Questions tagged [electrical-resistance]
The tag applies to electrical resistance and resistors. DO NOT USE THIS TAG for non-electrical resistance.
2,753
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What the hell is going on with electricity? [closed]
I am doing an engineering project and I need to understand basic stuff like Voltage, Electricity and Resistance. But I don't understand anything, electricity is much different than let's say special ...
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3
answers
70
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How would you find the equivalent resistance of these circuit diagrams given a wire with no resistor?
I understand how to combine resistors to find their equivalent resistance, but I am completely oblivious as to how to remove resistors that are shorted. For example, in the first image, there is a ...
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2
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38
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How is power dissipated proportion to current and current squared?
$P=IV$ and $P=I^2R$. Does this mean that $P$ is proportional to both $I$ and $I^2$? I don't understand this concept. And when should I use the various formulas for power? When another variable is ...
0
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1
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48
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What is the voltmeter measuring the PD of?
In the circuit diagram, the cell has an internal resistance, but when the switch is closed what does the voltmeter measure,
the pd of the cell, or the components in series?
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3
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55
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Why There's No Current Flowing in This Part of The Circuit?
One time, in my Physic Class my professor ask us, "How much current is flowing in this circuit?" and everyone answer $5$ Ampere (Because, it looks like the resistor is arrange in the series ...
1
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1
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How would having a non-ideal ammeter affect the resistance across this bulb?
A non-ideal ammeter is one that has resistance right. So that means that work will be done by the current flowing through the ammeter and there will be a potential difference across it. This will then ...
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0
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21
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Resistance needed to balance or nullify a specific current (Using Mesh Current Method) [closed]
I'm trying to solve a circuit analysis exercise in which I'm asked to find the value of $R_2$ (holding $R_1$ constant) in order for the electrical current $I_x$ to be cancelled/balanced.
In the ...
0
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2
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28
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What is the voltage across the capacitor and the charge it stores
Assume the switch has been on for a long time. Is it always the case that the voltage across the capacitor = the voltage of the battery? Even though they're in parallel.
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51
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Is This why current remains constant? [closed]
Great, i have yet another supposition.(i used a battery eliminator for variable voltage and not fixed as in a battery, in the first half of my supposition)
if i have a circuit consisting of 2 ...
0
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1
answer
24
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Mathematically solving for the energy loss in a resistor with ramping voltage over time [closed]
I am trying to calculate the total energy in a resistor where a constant voltage ramp is applied over time t. I am a little rusty on how to set it up.
We know energy is power multiplied with time or E ...
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0
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32
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Measure electrical fields in space with oscilloscope and wire [closed]
I have an oscilloscope with its standard probe. Combined they have 1MOhm resistance and 71pF capacitance.
I attach a 50cm wire floating in space to the probe and connect the ground clip of the probe ...
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2
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43
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Why is current constant in a series circuit?
This is more of a confirmation I require rather than a direct question, please do guide though, since I can be terribly wrong. (I do not have much knowledge of this.)
Current is defined as the ...
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1
answer
37
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Do small electrical field generators generate "different" electrical fields than long antennas - how to measure?
Modern electronic devices often generate electrical fields in the frequency range of 10-50kHz.
I want to distingush 2 categories:
Loaded onto mains (e.g. solar inverters) and then mains wiring emits ...
0
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1
answer
26
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Heating a Material with Negative temperature coefficient of resistance
TCR (Temperature Coefficient of Resistance): $R = R_0[1 + α(T - T₀)]$ Where: $R$ is the resistance at temperature $T$, $R_0$ is the resistance at a reference temperature $T_0$, $\alpha$ is the TCR of ...
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2
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40
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To calculate the resultant resistance of a circuit can you use all possible paths and assume they're parallel? [duplicate]
To calculate the resultant resistance of a circuit can you use all possible paths and assume they're parallel?
Say I have a circuit like this:
And I want to determine the resistance between x and y.
...
0
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1
answer
41
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Relaxation time in conductors [closed]
according to a crude (classical) model of the drift velocity as given in my high school textbook, using an example of cylindrical conductor, we derived ohm's law as
$j=\sigma E$
where $\sigma $
is the ...
0
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2
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72
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Why there is no current flow through earth via neutral wire?
