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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1answer
28 views
Five resistors' combined resistance [on hold]
There are 5 resistors.
Can you help me to find total resistance?
Sorry for image quality.
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0answers
21 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 $...
0
votes
1answer
35 views
Why the resistivity of differnet materials is different? [on hold]
On what factors it depend?
I have been wondering why it does not depend on the density of a substance. If atoms would be closely held then the flowing charges would have to face more obstruction.
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2answers
35 views
Are these resistors in parallel or series? [on hold]
So I am trying to find power dissipated in R2 but I have 2 different answers for if the resistors are in series or parallel and both answers are part of the options in the multiple choice to choose ...
1
vote
0answers
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 ...
-1
votes
0answers
30 views
Resistance ladder network [closed]
I have tried different ways of combining the four resistors, but how do I know which one is the correct combination? Is the equivalent 20/20 in parallel? Or simply 4x10 in series?
-1
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2answers
62 views
RC circuit series and parallel [closed]
R and 2R are in parallel.
4R and 3R are in parallel.
I dont know where to go after calculating the the parallel Rs.
Do you become in series? If so, how?
It is right after the switch is closed. So ...
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0answers
35 views
How to calculate the equivalent resistance across A nad B in the given figure? [closed]
Show step by step with reasons on how to calculate the equivalent resistance across A and B.
0
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0answers
28 views
What am I doing wrong with this Wheatstone Bridge? [migrated]
Experienced experimentalists, be aware that this is probably going to sound like a stupid question:
I am having a LOT of trouble predicting the output of this Wheatstone bridge circuit.
I am trying ...
0
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0answers
29 views
Total resistance of a light bulb with two parallel tungsten threads [closed]
I'm currently studying for my exams, and am kind of stuck at this question. Please note that I am translating from Danish to English as well as I can, but there might be any mistakes. Feel free to ask ...
0
votes
2answers
81 views
General idea behind simplifying cube resistors
I don't know if "cube resistors" is the right way of putting it, but I am wondering if somebody could walk me through the general procedure for solving problems in which you are asked to find the ...
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0answers
13 views
Numerically calculating total electrical resistance of a half sphere of a know material with know resistivity and dimensions
Asssuming I have a hemispherical laser melted area on a silicon wafer. I know the height (h), and diameter (d) of this melted region. I also know the electrical resistivity of this molten area. ...
2
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1answer
55 views
Why Electrical conductivity tensor is symmetric? Or is it not always symmetric?
How to show that the electrical conductivity tensor is symmetric? (or it's not always symmetric?)
2
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4answers
94 views
Internal resistance and Instantaneous current?
Okay, this would probably seem a pretty basic doubt but I can't understand this thing. I know that when the current is not flowing in the battery the voltage across the terminals is the emf of the ...
0
votes
1answer
52 views
Determining current in a branch having no resistor
In context to the diagram below , it is quite easy to find the current flowing through section AD , which turns out to be 2A , however , I cannot determine the current in any other branches with ...
1
vote
2answers
90 views
Can current travel backwards? [closed]
This is not a homework problem. I posted this specific question as it would be easy for me to explain.
If a current flows through the wire it encounters a short circuit 1 and after travelling through ...
0
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0answers
29 views
Does the electrical conductivity of any conductor decrease extremely due to very high temperature?
I learned that the specific resistance of any conductor increases with increase of temperature. Can a conductor turn into a non conductor due to extreme heat?
2
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2answers
56 views
How does a shunt save an electrical device?
Suppose there is circuit having an ideal DC voltage source (a high one) and a device having resistance R , therefore the current flowing in the circuit is $\frac {V}{R}$.It has been told that this ...
9
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2answers
866 views
Relativistic resistance transformation
During a discussion with my professor, he asked me about relativistic resistance transformation. Firstly I started with the formula $R=\frac{\rho L}{s}$, where $\rho$ is electric resistivity. So if ...
1
vote
1answer
40 views
How do we calculate the equivalent resistance of an infinite ladder if all the resistances involved are not equal? [closed]
actually I know how do we calculate the equivalent resistance of an infinite ladder network if all the resistors have the same resistance. But this particular question has just puzzled me. Please help ...
0
votes
2answers
38 views
What is the field that moves charges in a resistor?
We say a potential difference moves charges in a resistor.. i want to understand it in terms of field. What charge distribution produces a field in the resistor?
True, the cell produces a field.. but ...
0
votes
1answer
24 views
How does the thickness of a sample affect the accuracy of four-point probe resistance measurements?
I have been reading up on my experimental techniques, and I found a description of four terminal sensing here. It makes the statement that for accurate measurement of resistance the thickness of the ...
0
votes
2answers
48 views
Impedance of an LCR circuit
So I am trying to understand how to find the impedance of the parallel LC component of this filter circuit. I am given that the transfer function $\mathbf{T}_C = \dfrac{\mathbf{V}_{out}}{\mathbf{V}_{...
0
votes
1answer
29 views
Overestimation Problem [duplicate]
I had asked this problem earlier but I was too vague in how I asked it so I'm making a new post to be more specific.
Problem: Say we have a series circuit with an ammeter, a cell with internal ...
0
votes
1answer
26 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 ...
1
vote
5answers
84 views
Why does the potential difference across a type of parallel circuit not act like a potential divider? [closed]
Image credit (Q3)
In this attached circuit, when $R_1=0\Omega$, I am failing to understand how the two cells affect the potential difference across the central resistor R3. I understand that ...
0
votes
3answers
70 views
Voltmeter reads zero with two same batteries connected in series [closed]
this is an a level physics question, can someone here please explain why voltmeter reads zero and how changing resistance of variable resistor effects voltmeter reading.
The main concept i want to ...
