100
This type of wire, used for making coils, is commonly called "magnet wire". https://en.wikipedia.org/wiki/Magnet_wire
It looks like it's bare copper, but it's actually coated with a very thin layer of transparent insulation. Otherwise, you're absolutely right -- if the wire were really bare, the coil wouldn't work because the current could cut straight ...
60
You are not really paying for the electrons that move in the wire, you pay for the force that moves them. It is like cutting a board with a hand saw. You push an pull it to cut the wood using the same teeth for each stroke. The electric company pushes and pulls the electrons and the moving electrons do useful things like provide light. You furnish all of the ...
54
They don’t bill in watts (power) either. They bill in watt-hours, that is, energy consumed. (kilowatt-hours typically.)
Let’s break this down a bit. Current alone doesn’t tell you power. You also need to know the voltage, as power is voltage * current. Then, you tally power over time to figure energy.
Now you could estimate power from current if you make ...
44
I wanted to know first off why the coils are coiled?
Suppose the wire is 10 m long. If you don't coil it, some of the heat it produces is "here" and some of the heat is 10 m away. Coiling it means you can heat a small area instead a long skinny area 10 m long.
when the coils are stretched too far apart thy run cold and when they are close together the ...
41
This allows multiple cheap connectors and wires to be used, instead of single thick wires and more expensive high current connectors. Multiple thin wires are also more flexible than thick wires. Multiple pins on the circuit board ease the problem of tracking high currents on a PCB.
It's not just about power handling, it's the voltage drop on the cable that ...
39
I just had one of those last week. The plug was hot, and the socket was hotter. I'm the electrical guy so I popped it off. #12 stranded wire shoved into a smaller #14 backstab hole. Two thirds of the strands had missed the hole!
Dumb things like that happen all the time, and you have to nip 'em in the bud the moment you see them.
Don't use this ...
39
You've got the right idea. Partly.
An LED used with a series resistor does waste the energy dissipated in the resistor. Depending on the voltage from the power supply, you can easily waste more energy in the resistor than you use for the LED.
So far, you are correct.
What I want to correct is the idea that the resistor is there to lower the voltage.
...
38
Why would companies bill for wattage instead of amperes?
Because amperes don't tell the full story about energy transfer from a source to a load. If you supplied a load that took 100 amperes at 1 volt, the power consumption (joules of energy per second) is 100 watts. If a different load took 100 amperes at 100 volts, the energy transfer per second is 10,000 ...
36
The problem assumes you understand something that is not clearly spelled out: the wires and the (unknown) load are in series. Therefore they share the current, not the voltage of the battery.
That's the situation:
simulate this circuit – Schematic created using CircuitLab
As other have pointed out, the voltage drop across the wires is small given ...
answered Dec 8 '16 at 7:04
Lorenzo Donati -- Codidact.com
19.5k4 gold badges48 silver badges87 bronze badges
36
There isn't really any such thing as "electricity". The word "electricity" simply refers to the transmission of electrical energy, by using the motion of electrical charge.
Electrical energy and electrical charge are not the same thing. In particular, electrical charge is not scarce or valuable; all matter contains electric charge, and, in fact, it all ...
34
Is the resistance in the wires along the track making it not worth it?
That will be one factor. The article states that each set has 12 x 140 kW motors giving a total of 1680 kW (1.68 MW) for each train set. The system is 750 V DC and, unusually, uses third-rail in some sections and overhead lines in others. At those power levels currents in the order of ...
33
60A through a 0.01ohm resistance gives a 600mV drop. That is the voltage you need to use in the equation.
answered Dec 8 '16 at 5:46
Ignacio Vazquez-Abrams
46.9k2 gold badges68 silver badges95 bronze badges
30
Statistically, there are as many electrons moving in one direction as there are in the 180º opposite so there is effectively no net current. What we know as "current" is the movement of more electrons in one direction than all the others (1D, 2D or 3D through a piece of metal). That's how you can have "tons of free electrons" but no net currents flowing or ...
29
For obvious reasons, any railway network is divided into isolated sections and each of those is powered separately from the medium or high voltage grid through its own transformer, circuit breaker and switch.
Two trains within the same section can share power directly. Trains in different sections can only do so through the grid. Since the Oslo Metro uses ...
