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

learn more… | top users | synonyms

0
votes
1answer
264 views

What does an increased time constant of a capacitor do?

If a capacitor is being charged to any voltage, what effect would increasing the time constant have on it and if a graph of Charge Q/Time T was plotted to give a positive decreasing gradient, how ...
-1
votes
2answers
54 views

Possiblity for particle to be carried by a wave such as a photon or electromagnetic wave/waves in general for means of transportation/travel? [closed]

I am wondering whether it is possible for a photon/EM wave to carry a very small particle like an elementary particle or smaller on it like a highway carries a car traveling on the highway or an ocean ...
8
votes
1answer
221 views

Physical interpretation related to a non-linear partial differential equation

I am doctoral student in pure mathematics working on a particular problem. My question is if this problem has applications to real world phenomena. I will try to explain the direct problem starting ...
3
votes
0answers
40 views

Geometric frustration in power transmission networks

I read this article concerning the detection of Braess Paradox on power transmission networks: http://phys.org/news/2012-10-power-grid-blackouts-braess-paradox.html Here is a quote from the article: ...
1
vote
0answers
19 views

What happens to metal when exposed to an electric current for an extended period of time?

I was wondering what happens to the actual metal (copper, aluminum, silver, gold) when electricity is ran through it for a long period of time. Say years like the wire in a house. Does the ...
0
votes
1answer
686 views

Comparison between current and voltage sensitivity

Current sensitivity of a galvanometer is defined as deflection per unit current, $$\frac{\phi}{I}=\frac{NAB}{k}$$ Here, $\phi$ is the angular deflection, k is the torsional constant of the spring, ...
1
vote
2answers
189 views

Microscopic fields inside a conductor

In a neutral conductor if we assume electrons as point charges, the electric field in the space between them cannot be identically zero. This microscopic field may be very weak. What if we were very ...
0
votes
1answer
127 views

How is a variable potential divider able to reduce current/voltage through a component to zero, unlike a variable resistor?

For example, the diagram in my text book shows a filament lamp, in series with a uniform resistive wire, which can have its voltage and current varied by moving the sliding contact, e.g., a ...
0
votes
0answers
30 views

Bulbs glow with different brightness in one arrangement and the same brightness in the other arrangement

The question is: Mr.X decorated his house with fairy lights on a celebration.He bought 40 bulbs and operated at 220V. He found all the bulbs are glowing with different brightness. He called his friend ...
12
votes
2answers
1k views

Why does a cathode have to be heated to emit electrons?

Considering that electrons are highly mobile inside of a metal, why do they have such a tough time getting out at the edge of it and continuing their trip ballistically?
0
votes
2answers
387 views

Magnet dimensions for 3-phase permanent generator

I'm making a 3-phase permenant generator. According to Faraday's law, the emf produced is negative number of turns times the change in magnetic flux over the change in time. If it is only the CHANGE ...
3
votes
2answers
177 views

Question regarding Van De Graff generator Belt

I have made a VDG generator with a rubber band as the belt and a glass roller. It doesnt seem to work because I think the rubber band may be conductive. I was thinking of using other materials for ...
-1
votes
1answer
33 views

Current carrying conductor

In a current carrying conductor, the net flow of charge is zero. Is this possible? Arent the charges moving? Are the charges moving in a current carrying conductor?
-2
votes
0answers
22 views

Charging Copper ball bearing

I want to conduct an experiment to observe the trajectory of charged particles in applied magnetic and electric field. Thus, I want to charge a copper bead/ball bearing. How can I electrically charge ...
0
votes
0answers
18 views

How do I calculate the effective resistance in this circuit? [closed]

How do I calculate the equivalent resistance across A and B when i) All resistors have a resistance in the given circuit of $~\mathrm{R }$? ii) The resistors in the given circuit have values as ...
0
votes
3answers
257 views

Why don't get I shocked in an electric shower if the resistance makes contact with water?

