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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10
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3answers
823 views

Is a superconductor really a super conductor?

It is known that a superconductor is a material with electrical resistance zero. My question is, it is exactly zero, a theoretical zero, or for practical realistic reasons it is effectively zero?
4
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5answers
911 views

How can current pass through (resistance less) connecting wires?

This is not a duplicate of : Will current pass without any resistance?. I read it but my question isn't answered there. I'm a physics tutor for high school students and this is my understanding of ...
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1answer
13k views

Equivalent resistance of unbalanced Wheatstone Bridge [duplicate]

Equivalent resistance of a balanced Wheatstone Bridge is pretty simple: if the corresponding ratios are equal the just cancel the wire connecting the centre of two wires. But what if they are not ...
0
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3answers
449 views

RLC circuit - calculating resonant frequency

If I take a series RLC circuit connected to a battery, the impedance is minimized when $\omega = \frac{1}{\sqrt{LC}}$. I also know that the series RLC circuit is analogous to a damped driven harmonic ...
6
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1answer
2k views

Graph of Electrical Resistivity of Air vs Air Pressure

I've search many place ( Google, forums etc ) but can't seem to find anything that explains the Relationship between: Electrical Resistivity of Air vs Air Pressure Constant Variable: Temperature ...
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2answers
82k views

Why is stainless steel a poor conductor of electricity?

I recently had a metal plate put in my shoulder and was wondering why stainless steel isn't a good conductor (At least I hope it isn't). Does the alloy just lack free electrons? Why is that?
4
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2answers
627 views

What exactly is resistance and Ohm?

Ohm is defined as "a resistance between two points of a conductor when a constant potential difference of 1.0 volt, applied to these points, produces in the conductor a current of 1.0 ampere, the ...
3
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2answers
2k views

Is there charge build up before a resistor?

I understand that Kirchhoff's current law says that the current, $I$, is constant throughout a resistor, i.e. there is no build up of charge in a resistor. All charge going in to the resistor is the ...
3
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2answers
2k views

Calculating the resistance of a 3D shape between two points

If I have an arbitrarily shaped object made of a uniform material of some specified resistivity, how would I go about calculating the resistance between two measurement points with known contact ...
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4answers
136 views

How does resistance *really* work? (DC, battery, LED, atoms, electrons)

Backstory: I’m a software engineer just getting into electronics and it seems that everything I’ve ever been told about electricity my whole life is a candy-coated lie. I can’t find consistent logical ...
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1answer
477 views

Impedance of the infinitely long circuit

Is there a way to find impedance of the infinite circuit like this? It will be much simpler if one has either parallel or series combination but here is both.
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3answers
3k views

If Resistivity = $\frac{RA}{L}$, why does it not depend on dimension?

The formula for resistivity is: $$\rho = \frac{RA}{L}$$ where $\rho$ is resistivity, $R$ is resistance, $A$ is cross-sectional area, and $L$ is the length of the conductor. We can see from the ...
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1answer
4k views

Dependent and Independent Variables in an Electrical Experiment [closed]

So, for my science fair I had to test the gauge of a copper wire vs electrical resistance. What I did was I set up a series circuit involving a 6v battery, a light bulb, a multimeter, and a voltmeter. ...
4
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2answers
5k views

What causes a resistor to heat up?

In the following video clip at 2:10, http://www.youtube.com/v/YslOUw5oueQ , Professor Walter Lewin talks about a misconception people have that the energy going through a wire to a resistor is in ...
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1answer
1k views

Why is 2-terminal sensing less accurate than 4-terminal sensing if the internal resistance of leads is known?

I have a pretty good understanding of 2-terminal vs. 4-terminal (kelvin) sensing measurements. I understand that in the 4-terminal measurement, current is supplied by 2 terminals that are separate ...
2
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4answers
137 views

In a simple battery + resistor circuit, what form of energy is lost from the electrons upon exiting the resistor?

