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

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2answers
446 views

Is the Earth negatively or positively charged?

The Earth carries a negative electric charge of roughly 500 thousand Coulombs. Does that mean the Earth is negatively charged?
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2answers
161 views

Is a billion volt electrical transmission line possible?

Because $$ P_{loss}=\frac{P^2R}{V^2} $$ in an electrical line where R is total resistance Why not use a 1 billion volt line instead of a 800kv line? Is there a maximum voltage that copper can carry? ...
0
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2answers
202 views

How exactly does WiTricity's wireless power transfer using resonance work?

The WiTricity group has made a lot of buzz but no internet article explains the exact method that they are using. Does any one know how it works?
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1answer
49 views

Applying more current? [closed]

An electric motor draws 20 Amps, when at maximum load of x. Can that value of current be applied even if the load was ten times less than x from a certain power source?
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1answer
46 views

Calculating Energy & Small functional time scale

I have an electric motor that can apply a pull force of $3000 \;\mathrm{lb}$ (electric winch), it draws $180 \;\mathrm{A}$ at $12 \;\mathrm{V}$. I understand that power $P = I \cdot V = 2.1 ...
0
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1answer
86 views

Is there another way besides $V = k\int dq/r$ to find potential?

Suppose that the charge distribution $q(r)$ in the radial $r$-direction in a thin hollow disc of inner radius $a$ and outer radius $b$ is given by the power-law equation: $$q(r) = Q_0 \left[1 ...
1
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2answers
231 views

What do we mean exactly by the positive/negative charges in cathode and anode?

In batteries, what exactly do we mean by negative and positive charges? My understanding is that the negative charge of the anode is basically an atom with an extra electron in the last orbital and a ...
0
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1answer
110 views

Can capillary forces be used to make hydro electricity?

Could a device with very thin columns of glass or something that attracts water more be used to pull water up and then release it to drive generator and perhaps add vacuum. I have been wondering ...
0
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2answers
155 views

How do voltage and voltage drops over a circuit relate to work done?

I have a few remaining uncertainties when it comes to voltage. I numbered the paragraphs in my thought sequence for easier reference. In a series circuit, I know voltage is the electric potential, ...
1
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1answer
78 views

Converting heat into energy [closed]

I'm currently building a custom desk. In this desk I will also build-in a small part with a custom electronic panel to provide power to USB devices. As my gaming pc generates a lot of heat and the ...
1
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2answers
321 views

Questions about voltage

For some reason, I feel like the concept of voltage is escaping my grasp. I've done much research on these forums and through texts, and come across answers that seem quite well thought out, but still ...
0
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2answers
81 views

Complex impedance triangle, why is there a complex part?

Why is the inductive reactance written as jωL? I know that multiplying by j rotates the inductive reactance on the j axis, but why do we do that? Why is it not on the same axis as the resistance?
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2answers
78 views

Transmit DC power with one cord?

My DC devices have two wires connecting them to the power source, but what would be needed to transfer DC power using just one? I depict it as a kind of headphone, which can work with just one wire.
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2answers
72 views

How does one estimate the electrical power of a power plant?

I have two related questions that I would like help on: When a power plant creates power like the Hoover Dam, it can provide 2.07 GW of electrical power. My question is what does this mean? I assume ...
0
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3answers
64 views

Capacitor related query

Why does a capacitor charge only upto the voltage of the source? I mean in an r.c. circuit if we have a resistor that is in series with the capacitor then because of the potential drop there will be ...
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0answers
31 views

Formation of magnetic field in an inductor

I can't really imagine the way the magnetic field would be created due to electron flow in an inductor. We say that in a straight current carrying conductor the magnetic field follows the thumb rule. ...
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3answers
86 views

Relation between voltage and current [duplicate]

What I know is that voltage is the electrical pressure which is required to drive the electrons in a circuit. According to that we have higher currents when there is a high voltage. Ohm's law confirms ...
0
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5answers
376 views

How would I explain Ohm's Law in terms of Electrical Fields and Force?

In terms of current, resistance, and voltage, it's easy: Ohm's Law is the relationship between current, voltage, and resistance of a circuit. Boom, simple as that. How could I put this in terms of $E$ ...
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1answer
177 views

how can electromagnetic waves reach a cell phone in faraday cage?

is there any way to make electromagnetic waves reach a cell phone in faraday cage although conductor surround cell phone everywhere , can we pass current through conductor to make charges move as a ...
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2answers
46 views

Yearly onshore wind turbine energy production [closed]

I am trying to work out the yearly energy production of an onshore Siemens SWT-3.0-101, hub height 94m, total height 144,5. Here is the power curve at each wind speed level worked out through a ...
0
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1answer
90 views

Do electric fields generated by plane charges lose intensity over distance? If not, why?

Sparknotes' studyguide for the SAT II: Physics test says that for a point charge (1-dimensional, e.g. an electron), the formula for intensity of the generated electric field is given by ...
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1answer
96 views

Can wire not melt under the current of a lightning?

In a recent Hunger Games movie, there's a scene where a certain scientist says that he invented a wire which will not melt under the current of a lightning. Is that even possible?
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1answer
89 views

Voltage and current in parallel circuit

I am having a bit of a tough time understanding the following: ...
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1answer
96 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
140 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
38 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. ...
0
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1answer
176 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 ...
4
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2answers
490 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 ...
0
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1answer
102 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
70 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 ...
0
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3answers
143 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 ...
0
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1answer
80 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 ...
0
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3answers
412 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 ...
0
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1answer
438 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 ...
2
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3answers
132 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 ...
0
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1answer
53 views

Load on a generator

I am really stuck on this and I couldn't find any references on the internet regarding this. When a load is connected to a generator, why does the current drawn from the generator increase. Since the ...
0
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1answer
116 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 ...
3
votes
4answers
347 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
92 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 ...
0
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1answer
46 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
57 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.
2
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1answer
82 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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0answers
403 views

Finding potential difference (PD) between two points [closed]

How do I find the potential difference between two points in a circuit without using Kirchhoff laws?
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2answers
91 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 ...
1
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0answers
37 views

Lorentzforce and righthand rule [closed]

Figure 1: A spool is hung on a spring. A part of the coil hangs in front of a homogeneous magnetic field. The coil is incorporated in an electrical circuit. See Figure 1. the coil ...
1
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1answer
55 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
166 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 ...
1
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1answer
70 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 ...
1
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1answer
103 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: ...
3
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1answer
516 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 ...