Questions tagged [energy]

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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If greater potential energy is toward pos charge, then why PN energy band diagram show lower energy toward pos charge across depletion region?

If in an electric field, greater potential energy and voltage are toward the positive charge and away from negative charge, then why do PN energy band diagrams indicate lower energies toward the ...
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69 views

Power calculation

Let's say I'm gonna charge a 1mF capacitor from 0 to 100V in 10 seconds. Assuming there's no limiting resistor nor any other losses, the total energy that must be tranfered from the 100VDC supply to ...
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Derivation of energy in capacitor

While searching for something totally unrelated to this, I came a cross a website that derived it in this fashion: the instanteous power in a capacitor is given by $$p_c= v_c(t)\cdot i_c$$ since $$i_c(...
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Power factor improvement [closed]

There are 3 resistive bulbs (60 watts each) in series fed by 230Vrms from the transformer. If I apply capacitors in parallel with load I will get more Voltage. The more capacitors, the higher the ...
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48 views

Power factor down after solar connection

We installed solar plant in factory. After that power factor goes down to 0.16. Normally it never goes below 0.85 in history even if we keep APFC off. We always maintained it to 0.99. Note - Main ...
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1answer
40 views

Difference in electrotherapy Lifepak 12 [closed]

I'm a beginner medicine student and I've got a question out of curiosity, why in defibrillators lifepak 12 or other versions..paramedics or dictors set energy for defibrillation and cardioversion in ...
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1answer
86 views

How does a relay or switch work with batteries or capacitors?

I am charging my capacitor so it can act as a battery for a short period of time. I already did the calculations for the battery discharging and charging. My problem is now that I have a load, I want ...
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3answers
189 views

What is reactive energy?

We know the typical equation for instantaneous power (which can be proven): \$p(t)=v(t)i(t)\$. In sinusoidal steady state (let's ignore harmonics for simplicity), \$v(t)=\sqrt{2} V_{\text{rms}} \cos{(\...
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Is this scenario an efficient way of generating electricity?

I will try my best in order to provide information which could help you imagine the scenario. Accurate results are not compulsory. I am generating electricity using a 5kW alternator but for the ...
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How to calculate Energy Readings in DALI-2?

I'm reading the memory bank202 from a DALI-2 supported led luminary for energy consumption. When the lamp is on, I see that memory bank location 9 and 10 is increasing. But I couldn't understand how ...
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1answer
69 views

Understanding relation between energy use, watts and amps

I'm looking into air conditioners and I've been unable to fully understand the relation between watts, amps and the energy ratings (in this case, the one used in the United States, the yellow Energy ...
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Fast method to calc th Fourier transform

exist a fast method to calc the Fourier trasform (in both sense, t -> f and f->t)? When I use the table and the properties of the Fourier transform, sometime I have difficult to calc this... Any help ...
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Power calculation help

I have a hardware setup that provides me with power being consumed every second so I get somewhat of a different reading every second. Using these per second readings how do I calculate kwH?
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54 views

Capacitor's energy required for a predetermined drop in its voltage - with LDO and constant current elements as load

I am trying to understand how much energy a circuit (composed by some passives here called analog, and an MCU) will require. The system is powered through a capacitor, and the "passives" are actually ...
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27 views

Battery Ah specs vs actual Wh when charging and discharging

It is ubiquotously stated that Wh = Ah x V. While this is true (at least regarding the units) I have some doubts about the practical aspects of it. Using an example: Let's take a fully discharged (0%...
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4answers
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Energy Transport in Circuits

I've been reading about how energy is actually transported in circuits (I first read about it here: http://amasci.com/miscon/ener1.html). The description in this article of why electrons don't move ...
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1answer
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How do we have the \$E=\frac{1}{2}L_1I_1^2+\frac{1}{2}L_2I_2^2 \pm MI_1I_2\$? Can anyone show me its proof?

