Questions tagged [electrical-resistance]

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

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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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135 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 ...
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76 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 ...
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133 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 ...
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220 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 ...
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49 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. $$(\...
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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 ...
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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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131 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 $X_c = \dfrac{1}{\omega C}$ ...
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75 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 ...
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704 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 ...
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284 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)}...
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68 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 ...
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100 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 ...
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390 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 ...
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120 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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783 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 ...
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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 ...
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206 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 ...
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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)?
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264 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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26 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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26 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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80 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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138 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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97 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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34 views

Why is an imaginary impedance compenent frequency dependent in a circuit?

And can we have a real frequency-dependent component or constant imaginary component to an impedance? My thoughts on the first question are that, an imaginary component to the impedance does not ...
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61 views

Spreading resistance of a microelectrode in a bath

I have a question regarding the spreading resistance, or series resistance, around a glass microelectrode in a bath (a conducting fluid with uniform resistivity $\rho$). The bath is grounded at a far ...
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38 views

How do I calculate the electrical conductivty of arbitrary semi-metal?

Assume that I have an Hamiltonian $$H=\sum_{k,\sigma}a^\dagger_k E(k)a_k$$ where $E$ is the dispersion relation with gap closing at some points. I want to calculate the conductivity of this system. To ...
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24 views

Designing capacitor or resistor systems where capacitor or resistor can bear limited voltage

A capacitance of $2\ \mu F$ is required in an electrical circuit across a potential difference of $1.0\ kV$. A large number of $1\ \mu F$ capacitors are available which can withstand a potential ...
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35 views

how to influence RH and air presure to resistance of air

For example higher RH (relative humidity of air) provide lower air electrical resistance. But how I can calculate with this relation? Moreover air pressure (between 1500 and 500 hpa) can influence ...
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92 views

Confused about the Drude model

I was thinking about the Hall conductivity, when this question popped up. If there is a magnetic field and an electric field perpendicular to it, then a Hall current is generated since the ions have ...
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29 views

Resistance in quantum transport

I know that due to quantisation condition of conductance: $$G = \frac{2e^{2}}{h}$$ The minimum resistance possible in nano scale channels is around 13k$\Omega$. This conductance assumes ballistic ...
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199 views

Infinite square grid of two different resistors

We have always heard about infinite square grid of identical resistors, in which the equivalent resistance is easly derived by simmetry consideration. However, how would we compute (or at least upper ...
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50 views

I-V curve of Zinc oxide film deposited on glass

Good day! I'm looking for any suggestion about my research. So basically my research is about electrical properties of ZnO film deposited on glass via spray pyrolysis. I want to determine the ...
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188 views

Multiple infinite ladders of resistances

I'm a bit stuck with this problem. I'll post the exact statement below: Consider the circuit given. Calculate the voltage across the 100Ω Resistor. The configuration of $I^{th}$ sub-circuit is given ...
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53 views

Is this Thevinin equivalent of a voltage divider, correct?

Found the PDF version of The Art of Electronics (Horowitz and Hill) recently, and, having nothing better to do... I thought I'd give it a read. It wasn't long before I hit a wall (courtesy: my inept ...
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23 views

Why Mobility Of Thin Film Changes With Deposition Temperature

A metal oxide thin film is a p-type semiconductor (say copper oxide Cu2O) due to metal vacancies in the film. This thin film can be deposited using some form of vacuum/vapor deposition. I know that ...
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616 views

A simple potentiometer problem

The question is given in the pic attached. Why should there be a change in the balancing length when the keys are closed for resistances $R$ and $X$ one by one? Shouldn't the potential between $A$ ...
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320 views

Why does resistance increase with potential at collector in the photoelectric effect?

In the photoelectric experiment, the graph of photoelectric current $I$ against potential applied at the anode/collecting plate $V$ looks something like this: When you apply a positive electric ...
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384 views

Negative imaginary part conductivity

Suppose we have some gas of electrons and we calculate the current as a response to an electric field. In linear response theory we would find in Fourier space $$ {\bf J}(\omega,q) = \sigma(\omega,q) {...
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44 views

Intuitive way of understanding quadratic magnetoresistance

Many papers that I have read regarding magnetoresistance in metals say that magnetoresistance should evolve quadratically with field. Apart from referring me to the Boltzmann transport equation, is ...
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249 views

Induced current by changing magnetic field and resistance

Let's say we have a wire loop with resistance $R$ in a changing magnetic field. The changing field will induce an electric field and hence an emf $\mathcal{E}$ around the loop. The induced E-field is ...
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33 views

Superconductors, batteries, and the cold?

I'm taking a calculus-based physics course: electricity and magnetism course. We touched on the concept of superconductors and how resistivity changes in relation to temperature. Everyone knows ...
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120 views

Practical application of the Drude model

I am trying to gain a better understanding of the Drude model. I understand that the Drude model is used to look at movements of electrons with in a material. My question is, what, if any, are the ...
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48 views

Negative Magnetoresistance from Frozen-Out Spin-Flip Scattering

A free electron gas would have zero magnetoresistance; it takes two carrier types to get ordinary magnetoresistance, which is always positive in sign. Beal-Monod and Weiner explain the negative ...
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95 views

Minus sign in analyzing RC with changing emf circuit?

I'm learning electromagnetism from Purcell's book. He say that if we have the following circuit: $$-\frac QC + RI = \mathcal E_0\cos\omega t~,\quad I = -\frac{\mathrm dQ}{\mathrm dt} $$ The ...
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573 views

Finding Inductance in an AC RLC Circuit?

In the laboratory you find an inductor of unknown inductance $L$ and unknown internal resistance $R$. Using a dc ohmmeter, an ac voltmeter of high impedance, a 1 microfarad capacitor, and a 1000 Hz ...
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399 views

Logarithm of the voltage of the inductor in RL circuit experiment is nonlinear with time

I performed an experiment about the RL circuit, with following circuit: (I used the PASCO RLC circuit lab.) By Kirchhoff's voltage law, (denoting the emf of the signal generator $\mathscr E$, ...
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397 views

salt water conductivity

my book says the following on conductivity in water with ions. I am confused about why electrons from the zinc (anode) repel positive ions. Because zinc becomes negative, shouldn't it attract it? ...