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

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268 views

Voltage and current in parallel circuit

I am having a bit of a tough time understanding the following: ...
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685 views

How can one explain the Kelvin Water drop experiment without assuming the container to already possess a positive charge?

Kelvin Water Dropper experiment refers to the electrostatic generator invented by Lord Kelvin, which uses falling water to generate a voltage by electrostatic induction occurring between ...
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1answer
1k views

Power loss and Joule's law of heating

I really can't understand the power loss law. If we have a wire carrying a $15\:\mathrm{V}$ and $1\:\mathrm{ A}$ going into an inverter, giving $150\:\mathrm{V}$ and $0.1\:\mathrm{A}$, if we want to ...
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0answers
282 views

What's the typical material used as a low-k ILD in semiconductors?

Semiconductor companies (namely IBM, Intel, TSMC and etc.) may use different low-k materials as inter-layer dielectric (ILD) in their fabrication process. I'm wondering what is the most typical one. ...
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1answer
790 views

Use kirchhoff's second law to deduce the resistance R of the resistor [closed]

Using what I learned so far, i constructed an equation like this: $$30V=(I_{1}\times 20\Omega)+10V+(0.2A\times 10\Omega)+(I _{3}\times 10\Omega)+(0.5A\times R)$$ Which is clearly not solvable on its ...
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2answers
7k views

How do stun guns not kill people?

Now, I've seen a lot of answers to this sort of question, but most of them provide answers that don't actually make sense from a physics perspective. As an example of such an answer, I've commonly ...
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1answer
132 views

E&M question in example in my book [closed]

So I still not sure how to apply like Right-hand rule (RHR) in this setup in problem like the one in the following so I tried to do RHR in order to get the direction but it didn't work out. This is an ...
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2answers
435 views

Do glass beads show any piezoelectric property?

Do glass beads show any piezoelectric property? Since glass beads is mostly made out of SiO2 which is piezoelectric, will it show any piezoelectric property. Thanks. If anything wrong with my ...
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3answers
1k views

Current without voltage?

Suppose you have a 120 volt, 20 amp circuit which only has a light bulb connected. When measuring the voltage going to the light bulb my meter reads 120 volts. The basics taught me that a circuit is ...
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1answer
278 views

Where does energy in electricity come from?

In a simple battery-wire-lightbulb circuit the moving electrons in a wire generate electromagnetic field, and that field transports energy. And the bulb goes light. But where does the energy come ...
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3answers
3k views

Electric heating rod

I usually heat my bathing water with electric heating rod, I always thought that the base of rod is an insulator so that it can develop high heat. But when I tried touching water while rod was dipped ...
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1answer
6k views

How to evaluate, how much current flows in the circuit?

Please take into advisement, that I'm quite a beginner in subjects of physics and especially about electricity. Lately I've decided, that I want to learn more on basics of electronics and I've started ...
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3answers
273 views

Why are high voltage lines “high voltage?”

If I have two spheres of the same size and one sphere has a small amount of charge compared to the other that has a lot more charge, then clearly the sphere with the larger charge has a larger voltage ...
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1answer
245 views

Magnetic core, and a DC solenoid

A DC solenoid creates a magnetic field B. A highly permeability magnetic core is added to solenoid to increase B. Now, there is change in flux, due to the increase in magnetic field. What would be ...
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4answers
2k views

How can there be a current and an electric field in an idealized wire with no voltage drop?

In an ideal circuit, How can there be a current b/w points a & b, when there is no potential difference and thus no electric field between a & b? If there is no current, then where does ...
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2answers
215 views

How long does it take for a metal to reach equilibrium?

