Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [energy]

Energy is defined as the amount of work that can be performed by a force, measured in joules (J). Energy is power integrated over time; power (W) is energy per second (J/s). This is a poor tag to use. Please consider if your question relates to energy as defined in physics; don't use it as a synonym for power or capacity.

Energy is defined as the amount of work that can be performed by a force, measured in joules (J). Energy is power integrated over time; power (W) is energy per second (J/s).

This is a poor tag to use. Please consider if your question relates to energy as defined in physics; don't use it as a synonym for power or capacity.

502 questions
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Lightning bolt vs. batteries: a coulomb in everyday terms

I am trying to decide if the information on the wikipedia page http://en.wikipedia.org/wiki/Coulomb#In_everyday_terms is reasonable. In particular the statements that a lightning bolt has about 15 coulomb, where a battery has 5000. My first…
kasterma
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Does turning a lighbulb on and off repeatedly use more energy than just leaving it on for hours?

Let's say I have a 60W bulb in a lamp in my bedroom. If I kept the lamp on for 2 hours straight but the next day, I switched it on and off 10 times in intervals of 5 minutes. Which scenario would use more energy?
Christopher Chipps
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Why is an inductor not a good antenna?

[An antenna must have] current flowing along its length, so that the resulting fields radiate that energy into space. (Receiving antennas are just this process in reverse). [This] explains why you can't just stick a small tank circuit on a board…
Phil Frost
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How to compare mAh and Wh

When looking at consumer electronic devices with batteries I sometimes see the battery capacity listed in Wh (watt hours) and sometimes in mAh (milliamp hours). I would like to be able to compare the two different metrics and I'm wondering how to…
Gabriel Southern
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What is the speed of "electricity"?

In a distribution grid, what is the speed of energy signal Is it strictly the same? And how is synchronisation achieved? Is an electric grid essentially an orchestra where everyone is the chief and gives the beat to everyone?
curiousguy
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What's the highest theoretical energy density for a chemical battery?

This is more a physics/chemistry/nanotech question, but what's the theoretical best energy density you could get out of a chemical battery (or fuel cell), if you could arrange atoms in any manner you wanted? I'm thinking of the nanotech batteries…
endolith
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Why are deep cycle batteries rated in amp hours instead of watts hours?

Why are deep cycle batteries rated in amp-hours instead of watt-hours? For example if I see a 85Ah battery, I multiply 85Ah x 12V to get 1020 watts. As household electricity use is measured in watt hours (hence a kill-a-watt) this information seems…
Mauvis Ledford
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Is a microwave's output power proportional to the mass of its contents?

My friend and I are having a heated debate. On the one hand, he thinks that a microwave oven that is empty, consumes almost no power (not considering lights, lcd, etc). He says that once you put an item in the oven, such as a glass of water, the…
Matthew Goulart
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I need the most basic circuit diagram for wireless energy transfer please

I have been all over the net looking for the most basic circuit diagram or instructions to put together a small project on wireless energy transfer. If anyone knows of a good schematic that is super simple and geared towards noobs could you please…
Digital Brent
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Why is it so problematic to have close to zero standby power consumption?

Each electronic device consumes electric power when it is "idle" unless it has a mechanical switch. I can understand that for example a TV with a remote control needs to "be ready" to receive a command from the remote control. But even a cell phone…
sharptooth
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Why is home voltage value higher during the night?

I have been monitoring the voltage in my own home (Mexico 120V 60Hz). I have been graphing the values every minute and I'm starting to notice that during the morning voltage gets up to 127, and during the day (4pm) it can go as low as 118V — why…
GoatZero
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Does this device which claims to reduce reactive energy from a house work?

I've opened a device that states that it can reduce the reactive energy from a house, by plugin it directly to the power outlet/wall socket. I think it is a con, so I've opened it and I saw this black box. Inside this box that I've opened bare…
nemewsys
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In theory, is it possible to make a logic gate that uses zero current?

CMOS greatly reduces the current draw of ICs because one of the complementary FETs is always in the non-conducting mode, so there is only a flow of current during the transition between states, which is just the amount of charge on the gate's…
endolith
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Will repeatedly turning a light bulb on and off damage it?

I have been hearing a common saying that if one keeps switching the lights on and off you will probably damage the light bulb itself, since every time you close the switch there would be a sudden rush of current through the circuit. Given that we…
Derek 朕會功夫
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Why do capacitors have less energy density than batteries?

The basic operating principle of a battery is, in order to charge it, the electrons are removed from cathode and moved to anode by applying voltage. And to discharge, the electrons move from cathode to anode creating an electric current. This…
Hari Kumar
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