From this thread How the current actually flows in a circuit?, I know that between 2 points in a conducting wire, the potential difference isn't necessary to maintain the current between them (if we ...
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2
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57
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Capacitor discharging connected to power supply AND resistor together
Lets say I have 2 capacitors P and Q connected to a 9V supply. Across P there's a resistor connected in parallel with the switch open (off position). When I turn on the battery they both fully charge. ...
2
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3
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149
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How the current actually flows in a circuit?
I'm studying about electricity and i'm quite lost.
Given the circuit in the picture, I just want to know how the current flows through the points A, B, C, D.
The condition to have current between 2 ...
0
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2
answers
66
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Find shape of minimum resistance between two points given a fixed volume of conductor
I am given a homogenous volume $F$ of isotropic conductor with resistivity $\rho$. I need to allow current to flow from Point A to B which are a distance $L$ away from each other. I can shape the ...
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3
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150
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Does the circuit need a wire?
I watched a YouTube video of Derek from Veritasium in which at 13:20, he claims that the lightbulb will turn on even if the circuit is broken, which astonishes me.
How can it be possible while when I ...
5
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85
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The resistor puzzle: with or without higher mathematics? [duplicate]
A fairly well-known puzzle asks for the resistance between two adjacent nodes of
an infinite square resistor grid, like the points A and B in the drawing.
If the resistors are all $1\Omega$, the ...
1
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2
answers
28
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Voltage/current direction of AC on circuit diagram?
Consider the following simple circuit consisting of an AC generator with voltage $V$ and a resistance $R$. As a result, current $I$ flows. Below the corresponding time-voltage diagram of the generator....
7
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2
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When the energy in a conductor is not carried by the electrons, how resistances warm up?
The energy flux in a conductor paints the picture that the "collisions" of the electrons with atoms (Drude Model) are not the reason for an resistance warming up in the presence of an ...
0
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0
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The inequality relation between the e.m.f. of two cells and the equivalent e.m.f
Consider two cells of e.m.f. $ε_1$ and $ε_2$ with internal resistances $r_1$ and $r_2$ respectively set up parallel to each other in a circuit as shown in the figure:
Let the equivalent e.m.f. be $ε_{...
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1
answer
47
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Telegraphers' equations for lossy transmission line when $R$, $L$, $G$, and $C$ are frequency dependent
The telegraphers' equations are commonly written as
$$\frac{{\partial v(z,t)}}{{\partial z}} + R\space i(z,t) + L\frac{{\partial i(z,t)}}{{\partial t}} = 0$$
$$\frac{{\partial i(z,t)}}{{\partial z}} + ...
0
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1
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41
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Why should the heating coil of a heater have high resistance?
In my book, it is given:
The resistivity of an alloy is generally higher than that of its constituent metals. Alloys do not oxidise (burn) readily at high temperatures. For this reason, they are ...
1
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1
answer
149
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Does resistance of a rheostat affect current in the circuit?
This is the typical experimental setup to determine the unknown resistance of a given wire. As we move the sliding contact of the rheostat, we get different values of voltage and current. a plot of V ...
0
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1
answer
48
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Writing the most general form resistivity tensor
I am unsure as to write the resistivity tensor in the most general form in 3 dimensions. Using the following equation. Please can someone explain?
$$\vec{E}=\frac{1}{ne}(\vec{j}\times\vec{B})+\frac{m}{...
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1
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30
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Resistance in series also slows current down so why is resistance connected in parallel in galvanometer ammeter and not in series?
When we convert a galvanometer into an ammeter we connect the resistance in parallel, the only reason we connect a resistance in parallel with galvanometer is so less current passes and the flow of ...
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1
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35
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Derivative of formula for battery's output power is not right
There is something about output power of battery in circuits that bothering me.
I hope you help me.
So we know the formula for power in electrical circuits is (current x voltage) or:
$$
P=IV
$$
and ...
0
votes
2
answers
100
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How to compute the resistance of a nonuniform cylinder with varying resistivity?
The generally quoted formula foe resistance is
\begin{equation}
R = \rho \ell/A
\end{equation}
some special cases are easy to solve. For example the case where the current flowing along the z-axis and ...