I wonder if there is a measure of how long a piece of metal takes to reach electrostatic equilibrium. Does it depend on piece's size? Does it depend on the amount of imbalance? Lots of websites and ...
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1answer
160 views

Tungsten Wire Heat discipation

Background Information: I'm doing an experiment in which I place a bare tungsten wire in to various liqids, to measure a coefficient $\alpha $ in the equation $$ Power Dissipated = \alpha * \Delta T $...
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2answers
92 views

Calculating the power of a lightbulb [closed]

How do I calculate the power of a lightbulb? I have values but I don't know the equation to use.
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1answer
134 views

Calculate required voltage in mixed circuits [closed]

Q: Calculate the voltage that V1 has to provide Given: The following circuit. The voltage through LAMP1 is 5.0V. A (U,I) chart (not shown). LAMP1 and LAMP2 are identical, non-ohmic lightbulbs. ...
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2answers
210 views

What is the Definition of Static Electricity?

What is the Definition of Static Electricity? My grade nine textbook states: Static electricity is the imbalance of positive and negative charges. What exactly does this mean? I understand ...
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1answer
90 views

Power and magnetism

If we have a solenoid and a magnetic field passes through it, a DC voltage will be produced in the wire. If we want to calculate the power, we find out the current using Ohm's law. I know there is ...
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1answer
913 views

Why is it written 'High voltage' in danger boards if current is the one which actually causes the shock?

After reading the answers given to this question I could understand that the amount of shock is dependent on the current and not majorly on the voltage even-though in some cases it depends. But, in ...
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1answer
157 views

What makes charges flowing in a circuit with a higher potential difference perform more work?

I understand that a 1.5 V cell will not deliver as much energy per coulomb as a 150 V power supply will. What I do not understand is that why it is so. I am digressing now. If we place two point ...
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1answer
357 views

Electric field and capacitance across a resistor

Using a simple lattice model of conduction, where electrons are accelerated by an electric field, and are slowed down by bumping into the lattice, you get the following equation for current density: $...
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1answer
2k views

Electric Field from Dielectric Shell

This is a question taken from a past E&M exam A thick spherical shell (inner radius $R_1$ and outer radius $R_2$) is made of a dielectric material with a "frozen in" polarization $$P(r)=\frac{...
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1answer
1k views

How does a Tesla Coil exactly work? [closed]

How does a Tesla Coil exactly work? I am currently making a Tesla Coil in school but before I start, I want to know exactly how does a Tesla Coil work? I understand the various electrical components ...
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2answers
78 views

Direct current and metallic conduction

Suppose we have a circuit with and EMF source and a resistor. We know that when electron moves from one terminal of a voltage source to another it encounters resistance, which is basically collisions ...
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2answers
6k views

How does an electric field come inside a conducting wire inside the circuit? [duplicate]

This has been a really great confusion for me now .... Many places I have read in books that when a potential difference is applied across the ends of a wire a constant electric field is generated ...
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1answer
129 views

Electrical circuits problem

Batteries have a circuit which looks like this : The electrons go around the circuit and then return through the battery where they get charged again and flow around. My issue is, what about ...
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1answer
322 views

Find current in a nontrivial circuit

Let us assume that we have this circuit: We know that: $$I_1 = I_2 + I_3$$ $$I_1R_1 + I_3R_3 = V$$ $$I_1R_1 + I_2R_2 + \dfrac{q_c}{C_1} = V$$ Therefore we can write: $$I_1 = k_1 - k_2*q_c$$ ...
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6answers
23k views

What are the fields produced around a current carrying conductor?

If you consider a current carrying conductor, every instant an electron enters the conductor, another electron will be leaving the conductor. Thus, the current carrying conductor will not be charged (...
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3answers
209 views

Will the current carrying solid conductors emit light?

If we pass current through a gas, like in the discharge tube, the electrons will accelerate in the electric field. The accelerated electrons will collide with gas molecules, and transfer some of their ...
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1answer
272 views

traditional transformer design improvement [closed]

The traditional tranformers suffer a lot of losses in various forms, some of them are as follows : 1. Flux leakage 2. Eddy currents 3. Hysteresis Figure : But as we are taught induction we come ...
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0answers
121 views

Benefits of the sign convention for electrons?

