# 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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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?
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 ...
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 ...
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 ...
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 ...
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?
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 ...
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 ...
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 ...
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 ...
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.
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 ...
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. ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 $1/I= r/E + R/E$ ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...