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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22 views

Simplifying electrical circuits [migrated]

I have looked everywhere, but i can't seem to find a way to simplify this circuit. I wish i could tell you some of my ideas, but i'm really lost here, can someone help me? If you could explain how to ...
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2answers
373 views

Does direction of current in Node Voltage method circuit analysis matter?

I am trying to solve the following circuit using the node voltage method, but I'm having issues with figuring out how current is supposed to flow in and out of nodes. I understand that the current ...
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1answer
11k views

How to find the total current supplied to the circuit?

Recently, I came across a question based on finding electric current of a circuit. Here's the image... I know, by using the formula $I=V/R$, we can easily calculate the current as $V$ is given and $R$...
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249 views

Why is the residual-resistance ratio (RRR) a measure of good crystalline quality?

I am currently revising a paper on a few parameters of metallic Al, and it indicates that a higher RRR is a measure of good crystalline quality. My question is why would this be the case, if having a ...
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+50

Why to use non-inductive resistances in Callendar-Griffiths bridge?

Worsnop in his Advanced Practical Physics for Students states that All the resistances should be 'non-inductive', for in this method it will be seen that the galvanometer is permanently connected ...
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4answers
611 views

Current from Middle Battery in a Two-looped Circuit

With this question, as with many tutorials of similar questions I’ve found online, my textbook only mentions three currents: $I_1$, which flows through the left loop from and to the 19 V battery, $I_2$...
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24 views

What methods do I need to solve this? [on hold]

What methods should I do to solve (b)and(c) I can find answer (a) but I don’t know how to do with (b)&(c) I’m very appreciate if you can help me (This not my homework but I need to do for ...
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24 views

Power voltage relation

I have a question concerning the relation between power and voltage. We have a lamp with power of 36W when used with 12V. With what power does the lamp work if we connect it to a 6V battery? First,...
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1answer
148 views

Internal resistance and a resistor as a potential divider

Based on the fact that batteries have some kind of internal resistance, if I had a circuit that consisted of a battery and a resistor of some kind would they act like a potential (voltage) divider? ...
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23 views

How do I connect this 2V Diode to my circuit to fullfill the given requirements? [on hold]

So I am struggling a bit with an excercise. "Your task is to make a red diode light up by connecting it to a voltage source of 12V. The current through the diode should be 10mA, and then voltage ...
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How to go about solving this question? [closed]

This question is from first order circuit and under the heading of source free RL circuit (https://i.stack.imgur.com/SY1L6.jpg)
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1answer
455 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 ...
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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
316 views

Parallel combination of resistance [duplicate]

Why does the Equivalent resistance decrease when we connect resistors in parallel? I know current divides and potential difference is constant but my question is that if Equivalent resistance have ...
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15 views

Noise Fundamentals - Johnson Noise

How can be Johnson Noise measured with the help of single electronic instrument (experimentally)?
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35 views

Can somebody help out with this ridiculous circuit? [duplicate]

All the resistors are in ohms. I need to work out the current and power.
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2answers
238 views

How can I redraw this circuit where I can apply Kirchoff's Voltage and Current Law to get correct Voltage at V?

I thought I can draw the -5 V as a source but it did not turn out to be right, unfortunately.
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4answers
4k views

Why should a voltmeter have a higher resistance than of any circuit element across which the voltmeter is connected?

According to my textbook, it is said that, for an ammeter: It is essential that the resistance $R_A$ of the ammeter be very much smaller than other resistances in the circuit. Otherwise, the very ...
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1answer
118 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
49 views

Finding equivalent resistance of a complex circuit [closed]

I have a problem which asks for finding equivalent resistance of a circuit which cannot be simplified to a simpler circuit by mere observation. I tried to solve it by simplifying series resistance ...
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1answer
369 views

Material thickness, thermal conductivity and electrical resistivity

I have a plastic housing (for a printed circuit board- PCB) in the shape of a box (a *b *c) with L (thickness). Its material properties are: *thermal conductivity: $k_h~[...
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5answers
2k views

Why current in series circuit is the same?

I have read in the internet that the charges do not have any other path to go and they must go through the same in a series circuit,hence the current is same. It was quite convincing but what ...
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2answers
50 views

Why the potential across the voltmeter is not affected by changing metals? How can we prove it?

A voltmeter has both its leads made of metal Cu. When connected across a battery, it measures a voltage V. One of its leads is replaced by metal Au. But the potential across the voltmeter is not ...
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4answers
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Current and voltage [duplicate]

I am current studying A level physics. I know that current is the same in all parts of a series circuit, however I cannot understand why. If adding resistance to the circuit causes the kinetic energy ...
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5answers
2k views

Why is Kirchhoff's voltage law true in a DC circuit?

If we consider a single electron going around a closed loop, with a battery giving an EMF of $6\ \mathrm V$, why does the electron have to lose the energy in the loop? If the circuit had zero ...
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1answer
22 views

Resonance frequency and impedance of a piezoelectric element

I am reading about piezoelectric elements, and I have some questions in that regard. I have come across a graph showing the impedance as a function of frequency. Some spikes occurs on the graph at ...
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1answer
44 views

Why is the information of a time delay missing in formulae of voltage drop across elements when we emulate DC with an AC voltage supply?

