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

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How magnets create electricity in conductors?

what are the reasons for current appearing in a wire when wire is in a changing magnetic field?
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262 views

Radiation at plate of vacuum tube

Say you have a vacuum tube, such as the kind used in old amplifiers, wherein electrons are accelerated from the cathode to the anode through an electric field. Presuming, for the sake of argument, ...
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69 views

Objects made up of electrons?

Say you have a neutral rod, and you bring a positively charged rod beside it (call the side the charged rod is brought near side A and the other side side B). The electrons from the side B will start ...
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58 views

Electromagnetism Permittivity simple question

Just a simple question regarding $\epsilon$, the absolute permittivity. I read that it measures the resistance to of certain medium to 'permit' the formation of an electrical field. Does this mean ...
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158 views

Batteries connected in Parallel

"If we connect two batteries in parallel, the battery with higher voltage will discharge into the other one." What is the intuition behind this?
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52 views

Electrode potential

If I connect a zinc half cell (Left hand side) and a copper half cell (right hand side), I get an E cell value of 1.1V taken from the voltmeter. If I replace the voltmeter with a light bulb, I will ...
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2k views

What happens when a charged (negative or positive) object touches an insulator?

I know that insulators do not conduct electricity because they do not allow the free movement of electrons. Let's assume the object that's going to touch the insulator is negatively charged. Does some ...
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52 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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55 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 ...
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93 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 ...
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123 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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87 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 ...
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101 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 ...
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224 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
503 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 ...
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1answer
116 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
251 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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90 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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1answer
940 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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5answers
21k views

Why does voltage remains same over Parallel Circuit

Why does voltage remains same over parallel circuit. If a resistor is connected in the circuit some of the charge should be transformed into heat and make a lack of charge after the resistor (in my ...
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331 views

Effective Resistance [closed]

For the combination of the resistors, shown in the figure. Calculate the equivalent resistance between A and B, please help me to find the answer of this complicated question this is a question from ...
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1answer
896 views

Voltage and parallel-plate capacitors

Suppose we have two parallel plates (each of area $A$) spaced with distance $d_1$ acting as a parallel-plate capacitor within a circuit. If the capacitor is connected to a power source with constant ...
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1answer
513 views

Self-sustained vs. non-self-sustained discharge systems

I don't quite understand what a self-sustained discharge is. I figure it means that the processes involved are self supporting and generate themselves, so that I don't have to put energy into the ...
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1answer
479 views

Conductor resistance calculation method

1. What are the variables that effect on a conductor resistance (I mean all of them)? First of all I would like to say that I know how to calculate the resistance of a conductor using the method ...
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2answers
434 views

Drawing electric field lines-Equations or software

Shown below in the diagram are two conducting material connected to a battery source and vacuum OR air is in between them. There will be charges developed on their surfaces. I am interested in finding ...
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1answer
97 views

What type of magnetic fields does a Hall effect semi-conductor pick up on?

What type of magnetic fields does a Hall effect semi-conductor pick up on? AC or DC fields? How would one go about building a device that measures AC Magnetic fields?
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168 views

Are two touching conductors connected in parallel or in series?

Consider the following problem: There are two spherical conductors $A, B$, with capacitances $C_A, C_B$ resp. Conductor $A$ is supplied some charge and is found to have a potential of $160 \space V$. ...
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277 views

scaling of motor power

For car engines, the cylinder volume is often associated with the engine power, which suggests scaling of the power as $L^3$ where L is the linear size. Consider a system consisting of a motor and its ...
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111 views

Need an intermediate resistivity part/material

I need a part or material for a planned experiment (the experiment is similar to those described in my articles http://arxiv.org/abs/1208.0066 and http://arxiv.org/abs/1109.1626 ). The problem is that ...
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1answer
1k views

Charging by induction (and grounding)?