0
votes
5answers
84 views
If current through a resistor is zero, does the circuit break?
I'm really confused. I'm studying about how capacitors are charged, and I learnt that there's a resistor attached in series with the capacitor when it is being charged. When the capacitor is fully ...
1
vote
0answers
13 views
Photoresistor in Parallel [closed]
I am currently building a photoresistor from a kit that I bought a few months ago. I had a few questions when I was building this circuit:
What happens when you wire the photoresistor in parallel ...
0
votes
0answers
31 views
Question about current density
I was looking at past exam papers and found a question that I can't understand. It is basically about current flow but the diagram is really confusing me. The diagram is the following:
The question ...
0
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0answers
52 views
Proof of Ohm's Law [duplicate]
I was watching MIT OCW 802 and the lecturer mentioned that Ohm's law has a proof by quantum mechanics. Can someone please explain this.
40
votes
3answers
12k views
Will the volt, ampere, ohm or other electrical units change on May 20th, 2019? [duplicate]
When watching a video by Veritasium about the SI units redefinition (5:29), a claim that the volt and unit of resistance (presumably the ohm) will change by about 1 part in 10 million caught my ...
0
votes
1answer
47 views
Evaporating tungsten wire
Consider an incandescent bulb having a thin filament of tungsten that is heated to high temperature by
passing an electric current. The hot filament emits black-body radiation. The filament is
...
2
votes
1answer
53 views
What is the cause of resistance?
I searched for this question on the internet but didn't got a satisfactory explanation.
What I thought on the topic is that the cause of resistance is 'the effective nuclear charge'. The nucleus ...
0
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3answers
44 views
Current Divider rule
If you have two resistors $R_{A},R_{B}$ connected in parallel with a battery, you can find the current that flows through one resistor ex.$R_{A}$ using the current divider rule:
$$I_{A}=\frac{V_{T}}{...
0
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0answers
36 views
Estimating the effect of inductors in an RL circuit
I'm trying to understand how an inductor works in an RL circuit. When I use an air core inductor, my estimation is fairly accurate to the test circuit but as soon as I use an inductor with a core, the ...
1
vote
1answer
102 views
I got this formula but can anyone prove it [closed]
Yesterday while doing some questions, I came across a formula that if a wire with uniform resistance R is made into n sided regular polygon then the net resistance between any two corners with $x-1$ ...
4
votes
2answers
105 views
Why does electrical resistivity have units of $\Omega \cdot \mathrm{m}$ rather than $\Omega \cdot \mathrm{m}^3 ?$
Electrical resistivity has units of $\Omega \cdot \mathrm{m} .$ However, since resistivity can be described as the resistance of a unit cube, shouldn't the units therefore be $\Omega \cdot \mathrm{m}^...
1
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1answer
67 views
Does the voltage of the battery change if you use it? [closed]
If you use the battery to charge a capacitor does the voltage of the battery decrease or still the same? Does the voltage of a capacitor decrease if you use it to charge another capacitor?
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votes
3answers
115 views
How does resistance affect the voltage drop? [closed]
There is a series curcuit and there are 5 resistors in it which are the light bulbs. I know that current is directly proportional to the voltage and inversely proportional to the resistance. Can ...
0
votes
2answers
48 views
Parallel circuits at home
My textbook states that if you have a light bulb turned on and you connected a hair dryer with it in parallel, then the brightness of the light bulb will decrease.
The reason my textbook provided, ...
1
vote
4answers
92 views
Inductance in superconducting wires (and the math)
I'm very curious about inductors in general, and how similar they are to capacitors.
In the above picture the formula of current over time in an inductor with wire resistance $R$ is written.
I'm ...
0
votes
2answers
74 views
Why I can't find a value for the resistivity of plastic? [closed]
I'm working to a relation about resistence of various materials. I haven't found a table of resistivity wich includes Plastic. Is searching plastic too general? Does a table in which there is at least ...
0
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0answers
33 views
How is energy transferred to a resistor in an electric circuit?
I'd really appreciate some help understanding this.
I've always thought that in a circuit, some source of potential (such as a battery) accelerates the electrons in the circuit, and that collisions ...
0
votes
1answer
23 views
How is current affected by a charging capacitor in parallel to a resistor?
Imagine a circuit with a battery followed by a lightbulb and an uncharged capacitor in parallel. Next to it is an open switch. When I close the switch completing the circuit, does the brightness of ...
1
vote
2answers
60 views
Current in the inductor at $t=0$
$L_1 = 5H, L_2=0.2H, M=0.5H, R_0=10 Ω$, and $i_g=e^{-10t}-10 A$. I need to find $i_2$.
I've started with DE
$$i_2R_0+L_2(di_2/dt)+M(di_g/dt)=0$$
and solved it for $i_2$, so $$i_2=0.625e^{-10t}+Ce^{-...
1
vote
3answers
63 views
When high voltage leads to low current in power transmission system how its not applicable for household voltages?
When high voltage leads to low current in power transmission system using transformers,how increase in voltage in household circuits from 220 volts makes the current increase damaging the appliances,
...
2
votes
2answers
89 views
Parasitic capacitance in real resistors
Typically, I'd assume (A) is only a justifiable answer when the two metal end caps have essentially infinite area, or when the spacing between end caps is far smaller than their respective areas, in ...
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votes
2answers
56 views
Power in Series and Parallel circuits
My textbooks states that the brightness of a light bulb that is connected in a circuit is determined by its power. That is, a light bulb connected in series would be brighter if it has a higher ...
1
vote
2answers
49 views
What should be the independent variable in a resistance experiment?
I was asked a question by a student today and I have been pondering about it for a while now. In an experiment to measure resistance of a conductor, should we vary voltage across the conductor and ...