In an AC circuit, the reactance of capacitive and inductive elements are determined by the frequency of the AC signal. When we try to emulate DC analysis by putting $\omega$ = 0 , the capacitive ...
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1answer
255 views

Why can one assume in “infinite grid of resistors” that in the center there are diagonal nodes that have $-1$ and $+1$ currents?

Why can one assume in "infinite grid of resistors" that in the center there are diagonal nodes that have $-1$ and $+1$ currents? As in the matrix $P$ in the following picture:
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2answers
3k views

Why high voltage transmission lines?

This is a question which I seem to have tackled multiple times, solved each time after reading a dodgy internet explanation, then partially forgotten about and retackled half a year later. It is time ...
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2answers
1k views

What is the value of EMF during a short circuit?

During a short-circuit, 'theoretically' current becomes infinite. But what about the emf? My attempt: Since the potential difference is zero, I guess the emf should also be zero. But again since p.d. ...
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1answer
2k views

How does an increase in potential difference increase the resistance of a non-Ohmic conductor?

I am a little confused with the reasoning of why an increase in potential difference (P.D.) increases the resistance of a non-Ohmic conductor, namely a filament lamp. From what I've seen this is the ...
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2answers
129 views

Surface charge on a resistive wire in DC circuit

I want to understand how does the energy transfered from battery to the resistor in a simple dc circuit . I read that it is due to the surface charge the battery creates on the wire. So why this ...
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2answers
49 views

A small size conductor causes a greater current in a circuit?

I have a question - let’s say I have a very small 2 wire cable connected to a load that draws a large amount of current, I’ve been told ( I have yet to do my own testing) that the smaller cable will ...
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3answers
478 views

Resistance and resistivity: which one is the intrinsic and which is the geometric property? Why?

The electrical resistance $R$ and electrical resistivity $\rho$ of a metal wire are related by $$\rho=\frac{RA}{l}$$ where $l$ is the length and $A$ is the cross-sectional area of the wire. One could ...
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1answer
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Relation between voltage and EMF of a battery [closed]

In the image :- R is resistance in the circuit r is the internal resistance of the battery E is the EMF of the battery V is the voltage across the resistor R Arrows show the direction of current. ...
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2answers
72 views

Why strong electric field leads to non-Ohmic behavior?

Homogenous conductors like silver or semiconductors like pure germanium or germanium containing impurities obey ohm's law within some range of electric field values. but if the field becomes too ...
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1answer
56 views

Can we add the resistivity due to different scattering mechanisms?

Suppose there's a metal in which electrons interact with themselves and with the phonons. The hamiltonian might look like this \begin{equation} H= \sum_{k}\epsilon_k c^\dagger_k c_k + \sum_{k}\...
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1answer
64 views

What exactly does Ohm's law say?

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, R ...
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3answers
150 views

Resultant force and constant velocity

Let's say for example, Jack is pushing on a box with force $F$, and John is pushing from the opposite side with force $F$ as well. We say that there is no resultant force, and the box remains stable ...
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2answers
58 views

A simple circuit problem / maximum power [closed]

Let us solve the first part for $R_{L}$. I used Thevenin to make its equivalent circuit. We get $R_{Th}$ or $R_{eq}=110/3=36.67$, so for maximum power transfer it must be equal to $R_{L}$. I can't ...
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1answer
60 views

What are the correct current directions? [closed]

i have a problem in my text book asking me to find the equivalent resistance of this circuit : so i used kirchhoff's first law and drew some abitritary current directions : the two 6 ohm resistors ...
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1answer
59 views

Why Does a Resistor's Resistance Vary?

Whenever we try to measure the resistance in a multimeter, the value is not the same for all measurements. Slight variations are observed over several measurements. But why this happens? And can this ...
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1answer
129 views

Open circuit in a constant electric field

In the figure, an external wire is "tapped" into a box inside which exists a constant electric field whose direction is from left to right. The wire does not touch the wall of the box, i.e., the wire ...
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1answer
136 views

Ohms law hold till what temp?

Is the Ohm's law verified to hold true at all temperatures? If not, then till what temperature does the Ohm's law hold? I think it is valid only till $0$ K and above. Am I right in my thinking?
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Solving resistance using symmetry

Recently I've been studying current electricity and I saw many books using symmetry to solve circuits. broadly categorised as left/right symmetry and up/down symmetry where we take current to be ...
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How relative positions of battery and galvanometer affect the sensitivity of a wheatstone bridge?

I know one of the factors that affect the sensitivity of the galvanometer is the relative magnitudes of the resistances in the four arms of the bridge. the bridge is most sensitive when all the four ...
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2answers
468 views

Why do we use a specific point to find the resistance of a non-ohmic conductor? Why not tangent?

I was wondering why can't the tangent be used to do this calculation? Can a randomly chosen point be used?
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163 views

The importance and the role of a switch in an electrical circuit

There is this simple test: Three identical bulbs are connected in the circuit illustrated in the figure. When switch $S$ is closed: a] The brightness of $A$ and $B$ remains the same, while $C$ goes ...
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3answers
461 views

Relationship Between Conductivity and Lossiness of a material

I read that a material is loss-less if the conductivity is zero. I have always learned that conductivity is a measure of how easily the material can conduct a current. Does this then mean that the ...
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It is possible that without resistance current flow a conductor [closed]

It is possible that without resistance current flow a conductor (answer with proof by)