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

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Why do bulbs dim when we switch on TV?

Why do the bulbs dim for a moment when we switch on equipments like CRT television or water pump?
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0answers
16 views

electrostatics and current electricity

What is the relationship between a closed and open circuits with electromotive force.electromotive force is the force that keeps charge moving in circuit when a potential difference is created.
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3answers
20k views

Why don't electric fish shock themselves?

Fish like electric eels and torpedoes have specially designed nerve cells that allow them to discharge hundreds of volts of electricity. Now, while pure water is usually nonconductive, the dissolved ...
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3answers
52 views

Is it possible to avoid static electricity? [closed]

Sometimes I touch a car or a door and I feel the static electricity in my hand and it hurts sometimes. I try not to touch anything because I feel like I am going to feel this pain again. Is there a ...
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1answer
35 views

Charging with No Current

This may be a basic question, but I am not sure about the exact reason, so I'm asking this I've noticed quite a few times that when you plug an iPad charger to a socket and then switch it on, then ...
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1answer
61 views

why do light bulbs explode when in contact with water?

Is it true that when water pours on a light bulb it will explode? If so does this apply to all light bulbs and how does that happen.
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1answer
43 views

Does a capacitor experience a Newtonian reaction when being charged?

Say I have a capacitor that is being charged with a battery. There are two wires, one on the positive and one on negative terminal of the battery which go to a capacitor. During the charging, a ...
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1answer
29 views

Equation relating voltage and minimum rpm needed for generating 1V using a magnet around copper wire

I was wondering if there is any equation or law or something that relates the minimum rpm needed when a magnet spins around a copper wire to generate 1 volt? In other words, how fast does the magnet ...
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0answers
29 views

Difference between potential difference and electromotive force [duplicate]

What is the difference between potential difference and electromotive force? Potential difference is the work done when 1 Coulomb of charge move one region to another.
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2answers
60 views

Ohm's law experiment

I was going through my physics laboratory manual. In the Ohm's Law Experiment, the book states a few precautions without any reasoning. 1.The wire whose resistance has to be determined should ...
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2answers
66 views

How can “…electrons flow in metals, but not in the ground…” explain grounding rods?

I really enjoyed Why is the charge naming convention wrong? But, in the comments at the very end, the statement that "...electrons flow in metals, but not in the ground..." left me uneasy. I was ...
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2answers
90 views

How does a point charge interact with a Gaussian surface?

A spherical Gaussian surface encloses a point charge $q$. The point charge is moved to to a point away from the center of the sphere. Does the electric field at a point on the surface change? ...
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1answer
88 views

Why does energy flow between a high voltage transmission line and linemen approaching it on a helicopter?

The video High power line workers shows linemen servicing a live high voltage transmission line. As the helicopter approaches the line, the lineman reaches out with a metallic wand that is ...
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1answer
59 views

Why is a series resistor needed in a simple thermistor experiment? [closed]

I have come across the following simple question, however I can't see any need for a fixed resistor in series. The only possible reason that I can think of is that the resistance of the thermistor ...
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0answers
20 views

Capacitor charge and current as a function of type question [closed]

Two capacitors, one resistor and an ideal battery are connected through switches s1,s2 and s3 as shown in figure. Initially capacitor of capacitance 4C is charged, while other is uncharged. The upper ...
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1answer
34 views

Resistance of a general resistor [closed]

I have some medium with a resistivity which depends on position. In this material are two electrodes, is there an integral or something which i could numerically integrate to find the resistance ...
2
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1answer
2k views

Can sound produce electricity?

Energies of wind and water can produce electricity. But, can sound energy also be used to produce electricity?
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2answers
326 views

When two spheres of equal charge make contact, why does the larger sphere gain more charge?

Suppose that two spheres, $S1$ and $S2$, with radii $R1$ and $R2$ resp. have the same charge uniform charge $Q$ and $R1 > R2$. After they are forced to come in contact, why does $S1$ gain more ...
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1answer
30 views

If we increase dimensions of a wire, how does electron density change?

If we increase the diameter of a wire, does the electron density change at all? When we increase the diameter or the length of a wire (while solving numericals) do we add appropriate number of ...
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1answer
109 views

If increasing applying energy to an atom excites electrons, why does electrical conductivity decrease as temperature increases?

Applying energy to an atom makes the electrons jump up to higher energy levels. This is known as excitation. Electrons on higher energy levels are easier to remove from an atom than those on lower ...
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1answer
33 views

I need proof for dW=eIdt [closed]

I need help to understand from where this equation is formed inorder to continue to study energy stored in an inductor.
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1answer
66 views

Why doesn't a fluorescent lamp implode even though the pressure difference is very high?

According to Wikipedia, the pressure inside a fluorescent lamp is 0.3% of the atmospheric pressure, so the pressure difference between the outside and the inside of the lamp is almost equal to the ...
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9answers
21k views

Why is the charge transferred by electrons and not by protons?

Charges are transferred by electrons which we all know. But why can't it be transferred by protons? Well, I searched on Google where I found similar questions already being asked on many sites. ...
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1answer
88 views

Does temperature have any effect on static electricity?