I will give this question a little context. Firstly, as I understand it, as soon as I "close the switch" on a circuit, electric current pretty quickly establishes a steady state where, at any given ...
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2answers
813 views

Why isn't resistance proportional to distance squared

Here we have a wire. At both ends there is an equal and opposite field caused by a chemical reaction. So, if we decrease or increase the distance between the two points, the strength of the field ...
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1answer
98 views

Is zero input impedance good or possible when considering impedance matching? [closed]

For RF applications, we are usually considering of impedance matching to choose load impedance as the conjugate of the source input impedance for the maximum transferred power. But how about design ...
1
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2answers
54 views

Why do the following Network Transformations give different answers?

I did a Star to Delta Network Transformation and a Delta to Star Network Transformation on different parts of the original circuit as shown in the image below. It gave me two new circuits. On solving ...
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4answers
1k views

The sign of the current flowing in a circuit

I was doing the following problem: And I was asked to find Iy. I found Iy to be 2.64 using KCL. However, the right answer was negative 2.64. Is it negative only because there is a dependant ...
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1answer
600 views

Resistors in para and series circuit, finding volt [closed]

How anyone know how to do the question? I know how to reduce it to a window pane of 6/6/6/6 with a 3 in series but i have no idea how to do it. Well i did manage to reduce the right side of the ...
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3answers
539 views

Heating of an non-ohmic conductor

So I know that if you increase the voltage across a wire then the current will increase. But an increase in current leads to a increase in heat production though $P=I^2R$, but as the temperature ...
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0answers
87 views

How can current flow in an ideal wire if all of its points are at the same potential? [duplicate]

If I have an ideal wire and I connect a battery to it, then the potential drop is zero along the wire, right? So, all its points must be at the same potential. Well, that means charges ( which are ...
0
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1answer
31 views

When the external resistor increases in temperature, why is the calculated value for internal resistance higher?

Say we had a circuit with a cell (with internal resistance)and an external resistor of 10 ohms as shown: The 10 ohm resistor then increases in temperature, leading to an increase in resistance in ...
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1answer
2k views

How does the equation $1/I = r/E +R/E$ relate to $ y=mx+c$? [duplicate]

I have a graph of $1/$current against resistance, which is a straight line of positive gradient. I know that the gradient represents $1/V$ but I can't work out how the equation $1/I= r/E + R/E$ ...
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4answers
2k views

Why must identical lightbulbs in series have identical voltage drops?

When I connect two identical lightbulbs in series, how come they have equal brightness? Why can't one lightbulb have a larger voltage drop than the other? (i.e. the first lightbulb "uses up all the ...
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4answers
1k views

Ohmic Heating in Wires

please could someone tell me why Ohmic losses are always referred to as $I^2 R$ losses? Here is my problem. If the power coming from a power station is fixed then you can either deliver this power as ...
37
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5answers
22k views

If the Earth is a good conductor of electricity, why don't people get electrocuted every time they touch the Earth?

Since the Earth is a good conductor of electricity, is it safe to assume that any charge that flows down to the Earth must be redistributed into the Earth in and along all directions? Does this also ...
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6answers
5k views

Intuitively, Why is Power Proportional to $I^2R$

As the resistance of a circuit goes down, the power increases because the current increases, assuming constant voltage. Why is this? I feel like resistance and current are inversely proportional, so ...
20
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3answers
7k views

How is silver a better conductor than platinum?

Based on my understanding, platinum should be a better conductor than silver. Here's my reasoning and assumptions. An atom's ability to conduct is based on the amount of energy required to displace ...
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5answers
2k views

Does electron-electron scattering contribute to resistivity?

Electron-phonon and electron-defect scattering clearly contributes to resistance, but pure electron-electron scattering conserves the total momentum (and energy) of all the electrons. Then, how is it ...
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4answers
3k views

Physical meaning of Impedance

So I have been thinking about the way impedance is defined for electrical systems, and the way it is derived. Even after looking through some websites, I cannot seem to grasp something, which every ...
20
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3answers
9k views

Can a superconducting wire conduct unlimited current?

