Questions tagged [electrical-resistance]

The tag applies to electrical resistance and resistors. DO NOT USE THIS TAG for non-electrical resistance.

239 questions with no upvoted or accepted answers
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6
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1answer
195 views

Chemistry of electrical conductivity of pure water

I understand the electrical conductivity of pure water is very low, but not zero, and is due to the slight number of H+ and OH- ions naturally present. I understand that they will move under the ...
5
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1answer
128 views

Is electricity perpetual in a superconductor system?

I wonder if electricity consumption happen according to the Law of conservation of energy and Joule effect, in a regular circuit certain amount of energy is transformed into heat by components ...
5
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1answer
358 views

How uniquely determined is the impedance of an infinite-chain circuit?

A recent question asked how to find the impedance of an infinite chain of series-plus-parallel circuits. The standard trick is to split the chain after the first link, and treat the tail of the ...
4
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0answers
119 views

What is the physical reason behind the negative differential resistance (NDR)?

As you know, there is an effect called negative differential resistance in some electric devices and materials, but I could not find any article or book or any other reference to talk about the ...
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0answers
140 views

Can the Hall effect drive a current?

In the Hall Effect current is passed through a wide strip of metal in a perpendicular magnetic field. Since (some of) the negative charges in the metal move but the positive ones stay put, the ...
4
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0answers
77 views

How can the effects of temperature be accounted for in-situ electrical resistance corrosion monitoring?

In reading the Berkeley Lab's article Rust Never Sleeps, where research is underway investigating the use of iron oxide rust as a photovoltaic, they state: Rust – iron oxide – is a poor conductor ...
3
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0answers
137 views

Detect ions in water using impedance spectroscopy

I would like to check the presence of Na, Ca or other ions dissolved in water using impedance spectroscopy. I was thinking that because the ions have different masses they will have different ...
3
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0answers
226 views

What is the mechanism for graphene to conduct so well?

If metals have always been the best conductors, what is it about graphene that makes it such a good conductor in the plane? Specifically, in the metals silver is better than copper. I always assumed ...
3
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4answers
1k views

Electromagnetic field and voltage drop in a circuit

I have been thinking for a while about what really causes voltage drop and how to explain it in terms of what the electric and magnetic fields do. So I've been reading a lot of posts here and in other ...
2
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1answer
84 views

Resistors parallel to short circuit

I have a trouble solving this problem. (Actually, each resistor is not parallel with the bottom wire since the voltage across each of them is different with that of wire.) In the manual, the bottom ...
2
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0answers
82 views

What's the explanation for Kohler's rule?

In a metal, the increase of resistivity ($\Delta\rho$) due to an applied magnetic field follows a functional form of the parameter $\rho_0/B$ (residual resistivity divided by magnetic field) i.e. $$(\...
2
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0answers
35 views

Would there be any current if an electric circuit is cooled to absolute zero?

My question is if I got a superconductor and cool it to absolute zero at least measurable by today's tool, it should have no electrical resistance but then would there be any current when there is a ...
2
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1answer
344 views

How resistance in coils affects the damping of oscillations of a magnet through them

I performed an experiment where I connected a magnet to the end of a spring with the north side on the bottom. The magnet at the tip of the coil was aligned to pass through a column of coils of about ...
2
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0answers
31 views

Interpretation of operators applied to systems with higher symmetry

Let me make an example from solid state physics to show what I mean: We can show that for a 2D hexagonal lattice the resistivity is isotropic by noticing that the resistivity tensor is symmetric ...
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0answers
138 views

In series RLC circuit, does decreasing the capacitance value really make the circuit more capacitive circuit?

