The voltage tag has no wiki summary.
8
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8answers
3k views
What is the difference between electric potential, voltage and electromotive force?
This is a confused part ever since I started learning electricity. What is the difference between voltage and electromotive force (emf)? Both of them have the same SI unit, right? I would appreciate ...
7
votes
9answers
762 views
I don't understand what we really mean by voltage drop
This post is my best effort to seek assistance on a topic which is quite vague to me, so that I am struggling to formulate my questions. I hope that someone will be able to figure out what it is I'm ...
6
votes
2answers
264 views
How electric currents can flow between 2 points at the same potential?
According to Ohm's law, if there is a potential difference, $V$, across a resistor then there is a current, $I$, flowing through it.
Since we assume that points along the connecting wire are at the ...
6
votes
2answers
342 views
Voltage and current of positive lightning
For a physics issues investigation I chose to investigate what effects lightning could have on an aeroplane while in flight if it was struck and then go on to discuss some possible implications of ...
4
votes
4answers
368 views
Are square wave really square or are they always relative approximations using harmonics
I'm studying the properties of waves through different mediums, and got hung up on this.
Is a square wave always a sum of harmonics or can we produce a square wave by quickly changing voltage? Is ...
4
votes
3answers
5k views
Why do we use Root Mean Square (RMS) values when talking about AC voltage
What makes it a good idea to use RMS rather than peak values of current and voltage when we talk about or compute with AC signals.
4
votes
6answers
6k views
Difference between current and voltage sources
I am confused about the current and voltage. My intuitive example would be that of a pipe of say water. The diameter of the pipe determines the amount of water flowing per second but the pressure is ...
4
votes
1answer
195 views
why sometimes touching old flickering tube lights starts them properly
In my old house there are two old tube lights. Some times they don't start properly, (specially at evening time, may be it is because of low voltage), they starts flickering i.e. on and off ...
4
votes
2answers
226 views
Why is electric potential scalar?
I can't conceptually visualize why it would be so. Say you have two point charges of equal charge and a point right in the middle of them. The potential of that charge, mathematically, is proportional ...
4
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1answer
121 views
Loopless voltage measurement
I think we are all very well familiarized with the classical voltmeter. Classical voltmeter has two conducting wires that bring two potentials into the box. In the box we have well controlled ...
4
votes
1answer
192 views
What is the mathematics behind artificially generated plasmas via electric fields?
The ionization degree of a plasma is given by the Saha equation, which depends on the temperature and the particle specific ionization energy. In thermal equilibrium, the relation between ionization ...
3
votes
2answers
251 views
How can you have a negative voltage?
How can you have a negative voltage? I don't really understand the concept of negative voltage, how can it exist?
3
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3answers
4k views
Why do birds, sitting on electric wires, not get shocked?
If we would touch electric wires, we would get a shock, even if we are not touching ground (so that no connection is complete form wire to ground through us). I always see that birds sit on electric ...
3
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2answers
142 views
Thought experiment with entangled electrons
Suppose we start out by having two entangled electrons. We separate them by some distance and we put one electron inside a thin loop of wire connected to an extremely sensitive voltage measuring ...
3
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1answer
190 views
Lifetime of battery
If I directly connect two terminals of 3V battery (negative to positive) using copper wire, would it lose all its charge faster compared to another 3V battery that is used to lighten a 1.5V bulb?
3
votes
1answer
449 views
What is the role of battery across a Parallel plate capacitor having equal charge?
Each plate of a parallel plate capacitor has a charge $q$ on it. The capacitor is now connected to a battery. Now, which of the following options are correct?
a) The facing surfaces of the ...
3
votes
2answers
203 views
Electrostatic notion of voltage as it applies to circuits
I have a question that's been bothering me about electric fields, voltage, and circuit analysis.
Initially, I came to understand voltage as it was taught in the context of electrostatics - through ...
3
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6answers
3k views
What causes an electric shock - Current or Voltage?
Though voltage and current are two interdependent physical quantity, I would like to know what gives more "shock" to a person - Voltage or Current? In simple words, will it cause more "electric - ...
2
votes
5answers
436 views
Why doesn't an electron accelerate in a circuit?
Why don't electrons accelerate when a voltage is applied between two points in in a circuit? All the textbooks I've referred conveyed the meaning that when an electron traveled from negative potential ...
2
votes
6answers
311 views
Is voltage electric potential or electric potential difference?
On Wikipedia, voltage is defined to be the electric potential difference. However, I am still not certain as to whether voltage is the electric potential ($PE/q$) or electric potential change ...
2
votes
2answers
700 views
What is the potential difference between point X and point Y?
Here is the problem:
In the above figure I want help on finding the potential difference between X and Y.
It is getting quite confusing due to the battery in the middle. I found the current in both ...
2
votes
1answer
34 views
Question about linacs
Why are the electrodes of a linac connected to an alternating voltage? Within an electrode the electron moves with a constant speed, and once it is outside of the electrode it accelerates uniformly, ...
2
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2answers
555 views
is the voltage drop of a battery that is being short circuited the same as the battery's advertised voltige
So I know this is a pretty fundamental question, but I'll ask it any way. lets say you have a 12V battery, and the positive is connected to the negative directly by a wire with negligible ...
2
votes
1answer
526 views
How does a voltage independent current source work?
So I'm having some trouble understanding what a voltage independent current source is. How can you have a current without a voltage. as I understand it voltage or EMF is the force that drives the ...
2
votes
3answers
4k views
Using A.C or D.C to create an electromagnet
Does it matter if I use A.C or D.C as a source to create an electromagnet? Or Does it depend on the voltage of current?
For example:
I have a coil which has about 50 turns. If I use same amount of ...
2
votes
1answer
148 views
What electric potential is found over individual resistors connected in series to an AC power supply?