I've found this image that perfectly illustrates my shower. I've read somewhere that the resistance is insulated so even if it touches the water, it doesn't conduct. However, as you can see, the ...
0
votes
0answers
16 views

Tesla's radiant energy system [closed]

Would Tesla's radiant energy system work better on earth if there was no magnetosphere, and more radiant energy from the sun is able to reach the system? Thanks!
-2
votes
1answer
21 views

Potential Difference

Ohm's law: $$V=IR$$ Here $I$ is the current in the circuit, which is equal to charge flowing per unit time. $R$ is the resistance offered. $V$ is potential difference. What's the physical ...
1
vote
2answers
34 views

Trouble understanding Electric flux and gauss law

Well, i know that the electric flux is the number of field lines passing a certain area, but (1)what does that mean? I can't the concept itself. I know it have many applications, gauss law one of them,...
1
vote
4answers
2k views

Which of the following has higher resistance - milliammeter or ammeter?

The question is the same as the heading - Which of the following has higher resistance - milliammeter or ammeter ? Now my teacher's and my answers don't match. It is assumed that the spring constant /...
3
votes
1answer
44 views

Direction of AC current in a very long wire [closed]

Suppose an external wire of length 10^8 meter (very long indeed) is connected in between the slip rings of an AC generator externally. Taking the speed of current propagation to be ~10^7 m/s, then it ...
5
votes
0answers
32 views

Electron Beam does not appear to be continous (CRT Experiment)

https://www.youtube.com/watch?v=2xKZRpAsWL8 Why do you see patches of purple in the tube? Shouldn't there be continous lines of colour? As far as I know, you see the rays because some of the ...
1
vote
0answers
25 views

Why does static charge build up and how do I prevent it?

I bought my 11-month-old son a tricycle from Smart Trike (official website) and I have noticed that after a few laps indoors on my marble floors static charge would build up in him as I can see his ...
1
vote
1answer
33 views

Is a straight lightning bolt possible?

Recently, I saw a demonstration where an annealed steel rod and a hardened steel rod were made to fail from tensile stress (they were pulled on like an elastic band and snapped in a vice-like machine) ...
1
vote
1answer
33 views

What is the average range of voltage of lightning in sky?

I wondered how much energy is required to produce , such a loud sound? What is the average range of voltage in sky? Is there any possible way to store it ,and use when needed?
-1
votes
1answer
41 views

What is the maximum amount of electricity I can draw in 48 hours from a domestic supply? [closed]

An electricity company is offering free electricity for a 48 hour period every week. The rate the rest of the time is very expensive. How much power can be drawn from a domestic UK supply? Would it ...
1
vote
2answers
64 views

Electrical equivalent of inverted pendulum

Background I am working on a summer project to design labs for undergraduate students. One of the topics is feedback and there is already quite a lot of stuff about passive feedback, so we might add ...
0
votes
1answer
30 views

Energy dissipation in current flow

In section 4.8, Energy dissipation in current flow, of Purcell and Morin's Electricity in Magnetism, the expression for the power expended by a resistor is derived. The sections includes the following ...
2
votes
3answers
210 views

What can justify the decrease of the electrical conductivity with the increase of light intensity?

I have currently been working with a sample that "appears to" decrease its resistance when I cover it and protect it from light. Basically it presents the opposite behaviour of a photoresistor. What ...
8
votes
3answers
790 views

Is there an electric field around neutral atoms?

Even if the atom is neutral (equal numbers of protons and electrons), the electrons and nucleus form an electrical dipole, so there is still an electric field around them, even though the total charge ...
2
votes
5answers
38k 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 ...
0
votes
2answers
623 views

Do electrons lose energy between the battery anode and cathode?

