any way to ...
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How did physicists know that there are two kind of charges?
Problems
The question I am about to make is either too stupid or hasn't bothered anyone because its obvious because I can't really find the answer anywhere.
I am currently studying electricity and ...
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Why is AC more "dangerous" than DC?
After going through several forums, I became more confused whether it is DC or AC that is more dangerous. In my text book, it is written that the peak value of AC is greater than that of DC, which is ...
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Difference between live and neutral wires
In domestic electrical circuits, there are 3 wires - live, earth and neutral. What is the difference between the live and neutral wires?
As there is AC supply, it means that there are no fixed ...
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Why do electric sparks appear blue/purple?
Electric sparks tend to appear blue or purple or white in color. Why?
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Does alternating current (AC) require a complete circuit?
This popular question about "whether an AC circuit with one end grounded to Earth and the other end grounded to Mars would work (ignoring resistance/inductance of the wire)" was recently asked on the ...
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Why can electric cars recoup energy from braking, but a spaceship cannot?
It is said that in a spaceship, you need to spend as much energy to brake as you spent for accelerating. An electric car, however, charges its batteries while braking, thus it actually recovers energy ...
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Wind generators - why so few blades?
Why commercial wind generators usually have just 2-3 blades?
Having more blades would allow to increase power OR decrease diameter.
Decreased diameter would also reduce stress due to different wind ...
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Speed of light vs speed of electricity
If I arranged an experiment where light raced electricity what would be the results? Let's say a red laser is fired at the same time a switch is closed that applies 110 volts to a 12 gauge loop of ...
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Why doesn't the brightness of a bulb change with time?
Household bulbs get alternating current, which means that the voltage of source and current in circuit keep changing with time, which implies that the power supply isn't constant. However, we don't ...
user181531
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What causes electrical boxes to hum?
Often times you pass by an electrical box on an electrical pole and you hear a distinct hum emanating from it. What causes that tone? Does the flow of electricity itself have a sound? Or does the flow ...
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Is electricity really the flow of electrons or is it more involved?
I am new to the physics category of the Stack Exchange site. I apologize if my question is wrong, too broad, simple, or worded incorrectly. I am just trying to figure out what is true and false when ...
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If the Earth is a good conductor of electricity, why don't people get electrocuted every time they touch the Earth?
Since the Earth is a good conductor of electricity, is it safe to assume that any charge that flows down to the Earth must be redistributed into the Earth in and along all directions?
Does this also ...
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Can lightning be used to solve NP-complete problems?
I'm a MS/BS computer science guy who is wondering about why lightning can't (or can?) be used to solve NP complete problems efficiently, but I don't understand the physics behind lightning, so I'm ...
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Birds sitting on electric wires: potential difference between the legs
We have seen birds sitting on uninsulated electric wires of high voltage transmission lines overhead without getting harmed, because sitting on only one wire doesn't complete any circuit.
But what ...
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Since cables carry electricity moving at the speed of light, why aren't computer networks much faster?
Why can't cables used for computer networking transfer data really fast, say at the speed of light?
I ask this because electricity travels at the speed of light. Take Ethernet cables for example, I ...
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When jumping a car battery, why is it better to connect the red/positive cable first?
When jumping a car battery the standard advice is to connect the red (positive) cable first. What's the physics explanation for this?
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What are the fields produced around a current carrying conductor?
If you consider a current carrying conductor, every instant an electron enters the conductor, another electron will be leaving the conductor. Thus, the current carrying conductor will not be charged (...
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Why can no other chemical elements be used for making a light bulb filament?
As far as I can see from this Wikipedia article on the incandescent light bulb, there have been only four types of light bulb filaments: those made of carbon, those made of osmium, those made of ...
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What is the difference between electric potential, electrostatic potential, potential difference (PD), voltage and electromotive force (EMF)?
This is a confused part ever since I started learning electricity. What is the difference between electric potential, electrostatic potential, potential difference (PD), voltage and electromotive ...
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Why do gases conduct at low pressure?
My intuition tells me if gases conduct electricity, it should happen at high pressure, then the atoms will be closer together and electric field can ionize them.
