Can someone explain wattage and voltage, how are they applicable, why are they useful and which one can hurt me?
I have watched many YouTube videos. I understand that electricity is electrons moving through a conductor from “+” to “-“ but am at a loss of why they move and why do we have two measurements for one thing.
Power (watts) and voltage (volts) are not the same thing.
The water analogy is most useful at this level (despite being wrong in most respects, it instils a basic working understanding good enough for the householder).
Think of a waterfall. Wait, think of two: a very high one with just a thin stream of water, and a low one, maybe a foot high with a torrent of water flowing over it (a weir).
Voltage is the height of the waterfall: a stream of water at the bottom of a very high waterfall will feel more painful than a stream from a much lower one.*
Current is analogous to the amount of water flowing over the waterfall - the river's current.
Multiplying voltage by current, you get power: the ability of the waterfall to do useful work.
(A very high waterfall with hardly any water flowing over it won't be able to turn a water wheel very quickly, and nor will a very low waterfall with a lot of water flowing over it. You need both voltage and current to do useful work.)
Re the movement of electrons: in fact they move very slowly on average under the influence of an electric field, but by their "bouncing against" their neighbours, the electric impulse
is transmitted quickly through the conductor.
* An alternative analogue for voltage is water pressure, and indeed in some languages voltage is referred to as pressure.
In Turkish voltage is known both as voltaj and gerilim. Gerilim means tension, coming from the verb germek, which means to stretch. I think tension is a good analogy, and fits with the idea of potential and springs.
THAT is what high tension wires are?! I've always seen it in the context of the massive transmission lines, so I thought it meant that the wires themselves were under high tension from their weight.
Also "high tension power lines," which being heavy catenaries presumably are in high mechanical tension, but must surely have gotten that name from the voltage = tension thing.
German has this too: voltage = Spannung = tension.
This must go right back to the earliest writings on voltage as a concept.
In spanish "Voltage" (i.e. voltaje) is "tensión" (tension) or "diferencia de potencial" (potential difference).
A problem here is that "tension" communicates a concept, but "voltage" communicates nothing, it's only a derivation of the unit used, or perhaps something to do with Alessandro Volta, a gentleman most students these days hadn't the pleasure to meet.
A simmilar problem in spanish was "amperaje" (amperage) which is not much heard any more except very colloquially among electricians; the standard term is "corriente" (current).
However, the units and letters are somewhat confusing for the students:
V(oltage) = E(lectric field?), unit is Volt, is refered as tension of potential differece.
A(mp) = I(ntensity), unit is Ampere, is refered as corriente.
P(ower), unit Watt, is consistent, as is refered as potencia (power).
In Russian it is напряжение. Which can be loosely translated as tension, but more in the sense of a feeling than of a characteristic of a rope or a spring (that's натяжение).
In some languages voltage is called "pressure". I think this is also a good analogy because just like how you get energy from a pneumatic system by exploiting a pressure difference, you get energy from an electrical system by exploiting a potential difference
That analogy would work. In that case voltage (volts) would be the tension on a rubber band, current (amps) would be the width of the rubber band, ad Power (watts) would be the product of tension times the diameter (or mass).
> Re the movement of electrons: in fact they move very slowly on average under the influence of an electric field, but by their "bouncing against" their neighbours, the electric impulse is transmitted quickly through the conductor.
When you apply a voltage across a conductor it generates an electric field, and the electric field propagates at the speed of light (it’s an EM wave). I could be wrong, but I think that is why the electric impulse transmits quickly even though the drift velocity is so slow.
Each electron moves slowly, but they all move approximately in the same direction st the same time, so the net effect is to move charge berry quickly, right?
Like a bucket brigade where everyone passes water to the person on their left. You move a bucket 3 feet per second, but together everyone moves a bucket worth of water a hundred feet per second.
No, this is the whole "confusing the wave and the medium" problem. Drift velocity (the technical name for "how fast are electrons moving through this wire") has effectively nothing at all to do with the propagation of electrical properties through a circuit.
If electrical properties propagated at the drift velocity, there'd be an appreciable delay when you flipped your light switch.
Electrons move because you have an electric field. Like charges repel while opposites attract, so if you have a excess of protons at one point, an excess of electrons at another point, and a wire connecting the two points, then the electromotive force will push the electrons through the wire to try to balance out the charges (see Coulomb’s law [0]).
