My basic understandings of electricity - Page 1
Forum section: electronics / beginners

author: ENIAC
author_rank: Contributor
timestamp: January 17, 2015, 06:48:52 pm
content: I am trying to understand what exactly electricity is. From what I've gathered essentially it's the flow of electrons from atoms. From the stand point of hydroelectric power water flows down a shaft and turns a turbine which thus spins a rotor with a magnet attached to it. Outside the magnet are copper coils. This produces electricity?I don't quite follow what happens when the magnet spins inside of copper wires? Do the electrons go into the copper wirings and start moving?Also, once they move and create current how does this say make a motor spin or a light bulb come on. That's one thing I can't seem to understand. How the moving of electrons can cause anything to start moving.Thank you

author: devanno
author_rank: Regular Contributor
timestamp: January 17, 2015, 06:59:16 pm
content: I am going to take anunscientifichigh-level view here to maybe help at a conceptual level.At the hydro plant (or any plant that can spin a turbine... so water pressure, steam (which includes fired and nuclear plants)), you are converting rotary motion via magnetism into an energy stream that just happens to be made of electrons moving in a material that is very able to release electrons from their bonds (a conductor) ... and at the other end, those electrons are run through coils and create a magnetic field and convert their energy stream back into rotary motion. Likewise, these electrons can be run through materials that have various resistances (like a light bulb filament) that reduce the energy as heat, while said filament reacts by releasing photons.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 17, 2015, 07:08:25 pm
content: A very, very crude analogy might be,Consider an impeller in a water stream. When it turns, it throws water around, creating fluid motion.Electrons in conductors are a sort of fluid, and behave along similar lines; the magnetic field acts as an impeller, forcing them into motion.The most obvious difference is, this is achieved without physical contact, and fields penetrate volumes (whereas the impeller only acts through its surfaces that are exposed to the liquid). The second obvious difference (obvious, once you start playing with magnets and wires, anyway), is, magnetic fields induce motion at right angles -- which is why a magnetic core goes along the axis of a solenoid, while the wire is wrapped around it, not parallel to it.Tim

author: IanB
author_rank: Super Contributor
timestamp: January 17, 2015, 07:11:54 pm
content: Where are you in your educational progress, and how much science and physics have you been introduced to so far? Knowing this may help us to explain things at the right level.One thing to make clear is that nobody, even the most advanced scientists, really knows "how" things happen. On some level, what happens in physics is like magic. How can one magnet attract another magnet, when the two magnets are far apart and not touching, and there are no strings attached? It is mysterious, and not something that can be explained in terms of anything simpler.What happens in science is we observe what happens, and we find out how to describe what happens with rules: if I do this, then that will happen. We make note of all the rules and we use those rules to make predictions. In engineering we use the rules to help us design and create useful things.One thing we can observe is that there is something called "energy". We can account for energy in all its forms, so that no energy is ever created or lost, it is only changed from one kind to another.In a hydro plant, the water in the reservoir has gravitational potential energy. When this water flows down the pipes to the turbines the potential energy gets converted into the kinetic energy of motion. When the fast moving water hits the turbines, the kinetic energy of the water is transferred to the turbine, making it spin. When the spinning magnetic fields in the turbine intersect the wires in the coils, the moving magnetic fields make electricity move in the wires, converting mechanical energy to electrical energy. And so it goes on.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 17, 2015, 07:24:45 pm
content: Quote from: IanB on January 17, 2015, 07:11:54 pmAs long as Feynman seems to be trending these days (a phenomenon I don't mind at all),Tim

author: ENIAC
author_rank: Contributor
timestamp: January 17, 2015, 08:16:02 pm
content: Quote from: IanB on January 17, 2015, 07:11:54 pmMy education needs improvement, I've taken physics/chemistry before but probably should have listened better. Never took electronics or learned about circuit boards. My math is currently at precalculus level.I understand from that quote that energy can take on many different forms, and can be converted many different ways. Gravity pulls water down so that's the gravitational energy water hitting a turbine is kinetic energy and moving around the rotor is mechanical which can turn into electrical, is all that right? And electrical energy is very versatile because we have so many contraptions which can change it from. My main confusion is what's happening when the rotor spins the magnet inside the coil? What phenomena is this called? Is it the electromagnetic field? I don't understand exactly what the moving magnet fields do to create electricity.Thank you

author: IanB
author_rank: Super Contributor
timestamp: January 17, 2015, 08:30:03 pm
content: Quote from: ENIAC on January 17, 2015, 08:16:02 pmThe phenomenon is called electromagnetism.You can imagine the electrons in the wire, as Tim said, as a kind of fluid. Electrons can be made to "flow" along the wire if a "pressure" is applied in the form of a voltage difference between one end and the other.But electrons have a charge on them, which means that they can be influenced by a moving magnetic field. When a charged particle like an electron is inside a moving magnetic field it experiences a force that tries to make it move. So when you have a wire full of electrons inside a moving magnetic field, the moving magnetic field pushes the electrons along inside the wire, causing electric current to flow. It's as if a "pressure" is being applied to the electrons from outside the wire.In terms of energy transformations in a generator, the mechanical energy of the rotating generator is being transformed into the electrical energy of moving electrons. This energy transformation is real and can be felt. If you have a freely spinning generator and you attach a load to it, for example a bulb, the generator will slow down as the bulb draws power from the motor.Sometimes you can see this in a car. Have the engine running at idle and then turn the headlights on. You may hear the engine note change as it slows down with the effort of driving the headlights.