But my textbook says low pressure is ...
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I touched a tree that was touching an electric fence and got an electric shock. How is this possible if wood is an insulator?
I touched a tree that was touching an electric fence and got an electric shock. How was this possible if wood is an insulator?
The tree wasn't wet either, and it was a pretty strong shock too.
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What causes the direction of lightning flashes?
During a lightning strike, the flashes appear as cloud to ground or cloud to cloud. Why is this the only manner of propagation? Why do the flashes not go upwards from the clouds into the sky?
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Lightning strikes the Ocean I'm swimming in - what happens?
I'm swimming in the ocean and there's a thunderstorm. Lightning bolts hit ships around me. Should I get out of the water?
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Electricity takes the path of least resistance?
Electricity takes the path of least resistance!
Is this statement correct?
If so, why is it the case? If there are two paths available, and one, for example, has a resistor, why would the current ...
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How does load affect frequency on the power grid?
This story about the use of battery/freewheel based Frequency Regulators confused me about how the 60hz frequency of the North American power grid was set--saying that it was kept at that frequency by ...
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Can a gym be built to supply electricity to homes? [closed]
A moving magnet induces a current in a conductor, then shouldn't we be able to generate electricity through manual labour?
I was thinking about building a gym that used magnets as weights. People ...
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Static electricity and door handles
I have a pair of shoes, which seem to isolate me from the ground. In effect I'm gathering static charge and every time i grab an aluminum door handle, that current discharges and that hurts. Ouch.
I ...
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Why is there an electric field in a wire even though it is a conductor?
If you take a perfect conductor, there cannot be a field across it since if there were, the particles would arrange themselves in a way to cancel out the field right?
Yet, why does the same not hold ...
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What does the notation $8.9875517923(14)$ mean? [duplicate]
The number $8.9875517923(14)$ appears in Coulomb's constant. I have read that it has something to do with the uncertainty of the accuracy of the number but answers have been unclear.
Can somebody ...
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Please help identify this physics apparatus!
This was my grandfather’s and have no idea what it is only that it is some piece of physics equipment!
The main black cylinder doesn’t seem like it wants to rotate but not sure if it should?
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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 ...
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Why do metals have free electrons?
Throughout my highschool classes, I have been made to learn that metals have free electrons that's why they are able to conduct electricity.. But I never understood why. Is that related to metallic ...
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Why does a glass rod when rubbed with silk cloth aquire positive charge and not negative charge?
I have read many times in the topic of induction that a glass rod when rubbed against a silk cloth acquires a positive charge. Why does it acquire positive charge only, and not negative charge?
It ...
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How to avoid getting shocked by static electricity?
sometimes I get "charged" and the next thing I touch something that conducts electricity such as a person, a car, a motal door, etc I get shocked by static electricity.
I'm trying to avoid this so if ...
user1667
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If air cannot conduct electricity, how can lightning happen?
If air cannot conduct electricity, how can lightning happen?
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Why is capacitance defined as charge divided by voltage?
I understand that capacitance is the ability of a body to store an electrical charge and the formula is $C=\frac{Q}{V}$. What I don't understand, however, is why it is defined as coulomb per volt. Of ...
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Why does my wife's skin buzz when she's using her laptop?
When my wife uses her laptop, if I touch her skin, I can feel a buzz. She doesn't feel the buzz, but she can hear it if I touch her ear.
So I'm guessing it's a faulty laptop, and she's conducting an ...
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In aluminum, how does electricity travel through the surface oxide layer?
Suppose I connect a conductive wire (cross section 1 mm$^2$) to an aluminum object. Since aluminum is highly conductive, electricity will flow smoothly inside the object with little resistance. ...
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Why are the electric force and magnetic force classified as electromagnetism?
I confuse the four kinds of fundamental interactions, so I think the electric force and magnetic force should not be classified as a big class called electromagnetism.
Here is my evidence:
The Gauss ...
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Is it possible to overload a lightning rod?
A couple of weeks ago we had a big storm roll through the Chicago area. I watched as the city's skyscrapers were struck multiple times by lightning throughout the night and told my coworker about it ...
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