In the process, the electrons gain kinetic energy, and if you’re clever you can extract this energy to do useful work. Voltage [1] is defined as joules per coulumb, where joules is a measurement of energy, and coulomb is a measurement of electric charge — one coulomb is the charge carried by 6x10^18 electrons. A voltage is always between two points, so if the voltage difference between point A and point B is 1V, then moving 6e18 electrons from point A to point B will produce 1J of energy; or, conversely, it would require 1J of energy to move the electrons back “uphill” in the opposite direction. (Actually, that’s sort of backwards because electrons carry a negative charge and so flow from the negative side of a battery to the positive, but that’s not terribly important right now.)
Current [2] is the rate at which electrons are flowing, defined simply as coulombs per second. You can calculate the rate of energy flow by multiplying voltage (energy per unit charge) by current (charge per second) to get watts [3], which is defined as joules per second.
If you want to learn more, there’s lots of excellent resources online — but if you really want a solid understanding from first principles, you might be better off taking an introductory physics course at a community college.
In a battery, the energy moves through the external circuit because the internals of the battery have been arranged so that an energy releasing chemical reaction is completed when that happens.
Voltage and power are related by current. Power = voltage x current.
The amount of current that flows through a circuit depends on the voltage potential and the properties of the circuit. Our bodies aren't particularly good circuits, so lower voltages won't push much current through a circuit that includes it. A car battery isn't a big electrocution risk, it is dangerous because it can release a lot of energy quickly (it has fairly high power). Somewhere around 50 volts, current does start to flow through our bodies, causing problems even at relatively low currents (and thus low power), heart disruption and such.
Wattage is simply voltage x amperage. It's the law. Watt's Law.
Watts are a measure of energy, just different units than calories or BTU.
Voltage is a measure of difference in _potential_, and amperage is a measure of current being moved. So electrical energy depends on a bit of both.
Beyond a certain voltage, it can be somewhat shocking. High enough and it can jump out at you.
And it can be badly damaging.
Also depends on how conductive you are at the time, conductance is the opposite of resistance.
Also depends on how much amperage is available from the source, if the source is fused for 1 amp maximum it would be less risky than higher amperage fuses.
Like with household wiring, if you get shocked and are conductive enough for significant amperage to be passed through your body, the total wattage could be enough of a fraction of a space heater's dissipation to roast the tissues which are involved with conducting the current.
Simply because there's enough amperage available at that voltage to get a space heater red hot, and the circuit breaker will not trip unless you are conducting more than that.
OTOH, sensitive organs can be upset by much lower amperage if it passes along lines where the organs are nearby.
For instance if you work on an electrical box and take a shock from your right hand to your right elbow, it's mainly going to hurt that one arm.
But contact the same two points, one to each elbow, and the heart is at risk much more than before, since the current has to pass through your torso to complete the circuit.
> Watts are a measure of energy, just different units than calories or BTU.
Sorry to be pedantic, but watts are a unit of power, not energy. Power is energy divided by time. The unit of energy is a joule (or, more commonly in household terms, a Watt-hour).
Wait, is that right? I thought that was one of those "lies to children". I mean, yes, the electrons move (er...drift), but I thought the important thing is that it's the charge that moves, not the electrons.
At least it's not just me that thinks the usual explanations are lacking.
The charge and the electrons are the same thing (at least in a normal conductor). Both move very slowly. But energy moves through them very quickly (fluid analogy is helpful here: when you pump water into a full hose then water starts flowing out of the hose quickly even though it may take a long time for the water you just pumped in to exit. In electricity the difference is even more extreme).
Correct. In a related concept, I had a professor that explained it as a combination of electron flow in one direction, and "hole" [1] flow in the other. Either way of looking at it is valid.
But lightning is where the gas has broken down, turning into plasma. Lightning is a growing conductor, like a motorized antenna on an oldschool car radio.
The growth of lightning is much like a growing metal dendrite-crystal.
Also, when lightning leaps rapidly upwards, the electrons INSIDE the lightning are flowing slowly downwards. The extending tip of a lightning-streamer is not an electric current, it's more like the moving tip of a growing fracture.