What is the total energy that two inductors store? Solution \$R_{th}=(12||6)+6=10Ω\$,so \$I=\frac{90}{10}=9,I_1=9\times \frac{6}{12+6}=3,I_2=9\times \frac{12}{12+6}=9\$. So the energy that two ...
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1answer
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Capacitor charging and energy

Assume I have a capacitor with capacity \$C\$ and is charged to a voltage level \$V_a\$ and then discharged. 1) During discharge it dissipates \$E\$ joules of energy. What is the equation to find ...
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1answer
96 views

Voltage without amps [closed]

I have just read an article on electricity extracted from the atmosphere. Apparently there is a massive supply of collectible voltage available from the air. However the amps available is very low. ...
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2answers
96 views

Might an x-ray tube have the capability produce more power than it consumes?

In transformers, when the voltage is powered up, the current is proportionally powered down. In the x-ray tube’s transformer, this also happens. However, the current of an x-ray tube is not the ...
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1answer
33 views

Interfacing Arduino for variable power supply

I'm a mechanical engineering student with no knowledge on Arduino microcontroller. I am currently working on a project of using Artificial Neural Network in a hybrid solar heating system. The hybrid ...
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41 views

Calculate time energy is stored in capacitor

I have this problem: I've calculated A) to be 8 nJ, and my Vc(0) = 4 V and Vc(∞) = 0 V. I tried using the wc(t) = 1/2CVc^2 formula to calculate the time when the energy of the capacitor is 1 nJ. ...
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The method and calculation for the total energy that two inductors,which has Mutual inductance, stored in this circuit

The solution for the total energy that two inductors stored in this circuit is \$E=\frac{1}{2}\times 4 \times 3^2+\frac{1}{2}\times 6 \times 6^2-1\times 3 \times 6=108J\$ I want to ask two things ...
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Free-as-in-beer power from neutral and ground?

I live in a house where each socket has 3 connections,: hot (phase) neutral ground Where: The voltage between hot and neutral is about 220V AC. The voltage between ground and neutral is about 2-3V ...
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1answer
34 views

Does the size of switch-mode adapters affect their efficiency?

I know that a rule of thumb to judge the efficiency of a traditional iron core transformer is to look at its size: the larger it is, the higher the number of windings, the larger the core, the ticker ...
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46 views

How to determine electrical energy and the convert it to heat?

I've been stuck on a problem for quite some time now. I really cannot get my head around it. It's been a while for me, and I just recently been taking up a class again in electrical engineering. I've ...
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1answer
43 views

Energy subtracted from a capacitor for a given voltage drop

I am trying to estimate, from a total energy of a capacitor (which is the output of a charge pump circuitry), how much energy do I have to power up an LED before the voltage goes below a certain ...
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2answers
49 views

How turn off lights automatically?

I am trying to make system where I want lights to turn off automatically. It should work like that if someone kept lights on by mistake then it should turn off automatically without any human ...
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1answer
42 views

Calculating Energy Consumption Using a Current Sensor and Voltage Sensor

I'm creating a PCBA that uses a hall-effect sensor to measure current and a transformer rectifier design to measure the mains voltage. The voltage is 110-240 V, ~60 Hz. I wrote a digital filter and ...
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2answers
101 views

How do I know if a current source supplies or receive energy?

In example, I have this circuit: I know that in a current source if the polarty is \$-\rightarrow +\$ it supplies energy to the circuit, but how I can determinate the polarity in this case (of \$I_{...
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4answers
93 views

How much energy is stored in the capacitor after 18us?

I have the following problem: Consider the circuit below The graph shows the current through a \$50 uF\$ capacitor. The initial voltage across the capacitor is \$V_0=10V\$. How much energy is stored ...
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53 views

Are there any instruments that can be used to measure the stored energy across a capacitor?

Apologies if this a noob question but I was wondering if there was a way I could directly measure the energy across a capacitor in Multisim so that I can compare it with my analytical result.
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Where in AC the charge gets its energy again?