Benjamin Franklin considered electrons to be positive, but J.J. Thompson considered them negative. We obviously went with J.J. Thompson's convention. Why? What were the benefits of moving to J.J. ...
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179 views

How is derived the relation between capacitances when a $Y-\Delta$ transformation is applied in a capacitors network?

A $Y-\Delta$ transformation can be applied to circuits in order to make an equivalent circuit (but simpler to put in terms of series/parallel devices). Wikipedia and other books show how to deduce the ...
19
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3answers
687 views

Why can't batteries be charged quickly?

Charging of laptops, cell phones take so much time. Why can't we make such batteries easily/commercially which are charged more quickly? What's the thing behind this limiting?
2
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1answer
78 views

Plasmon Based Transistor vs conventional one

Conventional wires become very lossy at high frequencies. Is this because of the skin effect? Plasmon based computer chips, since plasmons can support much higher frequencies (~100 THz range). ...
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3answers
17k views

Why current through all the resistors in series is considered to be same? [duplicate]

Consider the circuit shown, where $R_{1} > R_{2}$. I meant to say that resistance offered by the resistor 1 is greater than the resistance offered by the resistor 2. Keep $t$ constant i,e calculate ...
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1answer
114 views

Resistances in a circular loop

I have no idea what formula I'm supposed to use.I just want to know the concept that would allow me to get the answer. I know basic concepts of electricity like charge, currents, etc., but as far ...
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1answer
3k views

Why the electric bulb turns on almost instantly when the switch is closed? [duplicate]

The electron drift speed is estimated to be very low.How could there is current almost the instant a circuit is closed?? By the discussions it is known that The information about beginning of the ...
5
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3answers
4k views

Do electric and magnetic lines of force physically exist?

As per my imagination any thing can't impose force on the other by not giving even a touch(i,e action at a distance). So I thought there must be some physical existence of lines of force. Although ...
4
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1answer
511 views

Question about superconductivity

A long cylinder of radius $R$ is made from two different material. Its radius $r<r_0$ $(r_0<R)$ part is a material with superconducting transition temperature $T_1$, and its $r_0<r<R$ ...
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2answers
81 views

What is the distinction between thermal and electrical conductivities?

Aren't they both caused by electron motion?
3
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1answer
3k views

How does a crow sitting on one of the electric lines attain the same potential as that of the line so as to prevent a charge flow through its body? [duplicate]

The crow doesn't get an electric shock while sitting on only one electric line because it has the same potential as that of the line. Since there is no potential difference the charge does not flow ...
2
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0answers
390 views

Calculating Electric Field from a Potential Difference w/o Charge

So here is my homework question: Two long cylindrical shells of metal (radii $r_1$ and $r_2$, $r_2 > r_1$) are arranged coaxially. The plates are maintained at the potential difference $\Delta\...
2
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2answers
239 views

Strange electrical circuit

This is a question I would like to have an explanation with: It's in this PDF, question 9. In that circuit, if switch 1 is closed, bulb A burns normally. If 2 is closed as well, do other lamps ...
4
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2answers
725 views

Will there be any force of attraction or repulsion between an electrified body and a non-electrified body?

Up to my knowledge an electrified (charged) body can attract a non-electrified (neutral) body. I thought this because, when we bring a charged (suppose negatively charged) body near a neutral one. ...
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1answer
501 views

How does current work

In all diagrams i have ever seen of circuits it's implied that electrons travel through load/bulb and bulb makes light/heat. Now there is a problem here...because of this implied logic i assumed more ...
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2answers
138 views

Does a battery in a vacuum produce a current?

I've always assumed that the strong resistance of air is the reason there is no flow of electrons between the terminals of a battery until a wire is connect. However, in a vacuum there is no resistive ...
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2answers
3k views

Why is the voltage drop across an ideal wire zero?

I'm having trouble conceptualizing why the voltage drop between two points of an ideal wire (i.e. no resistance) is $0~V$. Using Ohm's Law, the equation is such: $$ V = IR \\ V = I(0~\Omega) \\ V = 0$...