What is Electricity: Definition and 999 Discussions
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell's equations. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others.
The presence of an electric charge, which can be either positive or negative, produces an electric field. The movement of electric charges is an electric current and produces a magnetic field.
When a charge is placed in a location with a non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. If the charge moves, the electric field would be doing work on the electric charge. Thus we can speak of electric potential at a certain point in space, which is equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is typically measured in volts.
Electricity is at the heart of many modern technologies, being used for:
Electric power where electric current is used to energise equipment;
Electronics which deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies.Electrical phenomena have been studied since antiquity, though progress in theoretical understanding remained slow until the seventeenth and eighteenth centuries. The theory of electromagnetism was developed in the 19th century, and by the end of that century electricity was being put to industrial and residential use by electrical engineers. The rapid expansion in electrical technology at this time transformed industry and society, becoming a driving force for the Second Industrial Revolution. Electricity's extraordinary versatility means it can be put to an almost limitless set of applications which include transport, heating, lighting, communications, and computation. Electrical power is now the backbone of modern industrial society.
This is probably a problem with semantics.
The textbook that I'm using has the title "Current Electricity". The corresponding syllabus has the title as "Current of Electricity". Is there a difference between the two titles? Would "of" in the middle make a difference or used in another...
How far could the study of physics have advanced without the discovery/invention of electricity and electrical power?
Or in other words, what fields and major breakthroughs could not have been achieved without the availability or knowledge of manipulation of electricity?
Hello all,
I would like to know a method to trap light. That is, it should be pretty simple and non-electric. It doesn't need to trap all light, just part of it at the least. It should also be able to give out light by itself if certain conditions are met (which conditions do not really matter...
I have a question concerning the generation of electricity and equal and opposite forces.
I've been having a hard time describing it. Sorry if I don't get my point across.
If I start off with using a generator to generate charge in capacitors, I have the equal and opposite forces being the work...
Difficult Introductory Electricity Circuit Problem -- Capacitors
Homework Statement
The Attempt at a Solution
This problem was very difficult, and the most I could do was re-arrange the circuit into a make-shift Wheatstone bridge with all capacitors instead of resistors/voltmeter...
Homework Statement
A relay is required to operate 800m from its power supply, The power supply has negligible internal resistance.
The relay requires 16V and a current of 0.60A to operate
A cable connects the relay to the power supply and two of the wires in the cable are used to supply...
Homework Statement
A circuit consists of 230V supply, a switch, a 2mH inductor and a 12k ohm resistor in series
When the switch is closed at time t=o, a current i begins to flow in the circuit: The current is modeled by the following equation:
i= v/r (1-e^-Rt/L)
Determine the...
Other people must have come up with this before, but what if we attach a lever to a rotating fan. The lever can be attached to a bulb to run it, or maybe something like a Leyden jar or a KERS, (mind me if its the wrong device, i am just a rookie) to store it. So won't the house be self sufficient?
Homework Statement
A charged particle moves in a straight line through a particular region of space. Could there be a nonzero magnetic field in this region? In either case, include a sketch as well as prose in your justification.
Homework Equations
The Attempt at a Solution
The...
So I took honors level introductory physics courses my first year. Here are the descriptions.
I did worse in the second course than the first. This coming year I will be taking intermediate level courses for these topics. The difference is that I will have both Intermediate Mechanics I and...
I would like to ask the experienced experts about the safe limits for AC and DC currents to be used in intro physics labs. People say DC is dangerous because one can’t let go of the wire if the wire was carrying certain DC current.
Following link has a chart with current limits for AC and DC...
Hi,
I'm an automotive technician. I have trouble understanding a couple basic electrical concepts.
The problem is that I am more or less taught that current flows through CIRCUITs.
When analyzing electrical problems, I think current will only flow if there is a voltage (potential...
Homework Statement
So four wires are arranged in a square and all carry the same current "I"
They are all the same distance apart. The two on the left are coming out towards you "O" and the two on the right go away from you "X"
I knew I would need kI^{2} divided by distance, but I"m not...
A bird perches on a bare high power line and nothing happens to it. A man standing on the ground touches the same line and gets a fatal shock. This is supposed to be because there is potential difference between the ground and the line which the man touches but similarly, isn't there also a...
Hi
I want to know what is the diffrences between E=σ/2ε0 & E=σ/ε0
of course I know we use the first for a very huge page but what about the second formula?
I saw in some solving of question when we have 2 pages infront of each others we use both of them...
I want to understand the deep...
how can magnetism be derived from electricity at the sub atomic level??
how is the magnetic field generated around an electron?
if magnetism is just generated due to angular momentum of the electron it is said that if calculated the spin of electron would exceed light speed ; so will it work...
MIT has a Physics Demo called "Rubber and Glass Rods with Tinsel and Balloon"
(Not sure if I can post links but easily found on youtube). I have watched the video several times but am a bit puzzled.
First the lab technician charges the rod by friction but then when he moves it close to the...
Hi.
I have a problem understanding a question for my electronic engineering course. We have a subject that's directly translated to 'the knowledge of electricity and measurement techniques'.
I do hope this is the correct forum to ask for help at.
Homework Statement
Given the...
First of all, excuse me if this question is too basic: I feel like it shouldn't be a struggle to understand, but the fact is it is.
We put up an antenna to play with radio a little, and someone we were working with showed us that there's a reading on the voltmeter without any of the equipment...
Homework Statement
When you rub a gold sphere with rabbit's fur, the gold takes on a negative charge (and the rabbit fur positive). Suppose the gold sphere has a mass of 190.0 g and it obtains a net charge of 0.540 μC. Calculate the ratio of the number of electrons added to the gold sphere to...