A superconducting wire has no electrical resistance and as such it does not heat up when current passes through it. Non-superconducting wires can be damaged by too much current, because they get too ...
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4answers
6k views

Symmetry in resistor circuits

Given 6 points that are connected with each other with a resistor of resistance $R$, find the resistance between any two points. (Answer: $R/3$) (All the conducting wires have the same resistance $...
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1answer
252 views

Why does the superposition principle for calculating equivalent resistance work for asymmetrical objects?

The method has been discussed in this question: Effective resistance across 2 adjacent vertices of a dodecahedron with each edge $r$ I used this method for an asymmetrical object to calculate its ...
7
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3answers
8k views

How to find points with same potential while solving an equivalent resistance problem?

Lately, I've been reading about techniques to reduce networks and find their equivalent resistance/capacitance. While doing this, I came across the cube resistance problem and many other problems (eg. ...
8
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4answers
3k views

Contradiction in Ohm's Law and relation $P=VI$

Ohm's law states that  electric current is directly proportional to voltage provided that physical conditions like temperature remain constant i.e. $$V = IR$$ On the other hand, $$\text{Power = ...
4
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4answers
852 views

How does resistance convert voltage to current? [closed]

This is a statement that I read mainly on books about electronics. Could someone explain why after the resistance current is what makes things work and not voltage? Example from the Art of ...
3
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1answer
1k views

Effective resistance across 2 adjacent vertices of a dodecahedron with each edge $r$

What will be the effective resistance across 2 adjacent vertices of a regular dodecahedron (12 faces) with each edge having resistance $r$? Here is the source for the problem, it's problem 20. on ...
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2answers
1k views

Olympiad physics 1996 problem [closed]

I don't understand the official solution of the first problem of the 1996 International Physics Olympiad. They give this circuit: Each black box is a resistor of resistance $1\Omega$. They then ...
2
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1answer
9k views

Relation between Terminal Voltage and EMF of a cell while the cell is being charged

I know the relation between the terminal voltage, V and emf of the cell, V' while charging given by V = V' + Ir where I = Current in the circuit and r = Internal Resistance of Cell Can anyone ...
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5answers
3k views

Reversed First Joule's Law : heating a resistor produce voltage?

I was discussing about the theory that claims that "every emitter also behaves like a receptor": Are emitters always receptors? I was brilliantly told that this theory would be false for fluorescent ...
13
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6answers
39k views

How to measure resistance of a piece of wire?

My son is doing a science experiment on how varying temperature and diameter of wire impacts the resistance. We are assuming we can accomplish this by using different gauge wires, a home thermometer, ...
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4answers
1k views

Why do superconductors conduct electricity without resistance?

Many authors have suggested that persistent currents in superconducting rings arise from the energy gap in the single-particle spectrum. Indeed, the argument has been put forward many times on this ...
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3answers
4k views

How does electricity 'decide' on it's pathway? [duplicate]

I'm struggling to understand the fundamental concepts of electricity, more specifically, the way in which it 'chooses' its optimal pathway. I appreciate electricity will always choose the path of ...
7
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3answers
17k views

If the current is increased, is there more charge flowing or is it moving quicker?

Problem Current is the amount of charge that is flowing through a component per unit of time. For a given voltage, Ohm's law tells us that if we increase the resistance, then the current must ...
6
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2answers
12k views

how calculate resistance between two points for arbitrary resistor grid?

I need to calculate resistance in an electrical grid. Grid is a graph. Edges of a graph are resistors. How calculate resistance between any two vertexes for arbitrary graph? I know Kirchoff law and ...
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2answers
3k views

Why resistivity of copper wire is not zero even at zero kelvin?

At zero kelvin, everything seems dead stop. There is no movement occurring at zero kelvin, even at atomic level. As there is no movement in atoms, there is no vibration of atoms about their mean ...
4
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1answer
702 views

Saving energy while charging capacitor

While charging a capacitor by a DC source, half energy is wasted as heat. Can't we save that energy? Here I am talking about $$(1/2)CV^2 $$ which is wasted while supplying $$CV^2$$
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2answers
4k views

How are band gap energy, dielectric constant (permittivity) and resistance related to each other?

The following three properties are related to current flow: Band gap energy Dielectric constant Resistance I would expect them all to have the same trend (i.e. higher band gap energy would cause ...