Energy is defined as the amount of work that can be performed by force, measured in Joules. Energy is Power over Time. This is a poor tag to use. Please consider if your question relates to Energy as defined in physics, not as a synonym for Power or capacity.

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0answers
40 views

Determine the 3-dB bandwidth and the 95%-bandwidth [closed]

How do I approach this problem? Determine the 3-dB bandwidth and the 95%-bandwidth of signals f(t) and g(t) with the following energy spectra: I know: ...
-2
votes
1answer
39 views

The bandwidth Ω of a low-pass signal f(t) ↔ F(ω)

I'm not sure about the answers to the two parts of this question: The bandwidth Ω of a low-pass signal f(t) ↔ F(ω) is defined by the constraint: $$ \frac{1}{2\pi } \int_{- \Omega }^{\Omega } ...
0
votes
1answer
60 views

How does the principle of conservation of energy for a phase-shifter transformer apply?

Since the phase shifter transformer is used for regulating the real power in the transmission line by means of changing the angle it leads to the fact that the real power at the secondary side ...
1
vote
0answers
35 views

What happens to the energy bands when a forward bias > Buit-in potential is applied [duplicate]

When we applied a forward bias across a PN junction, the barrier height of the depletion region reduces. What will happen to the energy bands when we apply the forward bias greater that the built-in ...
2
votes
1answer
41 views

Dynamic energy and dynamic power in microprocessors

In a class I'm learning about dynamic energy and dynamic power and the notes seem to be incomplete. ...
0
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1answer
69 views

Charging of Cell Phone Batteries and Electricity! [closed]

Does charging an already charged battery of cell phones/laptops consume electricity? Whenever my cell phone becomes fully charged while charging, it asks me to remove the charger from the socket to ...
0
votes
2answers
36 views

Energy meter design/mcp390x

I am considering the mcp390Xa series for a energy meter project. What I am not understanding here is where the voltage part of the watt calculation is happening. Is this up to the micro to measure ...
2
votes
1answer
101 views

Extracting the Most Energy From a Capacitor

I have a 5V super capacitor which I'm trying to extract the most energy from in the most efficient way possible. This capacitor is tied to the input of some regulator (which is the question of this ...
0
votes
0answers
38 views

Measuring consumed energy with MCP3905A

first of all sorry for my English because I'm Italian. I'm trying to measure consumed energy with MCP3905A evaluation borad. ...
1
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2answers
85 views

Ohm's Law vs. Conservation of Energy Misunderstanding

I am currently misunderstanding the relation between Ohm's Law and the law for conservation of energy. I am referring to the example (in the book "Foundations of Analog and Digital Electronic ...
5
votes
3answers
363 views

How long can I practically power an IC with a capacitor?

If I have, for example, an IC that draws 10mA @ 3.3V, how large of a capacitor would I need to power it for 2 minutes? 5 minutes? I understand that using capacitors to power an IC is not the most ...
2
votes
6answers
267 views

Difference between Voltage source and Current source?

So what's the difference between a Voltage source and a Current source? Aren't they the same? Because after all they are related with the formula \$V = IR\$. So it means that If we produce a voltage, ...
0
votes
2answers
140 views

connecting two capacitors in parallel

two capacitors are paralle connected with an open switch. both have diffrent capacity in which: $$c_1>c_2$$ and both charged with diffrent voltage $$v_1\neq v_2$$ and now we close the switch. ...
3
votes
4answers
208 views

does real and reactive energy exist

Are there any such things as real and reactive energies just like real and reactive power ? if so how is reactive energy dissipated?
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votes
3answers
53 views

Energy of a signal [closed]

In signal analysis we work out the energy of a signal. We get a number and thats the end of the story, but theres no explanation of what it means in practise. If it was just some abstract mathematical ...
0
votes
2answers
138 views

3-phase energy meter with CTs

I need to measure 3-phases. Usually I would use CTs on the differential port on a LTC1966, then connect Vout+ to an ADC port on a uC. I do that on a 1-phase application. The problem is now, that we ...
3
votes
1answer
417 views

Logging measurements from an analog Gas Meter

I want to capture a gasmeter counter to log the gas consumption in my database. Problem: till now I did not find a way to read the meter. I tried a sensitive hall sensor that could react on the ...
2
votes
2answers
577 views

Arduino: How can one control a 2-wire DC motor with PWM?

I want to control the speed of a two-wire DC motor using PWM. I already managed to control a 4-wire motor, but now I need to use a two-wire motor. I would connect it to the Arduino directly, but the ...
-1
votes
2answers
93 views

How long should I leave the light on? [closed]

I'm not sure if this qualifies as electrical engineering, but I remember my old physics teacher at school saying that if you switch a light on in a room and you're planning to return relatively ...
0
votes
3answers
132 views

Is the energy flow due to a an alternating current constant or cyclic

I understand that the Poynting vector shows us that energy flows in the region outside, or between, conductors, but the maths gets too deep for me to discover, when the current is alternating, whether ...
0
votes
0answers
185 views

Calculating true power/energy usage from battery on smartphone?

I am having some problem to calculate power consumption from android smartphone... First my setup: Android smartphone is connected to PC with USB. Both smartphone and USB do not provide their own ...
1
vote
0answers
91 views

When a smartphone is connected to a charger (USB), does it use battery or charger as it's main power supply? [closed]

When a smartphone (fully charged) is connected via USB to PC (or to charger) does it uses charger or it's own battery as main power supply? Battery is supplying about 3.8-4.1 V and USB ~5V.
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votes
1answer
163 views

Typical Power circuit for smartphones? Correct energy measurement? (Nexus 4, iPhone.. etc)

I am trying to perform some energy measurements using smartphone. And to make sure that I am performing my calculations correctly, I been trying to find any examples of typical power circuit in ...
6
votes
2answers
297 views

Where does all the power consumed by a CPU go?

