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

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2answers
380 views

Potential difference with an inductor

As far as I know, the potential difference between two points is defined as the negative line integral of electric field between those 2 points: $$\Delta V=-\int d \ell\cdot\mathbf E$$ I also know ...
2
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2answers
348 views

Why do electrons drift in an ideal conductor, since there's no field?

Suppose a simple circuit with a DC voltage source and a resistor. The voltage of the source will be situated over the resistor. So the electric field (which is the gradient of the potential) will be ...
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0answers
11k views

Why do current and electrons flow in opposite directions? [duplicate]

In representing an electric circuit, we would draw the sense of the current from the positive to the negative pole and the electrons from the negative to the positive . But as I know electrons' motion ...
2
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0answers
50 views

Is it possible to generate usable electricity from the motion or magnetic field of the Earth? [duplicate]

Let me start by saying that my knowledge of physics is almost nil (only high school level and I pretty much forgot everything) so bear with me, if I am asking naive questions the answers of which may ...
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2answers
272 views

Battery and current confusion?

How exactly does a battery produce a current in the circuit connected across its ends? I dont want to know the chemical reactions in the battery core, but just the essence of it. I believe it doesn't ...
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2answers
104 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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0answers
40 views

Experimental study of the Photoelectric effect [duplicate]

As I was reading about the experimental arrangement for photoelectric effect, I saw a diagram that puzzled my knowledge of electrodes. I found that in the experimental setup the cathode of the ...
0
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1answer
67 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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6answers
7k views

Is it possible to generate electricity using a water tower?

Is it possible to build a water tower that will provide enough pressure to run an electricity generator? A water pump can be used to send water up to the tower. The water pump can be powered by solar ...
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1answer
202 views

heat energy and resistance of an elctric circuit

Very often it is said that "heat is developed" in a resistance when there is an electric current in it. But as far as I know heat is defined as a form of energy being transferred due to difference in ...
5
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2answers
8k views

Why do two connected 1.5-volt batteries become a 3- volt battery?

Why two connected 1.5 volt battery become 3 volts? If one battery plus side is connect to minus side of another battery, there should be a current flow between them until no free charge move anymore, ...
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0answers
102 views

How to size an electromagnet

How can I size an electromagnet? For example if I would to attract a mass of $x$ kg what are the calculations that I must do to size the ferromagnetic core and of course the solenoid? And thus, how ...
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1answer
1k views

Why does a moving electric charge have nonuniform electric field lines?

The electric field of a stationary electron is uniform, radially symmetric with straight field lines. However, the electric field of a moving electron still has radial and straight field lines, but ...
5
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2answers
194 views

How does current flow in a irregularly shaped heterogeneous resistor?

The motivation for my question is understanding how electricity gets through your skin as opposed to running along it, and how the presence of things like water on the skin affect the relative ...
11
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5answers
876 views

Why are wires in simple circuits approximated as equipotentials?

I just answered this question: Voltage in a circuit by asserting that any two points joined only by a wire, but no other circuit elements, are at the same value of the electric potential. It is, of ...
4
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2answers
220 views

Voltage in a circuit

Suppose I have a following circuit: I do not understand, why the potential difference between the points $c$ and $d$ is equal to the potential difference between the points $b$ and $a$? That is, ...
0
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0answers
94 views

Electrical properties of molten gallium arsenide

I'm looking for the resistivity and magnetic permeability of molten gallium arsenide, but can only seem to find the values for the solid material at room temperature (e.g., Wikpedia). Not even ...
12
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4answers
1k views

What could magnetic monopoles do that electrically charged particles can't?

I understand the significance to physics, but what can a magnetic monopole be used for assuming we could free them from spin ice and put them to work? What would be a magnetic version of electricity? ...
2
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1answer
2k views

How are excess charges distributed over non-spherical conductors?

My textbook gives the following explanation on how excess charges are spread over conductors: The excess charge on an isolated conductor moves entirely to the conductor's surface. However, ...
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1answer
72 views

Would the empirical behavior of a simple circuit match my model of it?

I have a practical problem in E&M which has baffled me and and my electrician. The copper water pipes in my house are carrying a current of small potential (~1V) AC current. Here is my ...
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0answers
123 views

About electric current analogy

my teacher gave me this analogy to the electric current , the wire is like a pearl necklace where the pearls can move, the current or the movement of electrons is like putting your fingers between 2 ...
0
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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 ...
5
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1answer
2k views

Does rubber insulate lightning more effectively than air?