This is one of those questions that came up during a discussion with a friend on static electricity. His argument (which I dispute) is that there must be a relation between temperature and the ...
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49 views
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How to apply kirchoff's laws to motors in DC and AC settings

DC case: is it ok to treat a motor as a variable resistor, with resistance depending on the load? AC case: suppose I have a motor that runs at 120V AC and is rated to X watts, how can I determine how ...
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2answers
88 views

Some questions related to circuits and flow of electrons

I have some doubts related to electric fields and flow of current. So, let us assume an electric circuit, which contains a battery and a wire connecting positive and negative terminal of the battery. ...
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2answers
5k 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 ...
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1answer
53 views

Why are there no charges inside a conducting sphere?

Why is it necessarily true that all charges occupy themselves only on the surface of a conducting sphere, and not anywhere inside the sphere? One argument is that if a charge were to be inside a ...
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0answers
38 views

How to increase Resistance of a conductive material?

I'm working on a project that I should measure the resistance of conductive sample ( like brass ). But I've a problem. Resistance of conductive samples is too low which requires a miliohm meter to ...
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0answers
25 views

Efficiency of resonant inductive coupling as a function of distance

What is the relationship between the efficiency of energy transfer between resonant inductive coupling between two coils, and the distance between the coils?
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8answers
442 views

How do electrons know when a circuit is closed?

I was told that electrons do not begin flowing unless the circuit is closed. The electrons from the battery are not in the ends of wire when it is open, apparently, as there is no reason for them to ...
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2answers
46 views

What is meant by “current” in this context?

This is a quote from Optics by Hecht: A stationary charge has a constant E-field, no B-field, and hence produces no radiation—where would the energy come from if it did? A uniformly moving ...
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2answers
31 views

Confused about two formulas for electric field magnitudes

So I am going through my notes and I come across these two equations which both describe electric field magnitudes (I think.) $$\frac{k q}{r^2}$$ and $$\frac{Q}{A \epsilon_0}$$ Could someone ...
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4answers
8k views

Does Fire Conduct Electricity? Why?

Recently, I have stumbled upon a YouTube video by Veritasium describing the conductivity of fire. My question is: how exactly does fire conduct electricity? I am a high school student; therefore ...
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0answers
45 views

Force Exerting on a magnetic train

A question is already asked ( How does this “simple” electric train work? ). But I've got a question about it. In order to calculate the force which is being exerted on the system including magnets ...
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0answers
20 views

How do electrons choose their way through nodes? [duplicate]

Suppose I have a circuit, powered by some emf ($V$). If I put two resistors $R1$ and $R2$ of different resistances in parallel, the current at the node is divided following Kirchhoff's circuit laws. ...
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45 views

Van der pauw method for an isolated hole

Van der pauw method is a way to measure the resistivity of a material with arbitrary shape while it meets some specifications ( being homogeneous and ...). One of the conditions is that the sample ...
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1answer
24 views

Do we need wires for current conduction in ionosphere?

As we all know in ionosphere there are free ions and electrons present. So if we somehow take a bulb and a battery in the ionosphere then will the bulb glow due to conducting nature of environment ...
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4answers
64 views

Electrons flowing through a circuit make it warm, where does that heat come from

in a circuit I have a low resistance device that consumes many watts, in normal operation this device will get warm; where does this heat come from? the law of conservation of energy states that the ...
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0answers
39 views

How to figure out if an element in a circuit is absorbing or delivering power?

. Eg: In the above circuit. 50v source and 0.2Va current source is said to absorb power.If power is absorbed,what work is done with the absorbed power.
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2answers
172 views

Why isn't the magnitude of the electric field in a circuit zero?

I've been re-reading my knowledge of circuits and how current flows as well as the surface charge distributions in the steady state, since it's been quite some time and we've just started studying ...
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0answers
91 views

Which scientist is this?

Okay so I was watching discovery channel, in that i saw a man cleaning live electric wires of 10k volts in the air, he was not touching the ground. They said he was able to do this because of the ...
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2answers
36 views

Electrical injuries - Doorknob vs powerline

This is something that has bothered me since high school physics. I have a medical and engineering degree, yet I can't for my life answer this question in a way that's logically consistent in my ...
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3answers
111 views

What changes in the electrons before and after a voltage drop?

It is easy to visualize gravitational potential energy as a function of the position of height, and a change in this potential is manifested in a change in height. Further, by the work-energy theorem ...
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0answers
33 views

What do we mean by live and neutral wire? [duplicate]

In our household circuit we have ac supply of 50 Hz. It means current reverse its direction in every 100th second. I think then, current flows in one direction then another.Then, why do we have live ...
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2answers
45 views

which is efficient on solar electricity by photo voltaic or thermal

As we know solar energy used to generate electricity in two major ways: photovoltaic and thermal energy. The most small applications or personal use are mostly using solar cells. But when it comes to ...
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0answers
22 views

The frequency induced by the alternating current

Let set up the experiment as followed. A string is stretched at two ends. Two magnet poles N and S are placed under and above the string. Now we let an alternating current go through the string with ...
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1answer
49 views

Electric field along a wire and load

I have referred to many books and all of them apply loss in potential across a resistor only in case of circuits. However, the electric field is present in the whole conductor. Hence the electrons ...