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.
Ok so I understand how a voltage source works, with electrons flowing from a high potential to a low potential. But I'm a little confused about solar cells. So the way they work is that an incoming photon strikes an electron and gives it enough energy to break free and create a current. But...
We were given holiday homework from our teacher, but I'm not sure if we were given the proper tools to solve it. Is it only a formulas game? If so, how close am I to not being embarrassingly wrong?
Homework Statement
An electrical engine that requires a flow of 5 A with the useful power...
Hi,
Originally I had a question about a wire that allows electrons to move to higher voltage. I could not figure out why the wire does not lose electrons to the point it runs out.
The question was answered on these forums when someone mentioned salt bridges, which lead me to watch some video...
Nikola Tesla observed that electrons transmitted through a near perfect vacuum in his vacuum tubes appeared as corona several feet through the air surrounding the tube. He thought that if there is nothing in the tube between the electrode and the glass then how do the electrons convey through...
I've always been given conflicting messages like that we only use conventional current because they were confused years and years ago. Anyway I'm wondering if 'electricity' is the flow of electrons or "electric charge" like I heard once, I assume they meant like a flow of empty valency shell...
I think I remember reading somewhere that almost every moment of our lives we are surrounded by thousands of volts of ambient static electricity caused by the movement of air and clouds, it's just that we don't notice it. I may have mixed up my information so I'm just asking for clarification...
Homework Statement
A 19-cm-long nichrome wire is connected across the terminals of a 1.8 V battery. If the current in the wire is 2.1 A, what is the wire's diameter in mm?
Homework Equations
R = Rho*L
--------
A
v=ir
The Attempt at a Solution
rho for this = 100...
You have a positively charged rod and you have a neutral metal sphere hanging on a wire.
If the positively charged rod approaches the sphere, the sphere will be repulsed - correct?
Hi,
The UK., electricity supply is 13 amps at 230 volts. With such a current and e.m.f., how can we run appliances which don't need that e.g., a hairdryer with a 3 amp fuse. What stops the full 13 amps overwhelming the appliance? My question is not well put but I'm sure you know what I'm...
I need help understanding this conceptually, so can anybody please correct me and help me understand this?
If I'm correct then just say so.Diagram: http://i324.photobucket.com/albums/k327/ProtoGirlEXE/labVpic3.jpg
the circles are bulbsOk so the basically in an open circuit there is no flow and...
Hello,
I am preparing a material about static electricity, and it's basically finished. However, I have a question what puzzles me. I hope people in this forum can fill that in.
So, the core process is that electrons hate to float in the insulators, so they hang on the surface of those...
Current electricity...
Homework Statement
In the circuit shown(please refer to attchment) only thing missing is that the battery has an internal resistance of r. Now When key K1 is closed the ammeter reads I0 whether K2 is open or closed. But when K1 is open the ammter reads I0 /2 when K2 is...
Homework Statement
Please refer to the diagram(attachment)...the circuit contains two resistors in series of 25 and 15 ohm respectively and there are two batteries of emf 10 V and 5 V respectively ...Only thing missing in the diagram is that both the batteries have internal resistances of 2.5...
I think what I am doing is pertaining to ohms law but I'm not sure because we're not suppose to rely on equations or literal physics terms, but when we learned from previous labs. So this is mostly conceptual and I want to make sure I'm thinking through this correctly.
Diagram 1...
How is static electricity charge distributed over the human body if skin (1100 - 496,000 ohms) is a good insulator? For example, if one wears rubber-soled shoes and walks around on a rug, the shoes will obtain a negative charge. Then, if one touches a doorknob or some other metal object, a spark...
As an assignment i need to figure out the most efficient way to convert heat to electricity and so i searched through the internet and came across Prof. Hagelstein's work which is called semiconductor technology. In short, the technology is based on the principle of thermionics by replacing a...
Homework Statement
Refer figure
Note: ~ stands for proportionality sign and p stands for resistivity.
The Attempt at a Solution
R=pl/A
Rnet~l2/A
V is constant across each conductor, so magnitude of electric field must be constant for every case. Since drift velocity depends on electric...
I have a few questions.
Which word came first, electricity or electron?
I just learned that the electron was "discovered" in 1897. That's significantly after electricity had been "harnessed" for practical use. What did contemporary scientists/science books say electricity was?
I just read the following innocent sounding statement, which got me thinking:
"An electron in motion relative to an observer generates a magnetic field..."
This implies that, for an observer moving alongside at the same speed as the electron, there is no magnetic field. I understand the...
Hey all. I'm trying to find more info on converting moving ions into electricity. AKA Direct Energy Conversion. Anyone know any good sources? I don't really understand how they do it yet, even after reading a few things I found on google.
Hi
I reside in India and last month , our electricity bill was Rs 510 for 163 kW-h
Converting to US dollars, it is US$ 23021 at current exchange rates. So the rate is
$ 141.24 / kW-h . I want to know what is the cost of electricity around the world for
1 kW-h.
Homework Statement
An equilateral triangle has sides of 0.11 m. Charges of -8.6, +8.0, and +1.5 µC are located at the corners of the triangle. Find the magnitude of the net electrostatic force exerted on the 1.5-µC charge.
Homework Equations
kqQ/d^2
The Attempt at a Solution
first...
PLEASE help me by telling me if the following is true (below, when I say going with the flow I mean following the direction of electric field, and when I saw going against flow I mean going in opposite direction of electric field)
Positive charges go with the flow
Negative charges go against...
Homework Statement
Three resistors, 21, 43, and 73 , are connected in series, and a 0.55 A current passes through them. What is
(a) the equivalent resistance and
(b) the potential difference across the three resistors?