The very familiar phenomenon of charging by induction includes bringing a charged object near an uncharged sphere to induce a separation of charges in it and then grounding the charge (same as the ...
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1answer
68 views

Electricity directly from heating a material [duplicate]

I am looking for some more information about how to obtain electricity from heat directly. This e.g. involves the Seebeck effect, as I have found it is called, where a material produces a voltage ...
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1answer
54 views

Total current of two sources in series? [closed]

Here is a question that a friend asked me. He had to an experiment in school and do some calculations afterwards. Those calculations require maximal current that the DC source can produce. He has ...
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1answer
82 views

Lightning and Charge Displacement

There is something I don't really understand about flashes of lightning. When a flash occurs, how come electricity be transferred at the speed of light since electricity's displacement is very slow ? ...
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1answer
7k views

Volts, Amps, and Practical Electrical Knowledge [duplicate]

I've heard people say that high amperage or high voltage is dangerous to humans-aren't they both? And what are the advantages to high amperage versus high voltage? And how do you generate one or the ...
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1k views

Charging Glass Rods

When we rub two glass rods with their respective pieces of silk cloth, the two glass rods would repel each other. What if we rub the glass rod against the other glass rod? Will they repel each other? ...
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90 views

Is there a material that changes local conductivity

I hope this is the right forum to ask this question. Is there a material (preferably thin, like a membrane) that changes its local conductivity (by that I mean the permeability for an electric field; ...
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487 views

Why the CFL light bulb flashes even if there is a power cut?

Today when there was a power cut I saw that the CFL light bulbs were flashing time to time at regular interval. I was amazed as there was no source of power to the CFL bulbs even they were flashing as ...
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1k views

Finding Current and Voltage through resistors given overall voltage and resistor values

Given a setup like: Is it possible to find current and voltage through each resistors given resistor values and overall voltage (battery voltage I suppose). I think $$I_0=I_A=\frac{\Delta ...
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773 views

Finding and plotting the current graph from a voltage graph (piecewise function)

Problem description: My attempt at making the piecewise function: Then, in order to find i(t), I took the derivative of 80x/3 and -80x/3, with respect to x, and multiplied C. Obviously, I'm left ...
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1answer
1k views

What does a positive gradient on a graph of V plotted against I mean in terms of EMF and internal resistance?

According to the equation $V = E-Ir$, the gradient of a graph of $V$ against $I$ should be $-r$ (internal resistance) and the Y intercept should be the EMF. Am I right? In an experiment I used a ...
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744 views

Capacitance and Light Bulb And Dielectric Slab [closed]

An electric lamp having coil of negligible inductance connected in series with a capacitor and an AC source is glowing with certain brightness. How does the brightness of the lamp change on reducing ...
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1answer
152 views

Battery fully loaded, pull out the chord?

I recently bought a new phone (Samsung Galaxy 3) and when the battery is fully loaded, it says like "Battery fully loaded, pull out the chord". Is this a typo from Samsung, or would there ...
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2answers
199 views

pattern of moving electrons in wire under AC

when we use a DC battery into a circuit the flow of electrons in wire creates a clear picture as they flow from negative terminal to positive terminal. under AC(Alternating current) we know how energy ...
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1answer
706 views

Light bulbs with voltage source or current source

When we connect 2 light bulbs to a voltage source in parallel, the equivalent Resistance of the bulbs is R/2 (1/Req = 1/R + 1/R). If we connect these lights in parallel we have Req = 2R; I= V/Req is ...
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197 views

Does using batteries in a series raise the overall Wh's of the batteries used? Why/Why Not?

If one has 2 batteries of 6 Volts each with 500 mAh each, then separately the batteries should provide 6 Volts * 500 mAh = 3 Wh each or 6 Wh total. However would it be the case that if someone where ...
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1answer
357 views

Question Based On Direct And Alternating Current

A Wikipedia article on Power engineering reads, Most refrigerators, air conditioners, pumps and industrial machinery use AC power whereas most computers and digital equipment use DC power. As ...
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1answer
272 views

Tubelights+power lines pictures?

I've come across many pictures like these, sometimes in chain emails reporting the dangers of power lines. Another claim is that they run on "wasted" energy. The explanations given are that the ...
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1answer
257 views

Magnetic Susceptibility- Permeability

What is the permeability of magnesium sulphate and therefore the magnetic susceptibility?
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331 views

polyphase circuits

I was going through a physics book which contains a short description of Nikola Tesla . The description mentioned about poly phase circuits (power supply). Out of curiosity I googled it up and I found ...
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4k views

Internal resistance V=IR circuit question [closed]

I don't know how to resolve this problem. A complete circuit consists of a 18,0 V battery (internal resistance r) and a resistor R. The terminal voltage of the circuit is 15,8 V and the current is ...