# Questions tagged [electricity]

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

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0answers
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### How are the electrons able to overcome the significant force of attraction of the ions?

The cause of electrical resistance(in a metal) is electrons colliding with themselves and the positive ions. So if the electrons collide with the positive ions, how are they able to overcome the ...
0answers
10 views

### Can I use a PWM motor regulator to control a LED string?

I recently bought some LED Christmas lights, but they are too bright. So I was thinking that maybe I could regulate the output by using a PWM regulator? My LED lights have an output of 30V from the ...
2answers
58 views

### Why do electrical current only flows when it is a closed circuit?

I know a typical setup for a closed circuit consist of a battery, resistor, a lightbulb and a switch but that's not important, the only thing matters is we closed the circuit so that there is a ...
1answer
19 views

### Calculating the wattage of an appliance with radial velocity of domestic electrical meter

There's a heater who's wattage I want to work out. I notice when it is not plugged into the mains socket, the dial on the electric meter for the house spins at x rpm. When it is plugged in, it spins ...
3answers
37 views

### What is the definition of direction of current?

Wikipedia defines the direction of current as: The direction of conventional current is arbitrarily defined as the direction in which positive charges flow. But suppose a region where there is a non-...
1answer
40 views

### Is it possible to measure the electric current speed through the wire by this method?

This method is very simple but I am not sure if it would provide accurate measurements.The current electrons deriving from the battery should have some speed and in that way should interact with the ...
0answers
10 views

### How to use Kirchhoff's voltage law on this circuit to calculate potential at point O? [closed]

In this circuit, I have to find the potential at point O. I tried using Kirchhoff's voltage law for the three open loops AOC, AOB and BOC to arrive at potential at O. According to my calculations the ...
4answers
398 views

### Do electrical appliances reduce the heating bill?

When you use an electrical appliance, most of the electricity used is turned into heat. Will the energy cost of using something like an iron be subtracted from the heating bill making it effectively ...
2answers
180 views

### Why is charge density depended from the distance?

If we suppose that we want to find the electric field at some point P. Let's consider a small volume element $\Delta V_i$ , which contains an amount of charge $\Delta q_i$. The distance between ...
2answers
29 views

### Thermal power station powered by temperature difference between high and low altitude air

Would it be feasible to build a system where warm air from sea level is pumped to the top of a mountain to power a thermal power station? With a lapse rate of ~ 1°C / 100 m there should be plenty of ...
3answers
54 views

### If the drift velocity of the electron is too low then how they can oscillate very fast in a high frequency alternating current?

As we know the drift velocity of electrons inside a current carrying conductor is $\sim 10^{-4}$ m/s and with this if it's an alternating current with a very high frequency let's say 10 kHz then how ...
0answers
11 views

### Can aurora (the geostorm) cause increased static electricity on the ground?

There was a G-1 storm last night and I had major static while taking off clothes, far more than usual. It was a clear night here not foggy like most places.
0answers
27 views

### Effect of one lightning on its consecutive lightning

When lightning strikes several times in one area, I wonder if the first lightning strike affects the next lightning. For example, when lightning strikes a point $A$, does the next lightning have a ...
3answers
4k views

### Does electricity have an associated entropy?

One can certainly measure entropy changes associated with the generation of electricity, but does electricity itself have an associated entropy (maybe related to voltage, current etc.)?
1answer
32 views

### Current produced by EM wave in circuit

I have a specific question regarding the current produced by an EM wave interacting with a simple square circuit with constant resistance $R$. Let's say the EM wave can be explained by the simple ...
2answers
182 views

### How to insulate static electricity?

This is a follow up question to Extending the reach of a crocodile clip for Kelvin Water Dropper experiment. We have resolved the issue, but now we have the following cable (in the image) that carries ...
2answers
37 views

### How does the high potential difference between the two points ionizes the air?

As we can see that for some instance air can tolerate the potential difference between two points without any high leakage current and when this potential difference between the two points becomes too ...
1answer
34 views