0
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1
answer
126
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Applying Microscopic Form of Ohm's Law to Leaky Capacitor
When we write $j=\sigma E$ in a conductor, is $E$ here the net electric field produced by the electrons and the source that drives the current? For example, inside an electrolytic cell (let us assume ...
0
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1
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46
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Discharge of a capacitor with variable backvoltage?
I understand that the voltage of a capacitor as it discharges overtime is $$V(t)=V_0e^(-t/RC).$$
I've also heard people say things like "voltage is relative. The voltage to the ground or the ...
0
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1
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68
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Electricity: Ohm law vs Power in the Water analogy
I'm trying to understand electricity principles with the water analogy. I know this analogy is not perfect, but so far it has helped me the most.
To recap:
voltage (volt) is like water pressure
...
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0
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EMF generation by rotating rod without magnetic field [closed]
what is the EMF generated by a conducting rotating rod of mass $m$ and length $l$ in free space without magnetic field. the rod is roating with angular speed $w$? also find the current if the rod has ...
0
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0
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25
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Which effect leads to the same electrical current in a closed circuit consisting of different resistive materials?
Suppose you connect two wires with different resistances to form a single wire. When you apply a voltage, a current will flow. Do the electrons in the wire with smaller resistance move with a higher ...
0
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1
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40
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Understanding voltage conservation by capacitive coupling
At work we faced the following problem:
We are working with some high voltage batteries which are located inside a casing which isolates the batteries. This means you cannot get any significant ...
0
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1
answer
77
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I find two different answers using Kirchoff's rules on single loop [closed]
I found this question in a book asking for voltage $X$. I allowed them to use any method they want. I too after revision using kirchoff's loop rules am getting too different answers. Please help me to ...
0
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1
answer
66
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Why is the electric field the strongest inside the resistors?
My understanding is that current is constant throughout the circuit. So it means that in the areas with high resistivity or small cross-sectional area the drift speed on electrons is the highest. ...
0
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1
answer
70
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Why is potential difference across resistor different than potential difference across a wire?
As far as I understand, the electric potential is the amount of energy that a third party agent has to spend to move a positive charge from infinite separation to a point. Thus, the electric potential ...
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1
answer
83
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Why are resistances measured in mutually orthogonal directions in Van der Pauw method?
In Van der Pauw method, two resistances are measured in orthogonal directions to each other. These are used to calculate sheet resistance from the Van der Pauw equation. Why is it that resistances are ...
0
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1
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101
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What would be the reading of the ammeter and voltmeter? [closed]
I came across this question which asked about the reading of the ammeter and voltmeter. I tried to solve it and deduced that the centre and right resistors are in series while the left one is in ...
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2
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106
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What is resistivity? [closed]
What is actually resistivity?
I read that when the temperature increases the the resistance of the conductor increase. Length and area of a material doesn't change so it means that the resistivity of ...
-1
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1
answer
37
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Continuity Equation on a Non-Ideal System
I recently watched a video on the diffusion equation for neutrons in a fissile material, and at about 2:30 minutes into the video, the author points out that the right hand side of the continuity ...
0
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1
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42
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Calculating $\langle Q^2\rangle$ for circuit with Johnson-Niquist noise [closed]
I have a problem from statistical mechanics which puzzles me as I never had a course in statistical mechanics.
So we have a series of a resistor and conductance and we assume that $Q/C=IR$ giving rise ...
1
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1
answer
397
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Equivalent resistance for an infinite ladder with resistances in arithmetic progression
I tried writing equivalent resistance as a functional equation of x with x as the lower limit, but couldn't proceed further.
Is there a better way to approach the question?
$$\frac{(x+1)f(x+2)}{(x+1)+...
1
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1
answer
53
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How does current work in this instance? [closed]
If current has two ways to flow in a single circuit, let’s say one path has a resistor of 5 Ohms and the other has no resistors whatsoever, will current still flow in both of the conductors?
Can ...
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0
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24
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Why are the resistors considered to be connected in parallel in this case? [duplicate]
in the first part (i) i am not able to understand why these resistors are considered that they are parallel. is because of the joints?
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0
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34
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How can I simplify this electric circuit? [duplicate]
I am having trouble simplifying this electric circuit. Should I neglect R1 in the simplification or not?