Homework Equations
i tried to use EPE/q by putting the equivalent...
ELECTRICITY GENERATION THROUGH THE CONVERSION
OF ENERGY PRODUCED BY REVOLVING
GEARS OF A TURNSTILE
As the title implies, do you think it's feasible?
I'm working on it as a topic on my research subject, but I'm having a hard time. I didn't know that there are lots of principles involved...
How much E&M is involved in a MechE degree? I'm a high school senior in AP Physics C: E&M and I hate it with a passion. I loved Mechanics, but E&M is terrible. Would I just need to take the one required class (Physics 2), or do I need to use multiple E&M concepts throughout undergrad? I am...
Homework Statement
we wish to measure the resistance of a lit light bulb. Unfortunately, the resistance of the light bulb when hot is not the same as when it is cold. when the light bulb is turned on it becomes hot. we cannot easily measure the resistance of the light bulb when it is on (hot)...
I'm trying to replicate MIT's "Witricity", but on a smaller scale. I have a coil connected to a function generator and then a second coil (with more loops than the first) connected to an LED. So I guess now I have a transformer. And the LED lights up when the coils are up to 10cm apart. I...
Homework Statement
Constants Given
Colombs constant = 9 x 10^9
Charge of Proton = 1.6 x10^-19
Proton rest mass=1.673 x 10-27
Charge of electron = -1.6 x 10^-19
Electron Rest Mass = 9.11 x 10^-31 kg
Homework Equations
On the attachement
The Attempt at a Solution
On the...
Physics Grade 12 HELP! Electricity Unit
I have attached the question paper with this post
Homework Statement
v=2 x 10 ^ 5 m/s
Volatage=250 or 500?
Constants Given:
Coulombs constant = 9 x 10^9
Charge of proton/electron = 1.6 x 10^-19/-1.6 x 10^-19
Proton rest mass 1.673 x 10^-27 kg...
I apologize, I wrote all of this out in a word processor before attempting to post it and I did not notice that there is a template for giving problems. I hope you forgive me, my posts tend to be wordy and take awhile to write; attempting to write it in the text box would result in the server...
If I have a really big charged object, is it possible to direct the charges to an object/the same place and generate current/electricity from it? It was just something I thought of, totally random, but I'd like to know the reasoning behind it C:
i was pondering over a few questions
1) if i were to connect a wire from the positive of a power source, and touch the other end to myself, would i get electrocuted? common sense tells me i will, but where is the close circuit? does electricity flow from source to me to the earth? and then...
Homework Statement
The lines show the equipotential contours in the plane of three point charges, Q1, Q2, and Q3. The values of the potentials are in kV as indicated for the +5, 0, and -5 kV contours. The positions of the charges are indicated by the dots...
Although I'm sure people have been looking to develop a solution like this since the beginning of time (at least, the first use of electricity), I'm trying to achieve a design that will enable perpetual electricity generation without the addition of conventional energy inputs. Essentially, I'm...
Homework Statement
How would static electricity on your clothes or on your body affect an experiment involving charged objects?
Homework Equations
Coulomb's Law
The Attempt at a Solution
The static electricity would attract the objects due to the like charges, assuming the objects...
Static electricity in outer space? Somewhere I read that a space vehicle traveling in outer space picks up a static electricity charge. Is this true and if it is true, where does that static electric charge come from?
I came across a report entitled "Wind Farms Provide Negligible Useful Electricity" by Richard Courtney. You can google it its just available free on the internet.
What I wanted to know, if anyone here works in the power grid industry, was it true or should it be taken with a pinch of salt...
Hi everyone.
I want to heat a piece of Rubber by embedding copper strips or wires in it and passing electricity(120V - 2.5Amp) through it. The room temperature is 0(zero) deg Celsius and i want to heat the aluminum block(5" x 5" x 1") to 10 deg Celsius(Not more than 10 deg).
Question...
Hello, I am a student making a generator.
the main idea is to use the vibration with the magnet coil setting with the spring to generate electricity.
I will use the permanent magnet, but i know that
e = N w B A
i decided to have a 12Volt output,
constant vibration frequency in 100Hz
the A...
Homework Statement
A toaster, which uses 6 alkaline D batteries, must produce at least 900 W of thermal energy. D cell batteries have a capacity of about 5 Ah. How long can the batteries run the toaster?
Homework Equations
The Attempt at a Solution
Well I know that Power is (J/s)...
hey everyone I am new to the site an new to physics ( bare with me if I am not as smart as some ) , =)
ok, i have this friend who is world widly known for his work, but cut this short, he uses electricity an crystal an can do some out of the ordinary stuff with this he has been in numerous...
Homework Statement
The potential caused by an array of charges in a region of space can be described by the equation V(x,y,z)=2x+xy+y2-xz2 volts, where all distances are measured in metres. If a charge of 2 mC is moved from the position r1=(1,2,0)m to r2=(3,1,0), calculate the resulting change...
Hi,
Recently I've become interested in the possibility of using magnets to generate electricity, a "magnet motor" if you will. There are evidence of a lot of different attempts on the internet as well as a number of actual patents for these motors.
When I say "magnet motor" I mean a...
If my memory serves me right I recall once someone said something like that in England or the UK electricity rates varies during 24-hour period. It costs more during nighttime than during daytime. Is this true? What is the rationale behind this? Please let me know. Thanks.
Hello, my name is Kevin and I going to be adding electricity to a barn about 1000ft away from my house. The barn will act as a second home and will need to be using around 2-10KWh. I figure it will never exceed 10KW per hour. I will be running it underground in heavy duty poly casing. My...