This seems very counter intuitive to me. How can decreasing the capacitance value make the circuit more capacitive ? The math tells me so : If $C$ decreases then $X_c = \dfrac{1}{\omega C}$ ...
2
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0answers
80 views

Input impedance of a line with complex load

I am currently studying electromagnetism mostly with the help of the book "Microwave Engineering" and when trying to solve problems which main goal is to compute the input impedance of a lossless ...
2
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0answers
747 views

Umklapp Scattering of electrons by phonons

Kittel has a figure in his Solid State text in the free electron chapter depicting the scattering of electrons from phonons. He explains that, if an electron (with, say, $k=4\pi/5a$) scatters out of ...
2
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0answers
297 views

Approximating the equivalent resistance of a large resistor network

Per the elegant solution of this Phys.SE question we can find the equivalent resistance between nodes $k$ and $l$ of a resistor network like this: $$R_{kl} = {{\rm det}A^{(kl)} \over {\rm det} A^{(l)}...
2
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0answers
69 views

What if in potentiometer, the loops are not balanced to cancel the potential and current flows?

As described in the book (image) that loops should be balanced with equal potential with help of the galvanometer. What if the we do not balance it to zero and have some current flowing? Can we still ...
2
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0answers
103 views

Calculating the electrical conductivity of a metal nanostructure

The general system is shown in the following picture. There are two electrodes and a potential applied to them, so there is current flowing in the system. The electrodes are connected with an ...
2
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0answers
435 views

Sensitivity of Wheatstone bridge

I was going through my textbook and it told me that the sensitivity of a metre bridge is maximum when the resistances in its arms are equal (at balanced conditions) and for a potentiometer if the ...
2
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0answers
122 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 ...
2
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0answers
802 views

Negative resistance temperature coefficient of metals

How is it explainable that some metals have their electrical resistance increased while other metals act the other way? When the temperature of a metal rises the molecules move faster and from my ...
2
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1answer
62 views

Why is low resistance beneficial to ion exchange membranes?

http://scitation.aip.org/content/aip/journal/jcp/139/11/10.1063/1.4821161 The article states that the graphene filter has a much lower electrical resistance than existing ion exchange membranes, ...
2
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0answers
182 views

How do I determine resistivity from electron defects of high purity gold?

I am trying to create a plot for the electrical resistivity of high purity gold from 1 K to 1000 K. I found gold's resistivity at 300 K using the Wiedemann-Franz Law based on thermal conductivity data ...
2
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0answers
207 views

Is my method of calculating thermal conductivity of a metal wrong?

I am trying to determine the thermal conductivity of pure copper at various temperatures using the Weidemann-Franz Law but for some reason it is not matching up to textbook data. I used the Bloch ...
2
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0answers
89 views

sensitive scale & resistance of analog current meter

Does the resistance of an analog current meter increase or decrease when it is set to a more sensitive scale (lower range)?
2
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0answers
265 views

The origin of contact noise?

I was trying to measure the noise of a device with metal probes. I was not sure whether I should trust the results because I was told contact noise might contribute to some degree. I am a little ...
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0answers
8 views

“Directional” conductivity in linear flux-potential laws?

Question: Has the notion of "directional conductivity" been defined and used in the study of heat flow and electric current flow? Context: The table below gives three laws that describe linear flux-...
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0answers
38 views

Potentiometer's working

I know that in a closed circuit with multiple batteries, current is provided by the battery which has the maximum voltage. Let's suppose that $E \gt V$. Now, the voltage $V_b$ at point $b$ will ...
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3answers
76 views

Why voltage is same across parallel resistance?

Since voltage stands for energy per unit charge to be used to carry it from one point to another,why should energy per unit charge be same for two resistors of different resistances,?the energy ...
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2answers
40 views

Resistance between steel wires in water delayed response

I am trying to make a wire wave gauge by measuring the resistance between two stainless steel wires. Theoretically, the output voltage reading should change the deeper the wires are in the water. If ...
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0answers
32 views

Temperature Dependence of the Kubo Formula

I'm trying to calculate the DC conductivity of a Renormalized Fermi Liquid with Green's function \begin{equation} G(i\omega,k)=\frac{Z}{i\omega-Z\tilde{\epsilon}_k-ig\omega^2} \end{equation} where $...
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0answers
27 views

Resistors equivalent using symmetry and equipotential line

I propose the following statement: In a circuit, while determining equivalent resistance across two points, if the circuit is symmetric wrt the line joining the two points , we may fold the circuit ...
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1answer
36 views

Relationship between concentration and resistance of aqueous solutions

I'm a senior physics/chemistry student working on a practical assignment where I am trying to identify the resistance of CuSO4 in solution (distilled water). I have recorded my data and determined it ...
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3answers
105 views

RC circuit discharge while being connected to a battery?

