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

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2answers
707 views

How is the current flow perpendicular to the wire?

This answer gives a great explanation of how surface charge builds up to force the current to move perpendicular to the wire: http://physics.stackexchange.com/a/102936/41086 However, it fails to ...
4
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1answer
506 views

Question about superconductivity

A long cylinder of radius $R$ is made from two different material. Its radius $r<r_0$ $(r_0<R)$ part is a material with superconducting transition temperature $T_1$, and its $r_0<r<R$ ...
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1answer
39 views

Even when the drift velocity of the electrons is very small, how is current in the circuit established immediately?

So I have this question in my textbook and Ive also got it in my test. Ive written a wrong answer. My friend wrote the drift velocities of each particle add up and he got full marks. Is it right? Can ...
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1answer
29 views

Earthing, neutral and Earth's conductivity

Ok so this is gonna be a lot of mini-questions. What exactly is the neutral wire? How does earth conduct electricity for a live AC mains even though its just dirt and stones (it should be an ...
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2answers
174 views

Charging by induction

When we charge an conductor by induction and grounding, we first bring a negative charge to the conductor. As a result the mobile electrons of the conductor get repelled and stay far from the negative ...
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1answer
1k views

Electric field from conductive to dielectric media

I am interested in the main difference between transitions from electric fields from Conductive to Conductive/ Dielectric to Dielectric and Dielectric/Conductive media. What are the boundary ...
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2answers
143 views

Why does a battery die more quickly when more resistors are added to the circuit?

I will be explaining what I think: A battery acts like a pump which provides energy to do work on negative charges to move them towards the negative terminal, and hence creating an electric field. ...
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0answers
25 views

What difference does it make if the turns in a tesla coil overlap?

Would a tesla coil in which the primary coil is made by overlapping the turns of the wire work?
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4answers
79 views

Which makes for a better equivalent capacitor? In series or in parrallel? [on hold]

I understand how capacitors in series and in parallel work. However, I am wondering if it makes a difference, in terms of making a better capacitor that can store more charge, would you connect them ...
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0answers
26 views

Electric circuits [on hold]

I could not figure out why my right lateral tight thigh just above my knee was slightly was irritated in I strange way. It was not a deep pain in the muscle and it could be rubbed away but it ...
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2answers
185 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 ...
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1answer
1k views

Why isn't ice a good electrical conductor?

Water can conduct electricity, and some solids can conduct. Why can't ice? Are ice molecules too packed together to let valence shell electrons bounce across each other to create electrical charge? ...
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0answers
26 views

Do wires have a potential difference? Why? [on hold]

I just want to know: do all conductors have potential difference? What about wires or bulbs specifically? Where does this difference lie?
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1answer
11 views

How do ink droplets passing through two charged metal plates become charged as well?

In the working mechanism of an inkjet printer, I came to know that ink droplets in the form of a stream pass through two charged parallel metal plates ( like a parallel plate capacitor) and while ...
0
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3answers
759 views

How is current produced in semiconductors or metals?

I think current is the movement of electrons through the wire or semiconductor, thus when I press the switch of the light bulb the electrons go from positive part to tungsten and light is produced. ...
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2answers
3k views

The electric field of a conductive sphere containing a charge - grounded vs not grounded

Let's suppose we have a sphere but unlike theoretical ones it'll have some thickness say $\Delta r$ and inner radius $R$. What I was wondering about is how will it behave if we place some charge $q$ ...
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1answer
200 views

Motion in insulating fluid under high voltage

I observed the following phenomenon in an experiment (I'm not a student of physics, just an amateur) and was hoping for an explanation. A metal pan is electrically grounded and a layer of ...
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0answers
193 views

Electric Honeycomb [duplicate]

Set a vertically oriented steel needle over a horizontal metallic plate. Place some oil onto the plate. If you apply constant high voltage between the needle and the plate, a cell structure appears on ...
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2answers
214 views

When potential difference is equal to the emf, isn't the current 0?