### Calculating total charge and energy transfer [closed]

How would you calculate the total charge and the total energy transferred in in this case?
1answer
204 views

### Demonstrate sinusoidal steady state in linear circuit

Suppose a linear passive circuit is hooked up to an AC generator which outputs a sinusoidal voltage of angular frequency $\omega$. How can we demonstrate rigorously that after a sufficient amount of ...
2answers
55 views

### What will happen if both electrons and positive charges got ability to move inside the conductor?

Let's consider a conductor which has a potential difference across its ends. And let's say that the electrons which already have tendency to move inside the conductor, by all of a sudden if positive ...
1answer
55 views

### Does the number of electrons colliding in wire get double as the length of wire gets doubled?

Does the number of electrons colliding in a wire get doubled when length of wire is made twice with its area of cross-section remain constant. My calculations for this are:- For wire of length $L$: ...
2answers
168 views

### Effect of electroplating on resistance

How will resistance of a wire be affected if I electroplate it with copper will it decrease ? And if yes then will the decrease be significant? I need to find a topic for my project I thought it might ...
1answer
15 views

### Why do gas discharge tubes operate indefinitely?(Or do they?)

Question Can a gas discharge tube with a perfectly sealed glass tube operate indefinitely? Or do the ions get "used up"? Further detail My (limited) understanding of gas discharge tubes is ...
2answers
56 views

### Alternatives to Steam Engines [closed]

Since the 18th century, humankind relied on steam engines to convert heat into electricity on mass scale even in fission and fusion （in the future） power plants. However, this process involves several ...
1answer
21 views

### Electric field inside a non-uniformly charged conductor

With Gauss's Law, if we take a uniformly charged hollow sphere for instance, the electric field inside the hollow sphere is 0 because there is no charge inside. However, what if this sphere is not ...
1answer
47 views

### How does emf depends on material of electrode? [closed]

Concise Physics mentions that: The emf (electromotive force)of a cell depends on 1) the material of the electrodes and 2)the electrolytes used in the cell.However it is independent of the a)the shape ...
5answers
2k views

### How does a resistor "know" to increase the potential difference across its ends?

My book says that current has to be constant throughout a simple series electrical circuit consisting of wires, a cell and few resistors, and hence resistors have higher potential difference across ...
3answers
161 views

### How does the battery create an electric field inside the conducting wire connected to its terminal?

In books, it is not explained exactly how the battery creates an electric field inside the wire. Also, is that the electric field inside the wire only or is it present outside the wire as well?
1answer
32 views

### What is the role of insulators in the accumulation of static electricity?

The Wikipedia article for static electricity says A static electric charge can be created whenever two surfaces contact and have worn and separated, and at least one of the surfaces has a high ...
2answers
51 views

### How can total charge be plus or minus?

I am a grade 10 student and in our syllabus we have electricity chapter. In the chapter the formula to measure the total charge of a body is: $Q=±ne \tag{1}$ Where Q is the total charge, $n$ is the ...
1answer
28 views

### Confusion regarding drift velocity and potential

From this post I understood that the drift velocity of electrons decreases further into the circuit. But my book says that electrons move with constant velocity throughout the circuit, and both of ...
1answer
70 views

### What does electricity have to do with physics? [closed]

As stated above, I've wondered why Electricity and Magnetism are part of Physics. Why are they part of it?
2answers
60 views

### Does a higher voltage always mean a higher electric field strength?

In a step-up transformer, the output voltage is higher than the input voltage, while the output current is lower than the input current. Basically, since P = VI is conserved, the current has to ...
1answer
1k 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 $r_0<r<R$ ...
1answer
464 views

### Why is lightning going from the Earth to the clouds while the electrons are going from the clouds to the Earth?

The lightning is often a discharge in advance. The (negative) charge slide occasionally a little further on in the conductive channel, wherein said channel is highlighted each time something. The ...
3answers
93 views