In a battery circuit, does an electron leaving the anode carry more energy with it than an electron returning, from having been through a machine, to the cathode? If not, how does the battery deliver ...
0
votes
1answer
146 views

Basic concepts of electrostatics

How to deal with a grounded conducting sphere (I.e finding charge on it) in uniform electric field ? And if any two charged conducting spheres are in each other's electric field then will ones field ...
-2
votes
2answers
90 views

Can Light Really be Matter? [closed]

I remember during my early education being taught that light is a form of matter. This has always seemed counter-intuitive to me.
1
vote
0answers
21 views

How pseudocapacitors work?

I have read that pseudocapacitors are combined of a carbon electrode and a metal oxide one. On the carbon electrode simply a double layer is built up and on the other some chemical actions(redox) ...
-1
votes
1answer
43 views

Why Electric current is considered fundamental quantity [duplicate]

It seems to me electric charge is more fundamental than electric current. Can anybody explain why electric current is taken as fundamental quantity and not electric charge?
1
vote
1answer
117 views

Force on a magnetic dipole due to a magnetic field

Imagine a solenoid which has current $i$ and is producing a magnetic field $B$ which equals $$B=\mu N i$$ Now, imagine we put a small cylindrical magnet at the end of the solenoid. Then because at ...
14
votes
3answers
945 views

How did physicists know that only negative charges move?

I have phrased similarly another question about how physicists knew that two charges exist, positive and negative. The purpose of the question is not necessarily to educate me historically. It's just ...
1
vote
0answers
107 views

Is it possible to transform chemical energy in electrical energy by modifying the equilibrium constant?

Considering a Daniell cell, is it possible to create endlessly electrical energy by using atmospheric temperature (for example) variations to modify the reaction's equilibrium constant ? I apologize ...
1
vote
1answer
104 views

Static electricity and insulators

I've read that Stephen Gray in his experiments on electricity, he has found that static electricity can be conducted -transferred- through an insulator thread made of silk. So, how could that happen ...
0
votes
2answers
55 views

What does an oscillating magnetic field produce? [closed]

An alternating current produces a magnetic field. A oscillating charge produces light, which is an oscillating electric, and magnetic field mutually perpendicular to each other, and their motion is ...
2
votes
1answer
147 views

How do the different types of energy apply to voltage in a circuit

I was just wondering what happens in a circuit in terms of different types of energy transformations. If you apply a voltage to a circuit then electrons start moving (very slowly). Since the electrons ...
2
votes
1answer
25 views

Is potential difference the difference in electric potential energy or electric potential?

Referencing the book Physics for Scientist and Engineers, Ninth Edition, the book says that "Potential Difference should not be confused with Difference in Potential Energy." I also reviewed several ...
2
votes
3answers
194 views

Can pulsating DC current be transformed?

Since pulsating DC current is changing, why doesn't it induce a changing magnetic flux in the transformer core? Is it able to induce a transformed current in the secondary coil?
6
votes
5answers
15k views

Potential difference (PD) and electromotive force (EMF) in terms of electrons?

I am trying to understand potential difference and electromotive force in terms of electrons. In the above 3 circuit diagrams the red shows (what I think to be) the distribution of electrons around ...
0
votes
1answer
40 views

Why does the heating cord not glow while the heating element does?

This question was in our textbook: 'Why does the heating cord of an electric heater not glow while the heating element does glow when electric current passes through it?'. All I have been taught is ...
36
votes
5answers
5k views

How did physicists know that there are two kind of charges?

Problems The question I am about to make is either too stupid or hasn't bothered anyone because its obvious because I can't really find the answer anywhere. I am currently studying electricity and ...
1
vote
1answer
30 views

How does isolating transformer protect from geting shocked

From what i know, isolating transformer makes it that you would have to touch both ground and phase cables to get shocked, but why exactly is that. There should be some potential difference between ...
-2
votes
1answer
47 views

Find the electric field of a uniformly polarized sphere

The problem statement, all variables and given/known data We want to calculate the field of a uniformly polarized sphere of radius=R Relevant equations $$V(\vec{r}) = \frac{1}{4 \pi\epsilon_{0}} \...
9
votes
9answers
650 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 ...