> ...mistaking the wave for the medium. Is "electricity" the electrons, or is it the wave of electron-flow, or is it energy that flows THROUGH a column of electrons. Think of how difficult it would be to understand sound waves and air pressure if we had just a single word that meant both "sound" and "wind" and "air."
I think in this analogy, sound is more like voltage in the sense that voltage is like pressure: it’s a measure of potential per electron or force per air molecule. And when you push on the electrons at one end of a wire, that pressure change rapidly propagates to the other end of the wire even without the electrons moving. Like the way sound doesn’t involve air molecules flowing from place to place but is a pressure wave.
Wind is like electrical current in the sense that you set up a pressure difference between one point and another, and then you open up a little path for the electrons/air molecules to flow through, then they will move along that path, and the amount of air molecules/electrons flowing past a point per second is the current/wind. That’s the analogy.
First, set aside wattage for a moment, it's a derived unit.
The key units are amps (current) and volts (voltage aka potential difference). In the commonly used water analogy voltage is water pressure, and current is amount of water that flows through per unit of time.
It's the current that kills you. But voltage and current are related, in many cases by Ohm's law: current is proportional to voltage, with coefficient called conductance (the inverse of which is resistance). That's why high voltage is more dangerous.
Even a question like this isn't so simple. There's at least a couple of ways electricity can hurt you. One is by interrupting the regular body regulation mechanisms, namely your heartbeat. Electricity passing across the heart can cause it to spasm. If it can't recover and find a regular heartbeat again you die. This is the most common way to get hurt and could happen from getting a shock from mains. The other is by electricity passing through you and burning you on the way through. This is common from lightning strikes as the electricity will pass through you to ground, rather than across the heart. It means you're less likely to die, but more likely to sustain injury.
In all cases, what hurts you is current. Current means electrons are flowing through you. As mentioned there are at least a couple of ways that current can affect you adversely. So it needs to be either a large enough current (so more electrons flowing), or a current going in the wrong place (across the heart).
So what makes current flow? Or, why do the electrons "want" to move? Voltage. A car battery has plenty of energy in it that could kill you in either of the two ways, but at 12V there's not enough voltage to get any current flowing through your body.
Voltage is the existence of an imbalance. Electrons "want" to be in a place where they are balanced with a positive charge. A battery represents a structure that is very imbalanced but the electrons are not able to move anywhere until the two ends of the battery are connected with a conductor. There are many ways that these imbalances arise but they are ultimately always the result of energy going in. When the imbalance is resolved the energy comes back out.
To hurt you a voltage also needs to be sustained long enough to pass enough current. A static shock is due to a very high voltage existing which it causes current to flow and why you can feel it, unlike the car battery. However, in an instant all the current has flowed and the voltage is gone.
So the answer is a high enough voltage and enough energy to sustain that voltage. Mains electricity can hurt you because it's high voltage (>50V) and can sustain that voltage all day long. Lightning can hurt you because it's very high voltage and can sustain it long enough (and that's only an instant) to cause serious injury.
Not an expert here but there are not two measurements for one thing. You need to precisely understand basic physics mechanics concepts like force and work before any answers will make sense. BBC youtube series is a great intro.
Electrons are.. we don't really know what they are. What we do know is that they have a "charge" around them, an "electric potential", and that they repel each other.
"Electricity" is one of those terms that doesn't really have a specific meaning. From what i see, we use it to group all the electromagnetic things that.. i guess deal with "loose" electrons.
As for the actual question, first i'd have to explain "electric current". Current (in Amperes) is just the flow of electrons. As in how many electrons flow through some plane over time. In practical terms; how many electrons flow through a wire, where the "plane" is the diameter of wire.
Voltage is a force. Imagine that the electrons weren't points that repealed each other, but were instead balls. You fill up a pipe with balls and push on one side of it. The force you are pushing with is the "voltage". You can also imagine this with water, where the pressure is.. well it's all the same really when we get "low" enough. Note that electrons, unlike balls and water, don't really have mass.
Wattage is power. It is how much energy is.. transmitted over time. You pay your bills in Watt * Hours, but you might as well pay it in Joules. It shows you how much power you can expect from a machine. Wattage is calculated by multiplying Voltage and current, as in how hard you push and how many electrons you push per time. In water terms, it is the speed of the water multiplied by how big the river is (or pipe).
So they are useful units of measurement, just as any other metric unit of measurement. In fact Ampere is one of the seven basic units of measurement in the Systeme international d'unites (SI, often called "metric").