Given a set of resistors connected in series to an AC power supply:
What formula governs the peak-to-peak voltage which will be measured when voltage is probed over individual resistors and sets of ...
2
votes
1answer
29 views
Help Understanding Non-conservative Fields
While watching a video lecture I became uncomfortable with the results, which begin around minuite 35. The professor draws an electric circuit with a 1V batter, and two resistors (1ohm and 9 ohms). He ...
2
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1answer
88 views
Which of these two methods is correct for calculating current?
I recently came across a question, for which I saw two possible methods of finding the solution. I was required to calculate the "current flowing" $I$ when given the voltage $V$, frequency $f$, total ...
2
votes
1answer
352 views
Effective resistance of inductor
In a lab experiment, we connected a simple circuit: an AC voltage source, connected (in series) to a variable resistor and an inductor. We measured the current in the circuit, and the voltage that ...
2
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2answers
67 views
Production of electricity from atmosphere
I read the electric field intesity at the surface of earth is 100v/m. Then why can't we keep two metallic sheets at different heights and produce a continuous current by connecting these two sheets ...
2
votes
2answers
730 views
Voltage and Current in transformers
In transformers, the ratio of the voltages equals the ratio of the turns - so double the output coil's turns and the output voltage doubles. Then, in order to conserve energy, current halves.
This ...
2
votes
1answer
311 views
how to calculate electric relative permittivity of fluid or medium
I am confusing in calculating permittivity of the fluid. Permittivity differs from one fluid to another.
$$\varepsilon=\varepsilon_r\varepsilon_0$$
Since it is an electrical property combined with ...
2
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0answers
79 views
How much current would be generated by polarity reversal of Earth's magnetic field?
Continuing from my previous question Is reversal of magnetic polarity in a planet an instantaneous occurence?
A change in magnetic flux is expected to generate an EMF.
In the case where the ...
1
vote
5answers
291 views
How do electrical devices suck electricity?
If the electric potential is 220V and some device needs 1500watts then how does it suck exactly that amount of electrical energy from outlet?
1
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4answers
298 views
Why does it seem that the potential difference dependence of capacitance and total energy stored in a parallel-plate capacitor are contradictory?
Consider a parallel-plate capacitor. Charge is stored physically on electrodes ("plates") which are flat and parallel to one another. If one electrode has charge $+Q$ and the other electrode has ...
1
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2answers
154 views
Highest man-made voltage
What was the highest voltage achieved and was it produced by electrostatic means or just some transformers and multipliers?
What are the limitations when it comes to producing voltage using ...
1
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2answers
171 views
Fundamentality of voltage to current
From Ohm's Law :
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points.
I would like to know if ...
1
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3answers
2k views
Finding current using EMF & internal resistance
What exactly is the difference between internal resistance and resistance?
This came up in the context of a homework problem I have been given:
The circuit shown in the figure contains two ...
1
vote
2answers
296 views
Calculate power $P=V \times I$
I have an adapter which mentions like this...
Input: 100-240V~1.8A
50-60hZ
So how much power does it really consume?
I just knew ...
1
vote
2answers
637 views
Does the 'mAh' rating of a battery have something to do with its power?
I'm curious about the 'mAh' of a battery: how can this impact the power of the battery?
I've done some research on the internet, and most of the articles I found explain about the 'amount of charge ...
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3answers
3k views
How is calculated the potential between two capacitors in series?
Suppose to have two capacitors in series:
The voltage in the middle point will be:
$$
V_X = V_1 \frac{C_1}{C_1+C_2}
$$
How can this be explained? It's been asked in electronics, and explained in ...
1
vote
1answer
103 views
Calculate Capacitance in Series AC Circuits?
I'm supposed to calculate the capacitance of an unknown capacitor in series, but I'm not sure exactly which equation to use.
I know the voltage across the resistor (Vr), voltage across the capacitor ...
1
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1answer
67 views
is it possible to gain from charging cold battery
Is it possible to get higher load of energy into a battery if you charge it when its cold eg. +9C?
the battery is emptier, but does it let the power in?
Is it safe?
1
vote
1answer
72 views
Should the electric potential of a positively charged sphere be negative?
Because the indefinite integral of the electric field results in a negative value? (As the function is proportional to $r^{-2}$?
I've got to be missing something... Help please!! Thanks!
Also, I ...
1
vote
1answer
147 views
What does the current vs voltage graph of a halogen look like?
I have a halogen light with a tungsten filament. It is rated 500w at 130v but I am running it from an inverter in my car that is putting out 110v. I would like to know what the actual power usage of ...
1
vote
1answer
114 views
Electromotive force
EMF is defined as:
"The potential difference across the terminals of a battery or dry cell when it is giving no current to the circuit."
So, if current starts to flow from the ...
1
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1answer
1k views
When does voltage drop occur?
Why or when does it occur in a circuit? What does it imply when you speak of a voltage drop across a resistor? (Obviously, it probably means that the current's voltage before the resistor is higher ...
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0answers
18 views
What works on 8-10 volts, 4 milli amps, and is not hardwired? [closed]
I want to know what is the smallest device that can work on a few milli amps? I know a NE-2 neon bulb works on less than 10 mAmp but on 90 volts at least.
I need to find a small device that:
1- ...
1
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1answer
196 views
What kills you: Voltage or Electric current? [duplicate]
Possible Duplicate:
What causes an electric shock - Current or Voltage?
When someone gets electrocuted, what kills them; a high Voltage or a high Electric current, and why?
1
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2answers
713 views
Basic questions about voltage drop in DC circuit
I understand all the concepts of what voltage is using all the analogies but some things related to the drop of voltage across a circuit confuses me.
If I had a short circuit and attached a ...
