The study of the presence and flow of electric charge. Charges, currents, fields, potentials.

learn more… | top users | synonyms

0
votes
1answer
46 views

Basic concepts on Electricity [on hold]

How do electrons move? I mean really do they move? I read that they move in circular shells AROUND THE NUCLEUS. How can they move in the conductor? I have read that there are valent electrons that ...
2
votes
1answer
22 views

Why is the electric field highest in regions of highest resistance?

I know Kirchhoff's law and that current must be constant. But what exactly is the phenomenon, from first principles, that causes the electric field to be stronger in a region with lower carrier ...
6
votes
2answers
638 views

How exactly does a solar flare cause a power line surge?

There are occasional large scale electrical blackouts caused by solar flares. Quebec Solar Flare Blackout My question is: what affects the severity of the problem? It obviously depends on the ...
1
vote
2answers
26 views

Quality Factor in a Parallel LC Circuit

I was wondering if there is a notion of a quality factor in a parallel LC circuit, since there is no resistance. One can show that this circuit has a resonance frequency as follows: Impedance: ...
39
votes
3answers
5k views

Why do electric sparks appear blue/purple?

Electric sparks tend to appear blue or purple or white in color. Why?
1
vote
1answer
43 views

What actually happens when electrons 'collide' with other electrons in a conductor to produce heat in an electrical circuit?

Textbooks describe resistance as involving electrons colliding with other ions in metals, resulting in a heating effect, though how exactly is this achieved? Although I am not required to learn the ...
2
votes
2answers
109 views

Does “ac current” mean that the electricity goes left and right or just changes polarity?

AC goes one way in one phase and the opposite way in the other phase, but is going right and to left, or is it only changing the polarity from (-) to (+)? If light bulbs turn off and on (so fast we ...
0
votes
0answers
16 views

Relation of current with frequency and voltage [closed]

I tried to solve a numerical problem but I got stuck and I think it very necessary I will drwa certain basic conclusions when I would found its solution. The question is: An incandescent lamp ...
0
votes
0answers
13 views

Calculating work needed to move a charge between plates of an uncharged capacitor [closed]

My first guess was zero work because there's no electric field(I think). E.g. a parallel-plate capacitor $4.9 cm$ on a side, spaced $1.0mm$. The work needed to move $6.8\mu C$ seems to be $1.1J$ And ...
0
votes
2answers
18 views

Why can insulators be charged by friction but not by conduction?

When you charge an insulator by friction, the close contact of two electron clouds (each from a different medium) allows for electrons to be transferred between them. Yet why can the same not be ...
0
votes
0answers
8 views

rectifiers physics fundamental of electronic devices [closed]

What value of filter capacitor is required to produce a 1% ripple factor for a full-wave rectifier having a load resistance of 1.5 k"ohms"? Assume the rectifier produces a peak output of 18 V.
1
vote
3answers
23 views

What does it mean when we say that power of a bulb is 10 W? Since $V/I=$ resistance is a constant, how can power $=VI$ be a constant?

My question is simple. In Ideal situation, at constant temperature, we know that normal appliances like a filament bulb has straight Voltage vs Current graph, meaning its resistance is constant or ...
0
votes
0answers
17 views

Is there any good book about the history of electricity? [closed]

Is there any good book about the history of electricity? Electricity history starting from William Gilbert in the 17th century.
0
votes
2answers
47 views

Potential difference inside charge distributions

Always when I think about potential difference inside a symmetrical charge distribution, I think of it being equal to zero because it's dependent on the field and I imagine the directions of each of ...
1
vote
1answer
35 views

Understanding electric field and potential inside an half-connected wire

Let's say we have a 9 V battery and a wire as shown in the image below: Let's assume H is the reference for measuring potential. I know the potential in F is 9 V, and I know the electric field in F ...
1
vote
1answer
37 views

Why did the electric potential energy fall in this situation?