author: dmills
author_rank: Super Contributor
timestamp: January 17, 2015, 08:49:35 pm
content: That is kind of the hard part without some fairly high end maths and physics.When a magnetic field changes and the field lines cut a conductor a voltage is produced between the ends of the conductor, this is magic, don't worry about it, you don't have the maths (basically you can think of it as the changing magnetic field produces a net force on the electrons in the conductor moving them towards one end until the electric field between the electrons balances the effect out, electric field is simply voltage per meter).Now when you connect a resistance across the ends of that wire, current flows and the current flowing in the wire produces a magnetic field that acts to oppose the change in magnetic field that produced the voltage in the first place.That is about the best I can do without Calculus.Thus a spinning magnet in an alternator does little work until you apply a load which causes the voltage produced by the machine to cause a current to flow in the windings doing work at the load and (because the two magnetic fields are opposed) causing the prime mover (Turbine, engine, windmill, whatever) to need to put more power in at the power station to maintain system speed.Regards, Dan.

author: ENIAC
author_rank: Contributor
timestamp: January 17, 2015, 08:53:49 pm
content: IanB that's amazing! So those magnetic fields give a sort of JOLT to the electrons thus making them move? What keeps them moving along with copper wires and not just stopping in that spot of where the field is being generated? Or does the entire copper wire become an electromagnet itself which continues that original reaction like a chain reaction maybe?I am still very new all this. Voltage is like pressure which makes them move once they are freed from the atom by waving the magnet fields with it? Because it creates a potential difference aka positive and negative ions? and since atoms are always trying to find an equilibrium electricity exploits this facts and makes them work to get to point A to point B? and the work from moving from those two points is what creates electricity?If that is right, then one end of the copper wire (probably wrong) has many positive ions or those deficient in electrons and the other has many negative ions or those with excess electrons? and that creates a sort of back and fourth/throw and receive effect?

author: dmills
author_rank: Super Contributor
timestamp: January 17, 2015, 09:12:05 pm
content: Not quite, in a solid conductor the notion of an ion does not (to a first order) apply as the atoms are effectively held in place by the bonds to other atoms in the crystal lattice (Current flow in a electrochemical cell is a different matter).There are however electrons that are free to move, and the changing magnetic field moves some of them, such that the force from the magnetic field and the net force from the electric field due to the uneven electron distribution balance, that electric field produced by the uneven distribution of electrons gives rise to what we see as the voltage produced by the machine.It is interesting to note that the bulk drift velocity of the electrons in a copper wire is tiny (less then 1cm per second even at high current), it is the electric field that propagates at a significant fraction of light speed, not the electrons themselves).Regards, Dan.

author: AndreasF
author_rank: Frequent Contributor
timestamp: January 17, 2015, 09:15:05 pm
content: Quote from: ENIAC on January 17, 2015, 08:16:02 pmThe proper term is "magnetic induction".

author: radiomog
author_rank: Regular Contributor
timestamp: January 17, 2015, 09:21:07 pm
content: I will never forget the first day of my first Electronics class.. the instructor had this to say:Quotefor some reason, thats stuck with me

author: orin
author_rank: Frequent Contributor
timestamp: January 18, 2015, 01:03:05 am
content: I'd suggest taking a look at this online course:https://www.edx.org/course/electricity-magnetism-part-1-ricex-phys102-1xYou shouldn't need any calculus to start with, but you might want to brush up on your math skills. It only just started this week. You don't have to do the homework, just watch the lectures if you want.

author: tautech
author_rank: Super Contributor
timestamp: January 18, 2015, 01:22:51 am
content: ElectroMotiveForceGoogle EMF

author: Nerull
author_rank: Frequent Contributor
timestamp: January 18, 2015, 04:31:47 pm
content: Quote from: ENIAC on January 17, 2015, 08:53:49 pmElectrons move when exposed to a an energy gradient - what we call voltage. Just as gravity pushes a ball down a hill, electrons get pushed along a conductor placed between different charges. One thing you may be missing is that electricity, the way we use it, always flows in a loop. The generator isn't turning kinetic energy into electrons and forcing them through a wire, its turning it into a difference in charge. Connect a wire from one end of the generator to the other, and electrons will flow due to this charge difference. Make this wire loop through half of town and through any devices that happen to be connected along the way before coming back, and the same thing happens.Different conductors can work in somewhat different ways, but the ones we are most familiar with are metals. Metals make excellent conductors, in general, because electrons move freely through them. The outer 'shell' of electrons are in a metal atom aren't actually "attached" to the atom - called delocalized electrons - they just sort of drift around through the metal, shared by all the atoms. These electrons are highly mobile, and move easily when exposed to EM fields. They want to spread out equally through the conductor, so if we add electrons to one end and take them from the other, electrons will flow through the metal until charge is equalized. If we keep doing this, electrons will continue to flow indefinitely.wiki sums it up better than I could:QuoteAnother conductor (which you hope to never see in your electronics) is salt water, an ionic conductor. In this instance charge is transferred by the movement of entire ions, not by the movement of electrons.The way conductivity works in semiconductors will make your head hurt, so get the basics figured out first.