29
Water, especially pure water, is a rather poor conductor of electricity. 5–50 mS/m for tap water vs. more like 6E+7 S/m for copper. That's about 10 orders of magnitude, so for the same losses as a 4 mm diameter AWG 6 wire your pipe would have to be 16,000 km in diameter, which would make plumbing somewhat inconvenient. You'd need a return conductor too.
...
29
For most of the copper wire and traces you see, about 60% the speed of light in a vacuum. The energy is the signal so they are the same.
The speed of electrons is much slower...slower than walking pace. The electrons aren't moving to and from the powerplant 60 times per second.
Think the difference between the speed of sound and the wind. The wave (energy) ...
27
Electric railway guy here.
Long distance propagation
I have seen 600V trolley wire dip to only 200V four miles from the substation under heavy ~300A load from a single articulated car. (4/0 wire, 107 mm2, rails as return).
Third rails are a great deal beefier, but subway trains are a great deal heavier. Typically third rail shoes are fused at 400 amps (...
25
Most circuits are considered loops because charge in conductive materials tends to equalize electrostatic potential differences relatively quickly. Take a long wire/rod for instance. Let's say you can add electrons to one side of it. At first you start with 0 electrons. When you add the first electron, there's nothing else around so it can go basically ...
25
understand that voltage is relative to ground,
I prefer to disagree. A voltage is against a reference point. Often that reference point is ground but not always.
Taken the above into account your current is defined the same way.
Take a pin/port of a component or circuit. You can now define the current going into that port/pin as positive from which it ...
23
The input numbers are a maximum or worst case scenario that the manufacturer wants you to take into consideration, they do not reflect the power draw at 100% of the time. It could be for example, some surge current when first plugging it in due to capacitors charging up, or just some huge margin.
Also, the average input current at 100V would be more than ...
23
If you want to convert the voltage to 5 volts, you should not use a resistance-voltage divider. That way you will indeed create 5 volts, but as soon as you apply a load the voltage will drop.
Instead, you have two options in general to regulate voltage. The first option using a linear regulator, and the second option is using a switch-mode power supply.
...
22
If your plastic pellets are getting charged, you can flood the inside of the silo with ionized air using a commercial generator. These are not uncommon in the plastics industry.
22
Why do batteries only have resistance one way?
They don't.
To a first approximation, a battery is a voltage source in series with a resistor.
Your wrong impression is probably due to invalid measuring. You can't just connect an ohmmeter across a battery. Most ohmmeters aren't designed to measure resistance with a voltage source in series. That will ...
22
I only have a somewhat vague understanding how the electrical grid works. I know the basics of energy production, and that the electricity comes to our homes using power lines resting upon those big supports we see everywhere. I would imagine the grid somehow splits into smaller sections like a tree whose endpoints are the final destinations, such as single ...
22
A broken neutral can cause serious over-voltages on an electricity supply.
UK supplies are usually three-phase and neutral, with approximately 415V between phases, and 240V between any one phase and neutral. The secondary of the substation is "star" wound, with the neutral being the common point. Most UK houses are supplied from one of the phases, plus ...
20
The voltage on each pin, live or neutral, is irrelevant. Also the current flowing through each pin will be the same.
The difference is the resistance of the connection the current is flowing through. This will be caused by the springs in the socket not making good contact with the plug pin.
It's not unusual for heavy current users like kettles to make the ...
20
First before answering what I think is truly your question, I will have to beat into you how voltage are relative:
An atom has protons in the nucleus which is orbited by electrons. If the numbers are equal, then the positive and negative charges cancel out and the charge is zero.
Suppose we start with two terminals. Each terminal has a net charge of zero ...
19
Short answer: some textbooks are infected with a misconception, the idea that electrons always orbit the individual metal atoms. Nope. They'll also tell you that electrons only jump between atoms when a voltage is applied along the wires. Wrong.
In metals, the outer electron(s) of each metal atom have left their original atom. This happens when the ...
19
It is changes in the fields inside and around the wire that travel at the speed of light. Imagine the wire as a hollow tube full of electrons. When there is no current the electrons are all sitting there, repelling each other, but since there is nowhere to go, they just sit still.
When an electron at the back of the wire starts getting pushed (by a battery ...
Only top voted, non community-wiki answers of a minimum length are eligible
