101 votes
Accepted

Why don't electrons take the shorter path in coils?

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 ...
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  • 2,170
55 votes

Why is electricity consumption billed in watts and not amperes?

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 ...
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  • 40.9k
43 votes
Accepted

Does coiling and straightening a wire change its resistance?

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 ...
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  • 121k
41 votes

Why do computer graphic cards use 8 pin (4 positive and 4 negative wires) connector instead of connector with only single positive and negative wire?

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. ...
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  • 144k
40 votes

Why is the neutral pin hotter than the live pin?

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 ...
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40 votes

Will using a resistor in series with a LED to control its voltage increase the total energy expenditure?

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 ...
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  • 59.7k
38 votes
Accepted

Why is electricity consumption billed in watts and not amperes?

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 ...
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  • 389k
36 votes

Why can I use P = I²R but not P=V²/R when calculating energy lost in a circuit?

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 ...
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36 votes

Am I compensated by the electricity company for electricity that exits my home on the neutral wire?

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 ...
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  • 1,998
34 votes
Accepted

Why can the regenerative brakes of the Oslo Metro only share energy with other trains if they are "nearby"?

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 ...
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  • 161k
33 votes
Accepted

Why can I use P = I²R but not P=V²/R when calculating energy lost in a circuit?

60A through a 0.01ohm resistance gives a 600mV drop. That is the voltage you need to use in the equation.
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31 votes
Accepted

Why is there no net current in a wire without a voltage applied?

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 ...
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29 votes

Why can the regenerative brakes of the Oslo Metro only share energy with other trains if they are "nearby"?

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 ...
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  • 801
29 votes
Accepted

Could transporting electricity using plastic water pipes be feasible?

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 ...
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29 votes

What is the speed of "electricity"?

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 ...
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  • 48.3k
27 votes

Why can the regenerative brakes of the Oslo Metro only share energy with other trains if they are "nearby"?

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, ...
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25 votes
Accepted

Why are circuits considered loops?

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 ...
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  • 12.5k
25 votes

How much power does a cell phone charger actually use?

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 ...
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  • 7,684
25 votes
Accepted

What is negative current?

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 ...
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  • 14.1k
23 votes

What is the best way to convert a 10V power supply into a 5V power supply?

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, ...
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22 votes

How to stop plastic granules sticking to the iron wall of their silo?

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.
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22 votes

Why do batteries only have resistance one way?

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 ...
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22 votes

Why is the neutral pin hotter than the live pin?

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. ...
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  • 144k
22 votes

Where exactly does the power company cut my power when I fail to pay my electric bill?

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 ...
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  • 3,923
22 votes

How have my neighbours’ appliances been damaged?

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 ...
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  • 15k
21 votes

Why is there no net current in a wire without a voltage applied?

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 ...
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  • 10.5k
20 votes

How can electricity be positive when electrons are negative?

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 ...
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  • 48.3k
19 votes

If electrons move slowly in an electrical circuit then what signal or energy is it that travels at the speed of light?

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 ...
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  • 1,066

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