I was wondering if and/or how one would could calculate the the generation of static electricity between 2 materials.
For example material A is immersed in substance B and moves within it at a constant velocity. Knowing the velocity and volume / surface area of material A and the electron...
Is there a simple way to "make" static electricity from an AC outlet? Looking for a way to make my hair stand (what is left of it) on its end for an experiment. Thanks for your comments in advance.
Hello, I am looking for a basic introductory textbook on electronics. Since it's introductory, nothing too rigorous required.
Topics:
Basic AC/DC introduction
Current, Charge, Voltage
Resistors
Series/Parallel circuits
Ohm's Law
Capacitors
Semiconductor devices (diodes, doping...
Hello all, I watched a youtube video where you can rub a plastic tube on your hair, and the static electricity generated will pull a stream of water falling from a faucet.
My question is, how would this be possible to do electrically? Meaning, using electricity or a battery powered...
Hi
I have seen electric technicians while racking out high tension circuit breakers, use a wire that has one end grounded and they use the other end to touch the bus bars on the breaker in case of a static charger, they carry out this procedure before they do any work on the CB in case they...
Hey guys! I'm trying to get a bettter undesrstanding of how the electric circuits work. But I do have a rather simple question. So, in the internal circuit we give energy to the charge. Let's say that I have an electricity source and two resitors, like this:
So when passing through circuit...
I know that magnetism can be explained as the relativistic interaction between say a current, and a moving charge. My question however is twofold, is magnetism nothing but electric forces when relativity is taken into account? If the answer is yes, does that make magnetism a sort of psuedo-force?
Thirty years after learning E&M from the wonderful book by Purcell, I noticed that the copyright page of my dog-eared copy of the 1965 edition includes a notice stating that it is available for use by authors and publishers on a royalty-free basis after 1970. The book has gone through two more...
I am a computer science major and we are required to take two semesters of physics. First semester is based on mechanics and the second semester is focused on electricity and magnetism. I was wondering how these topics are used in computer science and in what specific area? I have tried looking...
Like the title says I was wondering if it would be possible to generate a couple of watts of electricity from a kerosene or gas mantle. Less than 0.5% of the energy in the fuel is being converted to light which means that in the 33kJ per mL of kerosene nearly 9 watts is being lost as heat...
The little wicks placed at the wingtips to get rid of static electricity on the wings and body of the aircraft are vital to aircraft.
I am interested in what the certification requirements for placing these ont he wings. I assue the formula of would include things like
1-surface area
2-speed...
What is the difference between magnetic resonance and magnetic induction when it comes to charging devices and other types of wireless electricity. I was doing some research on this but was not able to find a clear answer. If someone could help me with this that would be greatly appreciated...
Homework Statement
Using physics knowlege, why do some electricity pylons collapse in extreme temperatures.
Homework Equations
The Attempt at a Solution
Don't know the physics formulas or equations that could be used. High winds would force the pylons to collapse as the structure hasn't been...
Hi all,
Let us say I have rubbed cat fur with nylon. Is there any relation for determining the amount of charge (in Coulombs) induced on either of the materials?
Thanks in advance.
Homework Statement
A force eld E has the spherical components
Er = (2Dcosθ)/r3 Eθ = (Dsinθ)/r3 E\phi = 0:
(a) Evaluate by line integration the work it does in taking a point (parti-
cle) from point A in the diagram to point B via the quarter circle r = a; 0 <...
Separate question. Can anyone tell me what the limitations would be of trying to convert the planet's ever increasing heat into electricity. I'm imagining building materials that could take 100-120 degree heat and convert it for use in running home appliances, including air conditioners. How...
So I'm a physics major in my second semester of undergrad physics and have been completely blown away by electricity and magnetism. The stuff just amazes me.
So I was wondering what the current hot topics of E&M are. What are the unanswered questions? What kind of things would I be...
Homework Statement
The ac circuit has 3 components in series: a Capacitor C=120μF, an Inductor L=100mH, and a resistor R=7Ω.
A) Find the amplitude of the voltage across the resistor R in the LCR circuit below, when
operated at a frequency of 45 Hz?
B) What is the phase difference...
Hello, I have started reading a beginners book (from the "stop faking it" series) on electricity and magnetism. Its supplied with funny little experiments to help me understand the topic. But I have trouble understanding the intimate relationship between electricity and magnetism. I believe I...
So,
I don't want to disclose why I want to know about this because its to do with a friends invention and it would be unfair to publish too much information without his consent. That's my disclosure so to speak.
I'm interested in how static electricity is managed in vehicles. I remember...
Greetings PFers
I’m thinking about building a Tiny House similar to the one below, except outfitted with solar power.
http://www.tumbleweedhouses.com/products/weebee/#ad-image-0
A Tiny house is a small (~120 sqft) home on a trailer bed. I’m interested in designing one that is equipped with a...
I am sure this is a set of naieve question first of all. However i'd appreciate someone taking the time to enlighten me, as my mind is boggled by this and has been for some days now. I have watched numerous videos on the subject of electricity but am still somewhat confused. My issue is taking...
hey everyone, I have a questions, that is very general, and perhaps, silly... but why are coils so significant in terms of electricity and magnetic fields? why is it when you push a magnet through a coil, you get a charge, but not when you touch it to a straight copper pipe? Or when you see...
As technology has advanced, we have come up with ways to produce and use more energy, and have come up with many different ways of doing so.
Most of what I know of using energy for households or factories or big machines is that they use electricity, as a way to convert fuel, heat, wind...
Is there a way to harness electricity from a steel ball bearing moving through a magnetic field?
The ball would be heavy enough to move through the entire magnetic field (downhill) from end to end without being caught in the magnetic field.
Would having 2 copper rails supporting the ball...