# 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.

375 questions
Filter by
Sorted by
Tagged with
57 views

### 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 ...
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 ...
52 views

### 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(...
101 views

### 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 ...
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 ...
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 ...
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 ...
189 views

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 ...
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.
41 views

### 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, ...
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 ...
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 ...
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 ...
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 ...
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. ...
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 ...
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 ...
936 views

### 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 ...
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 ...
50 views

### 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 ...
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 ...
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 ...
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)\...
13k views

### 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 ...
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 ...