### Why can you shortcircuit a car battery with a wrench in your hand and stay safe?

In this demonstration by Prof. Walter Lewin a car battery is shortcircuited with a wrench. The experimenter is holding the wrench in its bare hands, so why he is not experiences an electric shock? ...
1answer
69 views

### EMF of source depends on the charge and the path then what do we mean when we say EMF of a source is $\epsilon$?

EMF of an EMF source (a battery for example) is defined as the work done by the non-conservative force(s) on charged particles as it passes through the terminals of the source divided by the charge of ...
2answers
46 views

### Changing magnetic and electric field

Does a changing electric field create 'constant' magnetic field or 'changing' magnetic And , does a changing magnetic field create 'constant' electric field or 'changing' electric field
2answers
99 views

### Many things that plug into the wall for power, use a transformer inside, so are not physically connected to the mains, do they consume mains energy?

Question Many things( hairdryers etc etc ) that plug into the wall / mains for power, use a transformer inside, so are not physically connected to the mains, do they consume mains energy ? I assume ...
0answers
10 views

### How does higher concentration leads to higher internal resistance in the cell?

Concise Physics mentions that: Higher the concentration of the electrolyte greater is the internal resistance(in a cell). I think that higher the concentration of the electrolyte higher would be the ...
1answer
28 views

### The current flow in a neon light tube aligned with a static electric field

If you put a neon light tube inside an electric field such that it is aligned with the field lines, it will start to emit light. This is caused by a current starting to flow inside the tube. This ...
2answers
153 views

### What is the physical explanation behind the decrease of open circuit voltage as temperature increases in an amorphous solar PV cell?

I have researched and looked at several papers describing the effect of temperature on the $I_{sc}$ and $V_{OC}$, and seen many numerical explanations as to why the voltage drops, with reference to I-...
3answers
639 views

### How come the number of wandering electrons is same as the number of the positive ions?

My book mentions the following: Cause of resistance : When an ion of a metal is formed , its atoms lose electrons from its outer orbit . A metal ( or conductor ) has a large number of wandering ...
2answers
67 views

### We know that $R={\rho l/A}$ but how do you define L and A, Area of cross section?

How do we define area of cross section of a conductor for resistance of a metal piece. When you a wire which is generally cylindrical you have a length of it. Its area of cross section is a circle ...
1answer
21 views

### How to make a simple DFAFC (direct formic acid fuel cell)?

So, I want to take some Formic Acid and make a DFAFC using it. I don't want something really complex, just something simple, and can turn on a light bulb. What metals will I need for the electrodes, ...
1answer
192 views

### Maximum practically possible current value for high frequency alternating current in metal conductor

Is it practically possible to reach 1 A current AC in the metal conductor with frequency 2 GHz? Or in other words, if I have plain metal wire, or maybe a thin tube/foil to reduce skin effect, what is ...
3answers
245 views

### Why EMF induced in the coil acts to oppose any change in the magnetic flux?

This might be an absurd question for some of you guys. According to Lenz's Law an induced current will create a magnetic field that induces another current in which it opposes the current causing it ...
3answers
537 views

### Where do the charge in a series/circuits (?) come from?

so I just entered the very (bemusing) area of electric charges in physics in my grade 12 syllabus and I am struggling. I've been able to do well with other physics concept, but when it came to ...
1answer
268 views

### Not enough current to supply load

Are there cases where a power supply can offer xV, which is required by a device, but be unable to supply enough current? For example, a voltage divider not only lowers voltage, but limits the ...
1answer
206 views

### Is the reason why a normal battery ran out of "juice" that it has reached electrostatic equilibrium between its two terminals?

If we connect a normal battery to a load circuit, its stored electric potential energy on its two terminals (+) & (-) will be consumed by work done on the load and eventually the battery is "...