Suppose you have two capacitors configured as shown in the image below. One of them has charge $q$ and the other one is uncharged. Then, you close the switch, allowing charges to flow. After ...
0
votes
4answers
134 views
1
vote
2answers
45 views

Electric field on the surface of a charged sphere

We know that the electric field for a point charge is $$ E = \frac{KQ}{R^2}. $$ If $R$, i.e. distance from the electric field producer to the point where we want to find the electric field becomes ...
3
votes
1answer
39 views

Why does lightning generate multiple branches?

Everyone have seen how lightning occurs. But then I realized that lightning never occurs in straight lines but it follows branching. Why is that so ? Why can't lightning goes in straight line rather ...
-1
votes
2answers
42 views

How can we prove that electric field originate from and terminate on charge using Gauss Law?

We already know that electric field originate and terminate on charge only and they doesn't make any closed path. But is it possible to prove this statement using Gauss Law ? If yes then how ?
1
vote
3answers
44 views

Can we have electronics with charge carriers OTHER than electrons?

Ions perhaps? Or other elementary particles with charge?
0
votes
1answer
30 views

How do you calculate maximum current density for alternating currents?

I think the answer is neither here nor on Wikipedia but forgive me if it is, I don't read maths well. This question applies specifically to current density during transcranial stimulation with either ...
0
votes
2answers
42 views

How is a potential difference created between two points?

I would like to know how potential difference is created between two points?Is potential difference created by adding more electrons at one side?If that's the case how to add more electrons at one ...
0
votes
0answers
15 views

Do free charges in conductor in electrostatic field still moving even after the internal electric field is zero?

By the boundary condition, if an external electric field is apply to a conductor. The free charges of the conductor will move so that in the end There is no electric field or charge inside ...
1
vote
1answer
27 views

single conducting plane and parallel conducting plane with opposite charge all have different Electric field but same Electric Flux?

Considering the electric field $\vec{E}$ created by an infinite conducting plane $M_1$ having surface charge density $\rho_s$ locate at xy plane at $z = 0$ with $\hat{a}_z$ as unit vector ...
1
vote
1answer
22 views

where does the term half in the formula of electrostatic potential energy comes from?(system of point charges)

Electrostatic potential energy stored in a system of point charges (from wikipedia) The electrostatic potential energy $U_E$ stored in a system of N charges q1, q2, ..., qN at positions r1, r2, ...
0
votes
2answers
24 views

Ohm's law holds at constant temperature - what about Joule heating?

Ohm's law states that the resistance of a conductor is constant provided its physical conditions, such as temperature, remain constant. But what I'm thinking is that as you increase the voltage across ...
0
votes
1answer
39 views

How can equipotential planes differ in potential in an uniform field?

I'm trying to solve an exercise that asks me the field strength of an uniform electric field where equipotential planes differ by $1\ \mathrm{V}$ and are $2.5\ \mathrm{cm}$ apart. First of all, I ...
11
votes
3answers
886 views

Why do lightning rods have a sharp point at the top?

We know that a lightning rod or lightning conductor is a metal rod or metallic object mounted on top of an elevated structure and, if we look closely, most of them have a sharp point at the top. What ...
0
votes
1answer
34 views

What happens when a bird lands on a power line?

I know that when a bird is sitting on a high-voltage power line, virtually no current flows through the bird because there is (almost) no voltage drop between its legs, the two points are ...
9
votes
4answers
1k views

How electrons move so fast in a electric circuit?

Whenever we switch on a bulb......it takes almost no time to glow up.....But we know that the atoms of a solid are tightly packed and there is a very little space between them. So how the electrons ...
0
votes
2answers
29 views

Planet Sized Generator

I have an interesting idea for an energy generator and I want to see what you think. Basically, you take a small planet and drill from one side to the other so it looks like a sphere intersected ...
1
vote
1answer
52 views

Why can't I measure electric potential from source to point according to this formula

The formula for electric potential of points A and B in the presence of an electric field due to a point charge where $R_a$ and $R_b$ are the distances from source to point A and B respectively is: ...
0
votes
2answers
23 views