The one that actually hurts you is the current. The thing is that Voltage "pushes" the current, so one might rightfully think that "high" Voltage is the dangerus one. But again you can touch a 100000 Volt sphere on top of a Van de Graaff generator, because it doesn't have enough electrons in it to make a current "big" enough to kill you. The current across the heart, that is enough to stop your heart, is about 50mA (as far as i remember), and that is very little current. Your heart is in between your hands, so you would need to hold "+" in one hand and "-" in another for current to go through it. You can also die from poisoning if a large current burns your flesh, and other similar bad things. If you think there's a danger from electricity, use just one hand so that the current goes through your legs, missing the heart (also watch for the top of your head, because brain). If the voltage is really high, like a transmission line cable falls right beside you, put your feet together and hop away. Like 10 meters away should be fine, idk. To be clear, you can touch the leads on your 12 Volt car battery and nothing will happen to you, in spite of the car battery being easily capable of delivering a big(ish) current of a 100 Amperes (but if you connect the leads with a wire, it will melt and burn you).
For fun i measured my palm to palm resistance just now. It's ~2 mega Ohms currently. So saying i need 50 mili Amps through my heart to stop it, i'd need (V = 0.05 * 2000000) 100000 Volts minimum. But that is for "direct" current (DC, not AC), and it doesn't take a lot of other things in to account. In reality 220 Volts AC could be enough. On the other hand, i know many people survived grabbing the "hot" wire and ground with their other hand, and the only one i vaguely remember died has fallen of a ladder because of the shock.
So in short; Wattage is power, Voltage is.. force, they are used to calculate things involving a lot of stuff (and safety), and the current hurts you because Voltage told it to.
PS Feel free to ask if something is not clear, i misinterpreted your question, something else you want to know or expand upon, etc, etc
I'll try. Some have done a decent job here already.
Watts = volts * current (amps). It's hard to compare words like "force" and "quantity" for volts and amps, but here's maybe a practical definition.
High voltage is dangerous because it can leap through air (arc) to form a circuit. If part of that circuit is _you_ (like, from a high-voltage wire, through you, to the ground), then you can be made dead, quite quickly. That's why high-voltage (sometimes called "high-tension") wires are carried by tall towers with the wires far apart -- if the wires were closer together, they could arc between them and short out.
Essentially, high voltage overcomes insulation -- whether the insulation is air (for high-above-ground wires) or various forms of plastic (for wires buried underground). That's what makes it dangerous, and why electrical panels have warnings that say "Danger: High Voltage".
But even very high voltage won't hurt you if the current (amps) is too low. But "low current" isn't something you typically encounter in, for example, household AC wiring because the supply of current is generally very large.
So high voltage can kill you, but only if the current (amps) is high enough. In most practical situations where you might be exposed to electricity from the grid, the current is plenty high. That's why the signs say "Danger: High Voltage" and not "Danger: High Amps" or "Danger: High Power" (watts).
But how high is "high"?
A 12-volt car battery (I wonder how long that term will be meaningful...) isn't very high voltage. You can safely put your dry fingers across the terminals of a 12v battery and not feel a thing.
On the other hand, the 120-volt (or 240-volt) electricity coming out of a wall socket is most definitely unsafe to grab with your dry fingers. I've been accidentally shocked dozens of times by 120v electricity, and it is attention-getting. It can kill you fairly easily if, for example, the alternating current of the electricity causes your muscles to contract, forcing you to hold on ever more tightly to the wires. Usually, it's your heart in the path of the current that takes the, um, beating. If you get a shock across just the one hand that you're sticking accidentally into a live electrical box, your tendency is to retract your arm. Very quickly.
But even 120 or 240 volts won't jump across very much air, like, essentially, none.
Compare that to the 100,000+ volts that are carried by the high-tension lines at the top of int[er|ra]state transmission lines -- that's enough voltage to arc across many inches of air without any trouble at all.
So why do we use high voltage at all, why can't we just use low voltage everywhere and be safer?
That's where the magic of the power equation (Power (watts) = Volts * Amps) comes in. But that's for another discussion.
I have watched many YouTube videos. I understand that electricity is electrons moving through a conductor from “+” to “-“ but am at a loss of why they move and why do we have two measurements for one thing.