Where does all the power consumption of a CPU go? Does all the power drawn by the PC's CPU get transformed into heat? Or does it get transformed into part heat and part some other kind of energy?
7
votes
3answers
497 views

Does higher resolution of LCD/LED display mean higher energy consumption for the very same matrix size

If two mobile devices being compared have exactly the same LCD/LED screen (matrix) size and exactly the same battery, will the one with higher resolution have higher battery consumption and thus will ...
2
votes
2answers
74 views

charge extraction from solar cells in low light conditions

This is probably not that deep a question, but how can one extract power from panels in low light? A 6V panel would dip to ~2V or so, and power output would sink lower. In conventional systems, how is ...
-2
votes
1answer
66 views

power source unit for two devices

I have two boards that need 2.5A each and 12V for input. I do have a cable to split the DC, like this one ...
0
votes
2answers
76 views

Kilowatt hour from Complex power

How can I calculate Kilowatt Hours from: Complex Power = 1,5 kVA Electrical current consumption = 10 A It's three-phase electric power.
2
votes
1answer
131 views

Finding the total energy of the network in steady state

i got a network below in steady state im trying to find the energy in the network by the capacitors and inductors. simulate this circuit – Schematic created using CircuitLab My attempt ...
18
votes
1answer
584 views

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 ...
2
votes
0answers
217 views

How calculate three phase kilowatt hour from time sampled data of voltage and current of each phase

My problem is I want to calculate three phase kilo watt hour from time sampled data of current and voltages. My doubts 1) How can I calculate the kilowatt hour from time sampled data? Is it any ...
4
votes
1answer
111 views

Kilowatt Hour Definition

This is a very simple question but something that I'm not able to wrap my head around. This Energy report states generated electricity. But what does "generated killowatthours" mean? I know that ...
1
vote
2answers
148 views

What happens to the circuit Voltage, Energy?

I was recently asked this question to calculate the voltage across a capacitor. The problem is described as follows :- Consider a capacitor "C" connected across a voltage source "V". Once the ...
17
votes
6answers
1k views

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 ...
3
votes
2answers
252 views

Is the energy loss in a voltage drop equal to heat/mechanical work/light emitted?

I am wondering if the energy loss in a voltage drop over an entire circuit is equal to the energy transferred from the circuit (e.g. light/sound/mechanical energy/heat). If this is true, wouldn't ...
1
vote
1answer
116 views

Does shutting down and repowering CPU consume more energy?

I have an internetshop that has 20 CPUs. Only 50% on average are being used throughout a regular day and almost 80-100% during saturdays. I use a Server-Client to Shutdown an unused computer but ...
39
votes
6answers
8k views

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 ...
2
votes
1answer
3k views

Confusion between MW and MWh

A 1MW power plant producing power constantly for 24 hours will produce 24 MWh a day. Is that right? If it is, I don't understand when it says, in ...
2
votes
2answers
194 views

How is energy consumed in a PN junction?

In the schematic above, there's a PN junction with a source \$V_d\$, the barrier potential \$V_J\$, contact potentials \$aV_{J0}\$ on the P-side and (1-a)\$V_{J0}\$ on the N-side. \$V_{J0}\$ ...
1
vote
4answers
122 views

Looking for a better understanding of a kilowatt hour and trying to size an electricity supplier using it

I am trying to design a fuel cell that can provide enough energy for 1 day's use a maximum capacity but I am having trouble sizing the fuel cell because I need a better understanding of kilowatt ...
3
votes
1answer
183 views

ARD00280 Microchip Energy Reference Schematic Live and Neutral Swapped?

Looking at the Microchip Energy Chip reference design I noticed that the power is being sampled from neutral. My first reaction to this was this is backwards, that the power should be sampled from ...
1
vote
1answer
123 views

Power and energy measurment for embedded system -help needed

I am trying to measure the power consumption of a low power embedded system. As the embedded system consumes current in random pulses from the battery pack, I am using an oscilloscope to analyze the ...
-1
votes
1answer
376 views

Can we generate enough electricity to light up street lights by means of a dynamo being rotated by car wheels?

I often wonder if we can place an efficient dynamo underground on a fast moving highway (where traffic flow rarely stops). The dynamo is mechanically rotated and generate electricity to lightup the ...
6
votes
3answers
419 views

Electricity consumption of electrical machines - why do they consume electricity when they are not turned on?

The question is, why do electrical machines consume power when they are not turned on (they are plugged into an outlet)? Also, suppose there is a seven-port USB hub with AC power. Is the power ...
2
votes
3answers
398 views

Energy conversion from Electrical to Mechanical

I have a requirement where I have to design a very small device capable of pulling in and out a small piston through a feedback.I know it can be done using motor but AFAIK I need higher voltage and ...
18
votes
1answer
12k views

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 ...
8
votes
2answers
6k views

Is it possible to use Kinetic energy to power small devices?

I've tried looking around for as much information as I could gather to build really small wearable electronics that could power themselves by generating energy with movement. I know that the ...
3
votes
1answer
210 views

What is the energy efficiency between FM radio tower broadcasting over an area vs point to point streaming via Internet?

Doing some research, it seems that an FM radio tower in a densely popoulated area can maximally transmit about 50kW of power. If you assume a certain amount of people tuning into the station, is that ...
4
votes
2answers
4k views

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 ...
3
votes
2answers
275 views

How efficient are micro turbines in generating efficent energy? [closed]

Would one large wind turbine be more efficient than many small wind turbines in theory?