Calculating the energy supplied by a battery

If you wanted to calculate the energy supplied by a battery in time $t$ you would use $E=VIt$ where $I$ is the current through the battery. If the internal resistance is $r$ we could also use ...
1
vote
1answer
34 views

Ampere's Law and Gauss's Law for EXACT CENTER of Finite Wire: Mathematical Justification [closed]

I have always seen it explained that: Ampere's Law (in integral form) works whenever B is constant around a path, so that you can pull it out of the integral. Similarly, if you can draw a ...
1
vote
1answer
26 views

Static electricity and insulators

I've read that Stephen Gray in his experiments on electricity, he has found that static electricity can be conducted -transferred- through an insulator thread made of silk. So, how could that happen ...
1
vote
1answer
28 views

Question about ohmic conductors

I'm having some trouble understanding Ohm's law. My trouble is with the different ways it is described when referring to ohmic and non-ohmic conductors. If someone can answer this question I think it ...
1
vote
2answers
48 views

Resistors in parallel: How do I make this rigorous? [closed]

In my revision guide it says "when two resistors are in parallel, the current has two paths it can flow through so there is less opposition to the current. This is why the combined resistance is less ...
2
votes
2answers
37 views

How is resistance defined when there is no current?

By definition, a component has a resistance of $1\Omega$ if a potential difference of $1$V makes a current of $1$A flow through it. So I was a bit confused when I saw somewhere "a filament lamp has a ...
2
votes
1answer
13 views

Need help understanding appliance ratings

I keep coming across things like "A filament lamp rated 12 V, 1.0 A", or "a heating element rated 230V, 500W". I think the first one is saying that a 12V potential difference across it will make a ...
0
votes
1answer
24 views

Experiment for finding resistivity

I was reading an experiment to measure the resistivity of a wire. I understand everything except for why the variable resistor is connected to the side of the positive terminal of the battery. Since ...
0
votes
1answer
17 views

Potential difference of conductor with induced load

If a metallic sphere is grounded and close to a positive charge q, it will be charged with -q. Let's say that the electrons will arrive through the grounding. This charge will cover the surface of the ...
0
votes
0answers
10 views

Circuit providing output? [migrated]

What does it mean for a circuit to provide an output power of say 1000W? Is "circuit providing power" referring to the battery supplying energy to the external circuit, or is it referring to the power ...
0
votes
1answer
31 views

Difficulty understanding electricity concepts

In circuit diagrams what does it mean for energy to be used in going through a component? I usually see this when emf is being described: total energy supplied per coulomb by battery = total energy ...
0
votes
1answer
15 views

Inductor in transformer

In an inductor, a current waveform 90 degrees out of phase with the voltage waveform creates a condition where power is alternately absorbed and returned to the circuit by the inductor. If the ...
-1
votes
5answers
49 views

Convert kinetic energy of a bullet into electricity and store it in a super-capacitor [closed]

I was thinking about bulletproof materials, they have to be so thick and heavy because they try to hold all of the kinetic energy of a bullet and then dissipate it (right?) So what if you made a thin ...
1
vote
1answer
37 views

The Faraday experiment about electric displacement field

I read the description and the explanation of the result of the experiment in my book but still I can't understand it. Here is the process of the experiment. A pair of concentric metallic spheres ...
1
vote
1answer
23 views

How is the efficiency of an electric motor affected? [closed]

Consider that I'm having a motor (AC/DC) and the power switch is on and it's being supplied power and of course the motor is rotating. Now, I continuously start switching off and on the power. For 1 ...
4
votes
1answer
36 views

Why an inductor parallel with a light bulb makes it flash as a key closes the circuit?

The title is a simplified form of my question. To be precise, I'm talking about the following circuit: The inductor has a resistanse equal to the resistor in the circuit. So, the question is that, ...
3
votes
1answer
96 views

does a resistor slow down the flow of electrons or just let less electrons through? or is it both?

I like to have an intuitive grasp of whats happening our tutor said they 'resist' the flow of electrons but I want to understand exactly whats happening.