Last week, an Ars Technica writer was struck by lightning. He says that the 911 operators were concerned about whether or not he was wearing shoes at the time, but he didn't think it would make much ...
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1answer
264 views

Power in hydraulic analogy

In hydraulic analogy one compares electrical circuits with water circuits. For the electric case the formula $P = U \cdot I$ for the electric power holds. The analogous formula for water flow would ...
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2answers
195 views

Street Light Interference Phenomenon [closed]

Is there a scientific approach that can explain the street light interference phenomenon? Everytime I walk past a Streetlight it turns off.
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0answers
24 views

Faraday Effect, Satellites, and Electromagnetic Atmosphere [duplicate]

If I launched a Satellite into orbit and dropped a silver wire caged in carbon fiber with aerodynamic wings (for support), would the Faraday effect of the wire traveling through earth's ...
0
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1answer
80 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 ? ...
0
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1answer
114 views

Current in AC circuit

The problem is to find the current on the capacitor. $I''$ should be correct, but I don't know how to construct the formula for $I'$. I managed to get the value for $I_c$ using Thevenin and Norton ...
0
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2answers
11k views

What happens when non-equal voltages are put in parallel? [duplicate]

If two batteries, say 2 volts and 5 volts, are connected in parallel, are there any problems? The higher voltage will then want to flow out, but also towards the lower 2 volt battery end, right?
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1answer
555 views

Why should a battery not give current in order to measure EMF?

Emf is the "potential difference (PD) across the terminals of a battery when it is giving no current to the circuit." What does "when it is giving no current mean"? Will the PD across the terminals ...
2
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1answer
128 views

Help Understanding Non-conservative Fields

While watching a video lecture, I became uncomfortable with the results, (around 35 mins). The professor draws an electric circuit with a 1V batter, and two resistors (1 and 9 ohms). He then ...
5
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3answers
11k views

Can the Earth's magnetic be used to generate electricity?

Since the Earth has a magnetic field, can it, in theory, be run through a conductive metal coil to create electricity?
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1answer
113 views

The nature of resistance at copper wire terminations

Speaker wire consists of twisted copper strands, around AWG 22 thru 10. As good consumers know, one must consider resistance when wiring speakers. How do the wire terminations contribute to the ...
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1answer
69 views

Contact electricity and photoelectric effect

Most universities provide an experiment about the photoelectric effect to determine $h$ by measuring the stop voltage against the light frequency and calculating the slope $h/e$. But mostly they also ...
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4answers
248 views

What is a “gravitational cell”?

I am not a physicist, and I don't understand the details of electromagnetism. Anyhow, I was looking for how the batteries work in Google. So, I came across this article: "How batteries work: A ...
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1answer
6k 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 ...
0
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5answers
129 views

The potentiality of the electric field

Could you please explain using just words why electric the field is potentially? I know the proof using integral: $$A = \int_{12}q\vec{E}\cdot{d}\vec{r} = qQ\int_{12}\frac{\vec{r}\cdot{d}\vec{r}}{r^3} ...
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2answers
3k views

Voltmeter forming a closed circuit

A battery is connected to a 10Ω resistor as shown in Figure 2. The emf (electromotive force) of the battery is 6.0 V. When the switch is open the voltmeter reads 6.0 V and when it is closed it ...
5
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1answer
3k views

How Special Relativity causes magnetism

So my physics teacher assigned us an article about how special relativity causes magnetism in a wire with a current, even with the low drift velocities of electrons in a current. It seemed that the ...
6
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3answers
14k views

Why does increasing the temperature of a thermistor decrease it's resistance?

Surely, upon an increase in temperature, the atoms within the thermistor would vibrate with more energy and therefore more vigorously, hence making the electrons flowing through the electric circuit ...
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1answer
1k views

Speakers and Static from Hands

Why is it that when you touch the a bare male end of a speaker feed that the speaker makes hissing noises? Is it just (eddy?) currents running through you?
4
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3answers
20k views

Different batteries connected in parallel

If we have 2 batteries one of emf x and the other is of emf y and we connect them in series we get an effective emf of x+y. But what if we connect them in parallel, how to calculate the emf now?
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2answers
549 views

Do black holes have charges?

Do black holes have charges? If so, how would they be measured? Also, does electricity behave the same way? Black holes affect photons, which are carriers of EM radiation, so do black holes have any ...
1
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2answers
328 views

Simple ohms law on a battery ? Paradox or conceptual error?

Suppose we have a regular pencil battery which supplies DC voltage $V$. Say we take copper wire and connect the ends of the battery to an $R$ ohms resistance. Then Ohm's law tells use the current in ...
4
votes
2answers
15k views

Why don't electric workers get electrocuted when only touching one wire? [duplicate]

I know that when electricians work on the poles on the streets, if they only touch one wire at a time they will be fine. However, from my understanding, the negative wire is connected to a large ...
4
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5answers
12k views

Why does the comb attract the pieces of papers if they're neutral?

When we rub our hairs with a comb, and then try to attract small pieces of paper, they're attracted by the comb. The pieces of the paper were not electrified before they were attracted. Then they ...
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0answers
64 views

Early Concepts in Relation with the Forces Produced When Certain Pairs of Objects are Rubbed Together

It was found centuries ago that these materials: wool cloth and paraffin wax, glass rod and silk cloth when rubbed against each other attracted one another. While two glass rods when rubbed against ...
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3answers
1k views

What types of materials can be electrically charged by rubbing?

What types of materials can be electrically charged by rubbing? Is there a certain type of materials in which static electricity can be produced by rubbing together two different materials?
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4answers
4k views

Capacitor Charging and Discharging when connected to the ground

When we charge a capacitor using a battery and then remove the battery, the plates of capacitor becomes charged. One holds positive charge and the other one gets equal negative charge. o. k. ? Now ...