I'm quite new to electronics. Most of the tutorials I've watched are DC oriented and it's pretty clear that there's a voltage drop across the DC circuit. When current flows through components in DC, ...
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2answers
64 views

Calculating the intensity of an electromagnetic wave

I’m a bit confused when it comes to calculating intensity versus energy of a wave. If I’m given an electronmagnetic wave with an energy of 1 eV, how do I calculate its intensity ? I know intensity is ...
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2answers
36 views

Calculating Phase wise Energy in Three Phase System

In three phase three wire system, is it necessary to calculate phase wise energy? As per my knowledge, in three phase three wire system we are concerned about only total power/energy. But does it ...
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1answer
118 views

Difficulties with capacitor circuit analysis

I have been given this question by one of my lecturers and have been having difficulty with it. I was wondering if anyone could help me. In the circuit of Fig. 1, switch SW1 has been closed, and ...
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2answers
119 views

Role of the neutral conductor in three phase systems

In a symmetrical and balanced three phase system no current flows on the neutral conductor. Obviously the real electric power distribution systems are not perfectly balanced, so there is a current on ...
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3answers
48 views

Hypothetically, 6 or more phase line with same mechanical energy?

So I don't understand a concept of mechanical to electrical energy conversion. Let's assume I have a 3-phase generator and need X amount of mechanical power in order to get 200 Volts Phase-Neutral. ...
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2answers
1k views

How many watts does a 40 MHz radio frequency signal create?

I am new to the study of electromagnetic frequencies and electrical engineering as a whole. I am trying to understand how to convert a radio frequency into energy, or calculate the power density of ...
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1answer
74 views

voltage potential energy clearance?

1 coulomb = charge of 6241509074460762607.776 protons(fixed amount of energy passing thru certain point). So 1 volt = 1 joule(energy) per 1 coulomb. and 2 volts = 2 joule(energy) per 1 coulomb. does ...
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4answers
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A passive sensor does not need any additional energy source?

I am currently studying the textbook Handbook of Modern Sensors - Physics, Designs, and Applications, fifth edition, by Jacob Fraden. In this textbook, the author states the following: All sensors ...
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1answer
41 views

Energy dissipation of a resistor in an AC circuit

I am given a resistor of known resistance with a sinusoidal voltage across it, and am asked to calculate the energy dissipation between t=0 and t=1. Not sure how to do it. Would I Use P=V^2/R and ...
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Design of a 5kW residential Solar system with battery- need help with electrcial diagram

A design project asks for a design proposal of 5kW solar panel with inverter and battery system for a residential house. I have completed the energy estimation, panel size, orientation, and selected ...
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1answer
23 views

Using solar to recharge a Li-po battery

I'm looking for help determining what size of solar (PV) I should use to recharge my Li-po battery after discharged. Battery Characteristics :Capacity:1600mAh Nominal Voltage: 3.7V Charging ...
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4answers
79 views

How does energy dissipates in a purely reactive circuit?

Suppose in a home, power factor drops to zero. It means that the circuit becomes purely inductive. If the energy meter is connected at incoming power supply point,will the energy meter still keep on ...
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1answer
50 views

Why is my equation for getting the energy of a capacitor wrong?

I have a question. Because \$Q=CV\$, \$U=VIt\$ and \$Q=It\$ The energy in joules of a capacitor from what I get is \$U=QV\$ with \$U=C(V^2)\$ But why when I see on the internet it is \$U=(C/2)(V^2)\...
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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 ...
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3answers
518 views

Producers consumers balance in the grid

In a large distribution grid, it is said that consumers and producers must be in balance; what that means physically, in correct (not simplistic) mathematical formulation, is not clear: perfect ...
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3answers
156 views

Dissipation and Impedance

it is known that power losses (which become heat) in circuits are due to resistances, because of Joule Effect. But sometimes I read that dissipation is due to the real part of a certain impedance, and ...
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Energy dissipation in a circuit with only capacitors [duplicate]

Context: Consider a circuit with only two linear time invariant capacitors. If I charge one the capacitors and then throw a switch that closes the circuit, there will be some redistribution of charge. ...

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