I have been told that the $emf$ is equal to the potential difference across the terminals of a cell when no current is flowing. Does that mean that the current is zero ($I=0$)?
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0answers
24 views

Strange roughness feeling on electrically ungrounded surfaces [duplicate]

When I have a device or a surface (typically metallic) that are not well connected to ground I feel a strange feeling when I pass (gently rub) my hand on them. Like the roughness of the surface is ...
0
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1answer
38 views

Possible reasons of electrocution in a good earthed appliance during sudden power off [on hold]

I was working in a industry. When I was using a machine, I felt slight electrical shock at the exact moment when the power supply went off. The machine is properly earthed. In spite of that I got ...
0
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1answer
259 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 ...
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0answers
19 views

What is the Direction of flow of electricity? [on hold]

I am actually confused about the flow of electrons , I had many questions regarding to this What constituted electricity ? In fact , What electricity actually is ? Does protons does not flow in ...
0
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2answers
372 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 ...
8
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1answer
205 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 ...
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0answers
32 views

Number of ions required to transmit a particular amount of charge [closed]

The question is as follows: 'If 0.035pC of charge is transferred via the movement of Al3+ ions, how many of these must have been transferred in total?' I converted the charge to coulombs (0.035x10-...
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2answers
55 views

Long life energy usage

I'm doing a project at school. I want to re-use energy. I know that it will not run forever (but I hope it will run very long). So I wanted to ask if the image below is right and I could use it at ...
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4answers
3k views

How does the movement of electrons produce radio waves?

I'm mostly wondering about radio frequencies. I understand that voltage is the movement of electrons, and that the antenna acts as a light bulb, emitting at radio frequencies, following the reverse ...
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0answers
16 views

help with equivalent resistance + thevenin [closed]

I'm trying to find the Thevenin equivalent. Here is the original: Here is the circuit to find Rth: I keep getting 12/13 ohms. The answer is 2 ohms and Vth is 60 V.
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0answers
22 views

About voltage sources in series [closed]

What is the reason of connecting batteries in series to obtain a higher voltage?
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0answers
21 views

Will I get marks for this answer? [closed]

It was a one mark question:- What does Joule/Coulomb represent? My answer:- Electric Potential. My teacher says that the answer is Volt. The question says what it represents, not the unit right? Is ...
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1answer
99 views

Does Maxwells equations imply $R=const*\rho$?

Suppose we have a resistor in a strange shape, filled with a medium of resistivity $\rho$, assuming only maxwells equations apply, is it true that R is proportional to rho, even for very low ...
0
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1answer
16 views

Is peak voltage or peak current kept constant when we change resistance in an AC circuit?

I found online that Ohm's law still applies to an AC circuit and that $V_{peak} = RI_{peak}$. However, I can't seem to find anywhere weather an AC source will : Act as a voltage source and keep its ...
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2answers
37 views

electric current

How can positive charges flow in current? I mean , we know that there is a particle called electron which can move but there is no such positively charged particle which can flow , there can be ...
5
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2answers
169 views

According to relativity theory, what is the force that two electrons moving radially apart exert on each other?

According to relativity theory, what is the most general expression for the force that two electrons moving radially apart exert on each other? I am looking for a function $$F(r(t)),$$ where $F$ is ...
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6answers
86k views

Why is AC more “dangerous” than DC?

After going through several forums, I became more confused whether it is DC or AC that is more dangerous. In my text book, it is written that the peak value of AC is greater than that of DC, which is ...
3
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3answers
4k views

How much energy was consumed when we turn on/off light?

My parents told me to turn off the light when I am not using it. But I remember my physics teacher told me that the action of turning on/off a light can cause huge energy. I am wondering how much is ...
3
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2answers
162 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
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1answer
22 views

Voltage in parallel and series connection

In series connection, voltage is said to be different and current constant across the circuit. How does it come about ? Is it due to the accumulation of electrons on one side due to resistors? Or, if ...
0
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2answers
721 views

What's the relation between output voltage and time to boil water given the same kettle?

An electric kettle rated 220V, 2000W needed 10 minutes to boil water when it is half filled with water in Singapore where the output voltage is 220V. Estimate the amount of time needed to do the same ...
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1answer
19 views

Armature of electric bell [closed]

I want to know that why is the armature of the electric bell made up of soft iron ? I googled this out and everywhere it was written that it is because of its propert to aquire electromagnetism but I ...
1
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2answers
3k views

How can be the neutral wire at 0 volts when current flowing through it?

Voltage is potential difference, and current flows because of voltage. So if the voltage is zero, how can current flow through the neutral wire.
7
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5answers
10k views

Why does the current stay the same in a circuit?

I was informed that in a circuit, the current will stay the same, and this is why the lightbulbs will light up (because in order for the current to stay the same, the drift speed of the electrons need ...
0
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1answer
120 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 ...