I am facing a conceptual problem in analyzing the following situation which was part of a physics exam; A series RC circuit with $R = 200k \Omega$ and $C = 10 \mu F$ is connected to a 5V battery and ...
1
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1answer
33 views

Nillsons Electrical Circuits Confusion

I'm reading this book Nilssons electrical circuits and I'm beginning to get frustrated/confused on some of the circuit diagrams. For instance this simple circuit with resistors in series. I understand ...
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1answer
59 views

How to calculate acoustic impedance of a megaphone

I'm working on a physics problem that asks how a passive megaphone (simple cone shape) can optimise the transfer of the human voice, compared to not using one at all. I understand that some of this is ...
1
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1answer
29 views

Resolve The Envelope Detector Circuit

I was working on a little project and I was wondering if the envelope detector circuit could be resolved analytically. Let me explain. The circuit is the one shown above, I know the values of $C$, $R$...
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0answers
87 views

Elementary argument that Ohm's law is nonclassical?

The freshman physics texts that I have to hand (Purcell, Feynman lectures) seem to invoke Ohmic behavior of materials without explicit justification in terms of microscopic models or experiment. ...
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1answer
112 views

Nordheim Theory for resistivity of alloy

Is there any information on the actual number of Nordheim theory? A paper I found says, the resistivity of a binary alloy follows, $$\rho=x(1-x)(V_a-V_b)^2 $$ ,where $V_a$ and $V_b$ are "potential", ...
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2answers
63 views

What is the voltage in electrical circuits?

I understand what the voltage is and I realize that the battery makes an electric field due to the accumulation of the charges in the anode and cathode this electric field causes electric potential ...
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2answers
85 views

How could a bulb light up if aĺl the voltage is lost in the resistor?

I recently came up with this slight confusion about voltage loss in resistors/resistance. So for example My circuit has a 12V battery, a 2 Ohms resistor and a Bulb. If we use the V=I.R formula then a ...
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1answer
121 views

What does it mean if the resistance of a semiconductor increases due to light?

I have synthesized an $n$-type semiconductor material $\text{ZnO}$. Under light illumination, its resistance keeps increasing. What are the reasons for this?
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0answers
170 views

Definition of Ohmic bath and damping force

I have read the Wikipedia article on quantum dissipation where it is talking about the bath spectral function. The bath spectral function provides a constraint in the choice of the coefficients $...
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0answers
111 views

Electrical resistivity calculation of a cylindrical material

I have a copper rod, its diameter is 13mm, and its height is 13mm. I want to check its electrical resistivity. I have tools to give this copper a constant current by two points (the two black dots in ...
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1answer
117 views

Parallel voltage source concept

I am having doubt understanding this: If two voltage sources V1 and V2 are connected in parallel with different voltages like 2v and 3v is it possible or the scenario is wrong. An example is this ...
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1answer
83 views

Why does simplifying resistance networks give the right answer?

In the circuit$\hspace{150px}$,why is it true that if we simplify the parallel combination as a resistor with an effective resistance of $R/2$ and then use series for $R/2$ and $R,$ it satisfies the ...
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1answer
69 views

Current through a metallic conductor

When battery is not connected to conductor why there is no heating effect while electrons are having very high kinetic energy? I want to know what happen in such a case What would be the resistance?...
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1answer
93 views

Hydraulic analogy and pressure in pipes

In the latest days I've been quite obsessed with understanding how electricity work through the hydraulic analogy. I still have some problems regarding how "voltage drop" works, and how pressure drops ...