Questions tagged [electrical-resistance]

The tag applies to electrical resistance and resistors. DO NOT USE THIS TAG for non-electrical resistance.

Filter by
Sorted by
Tagged with
5
votes
1answer
37 views

Why is contact resistance proportional to $\frac{1}{\sqrt{F}}$ not $\frac{1}{F}$?

See pages 13-15 in "Electrical Contacts: Principles and Applications" for reference. Imagine the following system: Two flat, but rough, surfaces of the same finite area $A$ being brought together. ...
0
votes
1answer
7 views

Resistance and temperature mathematical relationship of a thermistor

When I did an experiment measuring the Resistance of a thermistor as I increase or decrease the temperature, when I plot the resistance (y - axis) against temperature (x-axis), I get an exponential ...
1
vote
2answers
28 views

Voltage Change Across a Resistor/Circuit

Say you have a 9 volt battery, and you connect the two ends of the battery with a wire to form a circuit with no resistor. If you measure the potential difference between the two ends of the battery, ...
0
votes
1answer
55 views

What if I keep holding a household battery?

I have a question in my mind. What if I keep holding a Duracell(1.5V Battery) touching both the terminals with my fingertips? Will the circuit be completed and the battery drain? Or will it have no ...
0
votes
0answers
22 views
1
vote
2answers
35 views

Confusion in usage of formulae for power dissipated in a circuit

When should we use $\frac {V^2}{R}$ and when to use $I^2R$. Because many times they ask about the power without giving details about series and parallel. I am really confused
1
vote
3answers
54 views

Does temperature coefficient of resistance depend on geometry?

By temperature coefficient of resistance of a material about a reference point $T_0$, I mean $${1\over R(T_0)} \left.{dR\over dT}\right|_{T_0}.$$ All the sources (that I’ve seen) that quote this ...
0
votes
2answers
40 views

What am I supposed to look for in the question “What is the total resistance between $X$ and $Y$?” [on hold]

I'm not really concerned with answering the question but more so what I'm trying to look for. The question is "Three resistors are connected as shown. What is the total resistance between $X$ and $...
0
votes
2answers
43 views

Resistance and electricity

strong text In the answer to this question, it stated that the current would remain unchanged and I was wondering why the current would remain the same for the portion of the wire even though the ...
0
votes
3answers
56 views

Conceptually understanding RL circuits

I'm struggling to conceptually understand the current-time profile of an RL circuit. Specifically, what causes the rate of change of current, $\frac{\partial i}{\partial t}$, to start off high when ...
0
votes
1answer
74 views

Some confusion regarding RLC circuits

I'm a mathematics student, and it has been years since I last did current/voltage/resistor related subjects in high school. However, for one problem that I've encountered, I actually need to calculate ...
0
votes
1answer
31 views

In a simple resistor circuit, does the current reach V/R instantaneously?

Essentially, if I were to plot current against time for a simple circuit with a DC cell and a resistor in it, would there be a non-flat profile from time $t = 0$. So, between $t = 0$ and $t = t_1$, ...
0
votes
1answer
25 views

Why temperature co efficient value differ in different approach in calculation?

Q. resistance value is 18 ohm at 20 degree and 20 ohm at 50 degree. Find temp co efficient. sol 1- R=Rref(1+a(T-Tref)) a=temp co efficient =>20=18(1+a(50-20)) => a=1/270 sol2 - let Ro is ...
0
votes
2answers
48 views

How does a capacitor charge if there is zero voltage across it?

From what I understand, a resistor causes a voltage drop. So it would seem that the end of the capacitor attached to the resistor would have the same voltage as the end attached to the battery. If ...
3
votes
3answers
73 views

What is the time derivative of resistance?

Is there a unit for $\frac{\Omega}{sec}$? I have tried looking it up, but I can’t find anything
0
votes
3answers
52 views

Is there more than one legitimate way to determine whether resistor are in series or parallel?

On various other threads I noticed, that "If all of the current leaving one resistor enters another resistor, the two resistors are in series." similarly, "If the current must travel down two or ...
1
vote
0answers
27 views

Very basic Circuit Question [closed]

My Question is how would find the current of the ammeter I tried to solve by making 4 ohm and 8 ohm, which I believe are parallel as one effective resistance, and making 6 and 12 ohms which I ...
2
votes
3answers
60 views

Is it possible to heat water to boiling point using lightning rods? [closed]

This is just a thought i had when i was in the shower. Is it possible to heat water to boiling point using resistors in a circuit that diverts electric current from lightning strikes to ground? Sure ...
0
votes
6answers
75 views

Potential difference and current

According to Ohm's law: $V=IR$. Therefore $V$ is directly proportional to $I$. Furthermore, $V=W/q$ and $q=IT$. Thus $V=W/IT$. Therefore $V$ is inversely proportional to $I$. How can $V$ be both ...
-1
votes
1answer
62 views

How to save time while solving some complex circuit networks?

I know that this platform deals with mainstream physics and the questions raised here must be suitable for a broader community and must not be a specific problem. The questions based on some complex ...
0
votes
0answers
8 views

How would you find the time taken for a steady current for a superconductor?

For part (c) I need to find the time taken for the solenoid to gain maximum magnetic field strength. However, since it uses superconducting wires, the total resistance is zero, so how would I be able ...
1
vote
0answers
24 views

Equivalent resistance of an unequal geometrically progressing arrangement

I am a high school student and while going through one of my papers, I encountered this problem which I couldn't seem to solve. $\textbf{Question:}$ Find the equivalent resistance between the two ...
0
votes
3answers
52 views

What happens to resistance if we double current intensity?

problem: what happens to resistance if we double current intensity ? my attempt: ohm's law tells us $R = { V \over I }$ so : $${R \over 2} = { V \over 2I }$$ so resistance should decrease to half ...
-1
votes
0answers
11 views

Thevenin’s Theorem (confused) [duplicate]

I’m not really asking for a proof here but I just feel like I’m getting something wrong with this theorem.On the diagram below...from what I read Vs=VAB. Note that Vs =« Thevenin’s Voltage » and Rs=« ...
0
votes
0answers
18 views

How current flows in an ideal wire when there is no potential difference? [duplicate]

Such as in this case: Even though potential difference between points A and B is zero, a current of 9A will flow between these two points. Why it is so? I understand potential difference must exist ...
2
votes
3answers
68 views

Do electric charges in an electric field move at a constant speed?

The electric field is given by: $$\vec{E} = \frac{1}{q}\vec{F}$$ Electric charges create an electric field which, in turn, creates a force that accelerates charges. The Ohm's law, however, tells us ...
2
votes
2answers
74 views

How could an ideal conductor with 0 resistance conduct electricity? [duplicate]

A very simple circuit consist of a resistor, a battery, and some conducting wires connecting the resistor to the battery(assuming resistance of the conducting wire is $0$). It is always assumed that ...
0
votes
0answers
23 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 ...
0
votes
0answers
29 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,...
0
votes
0answers
15 views

Noise Fundamentals - Johnson Noise

How can be Johnson Noise measured with the help of single electronic instrument (experimentally)?
0
votes
0answers
37 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.
0
votes
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 ...
1
vote
4answers
80 views

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 ...
0
votes
1answer
53 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 ...
5
votes
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 ...
0
votes
1answer
23 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 ...
0
votes
1answer
45 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 ...
1
vote
2answers
50 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 ...
2
votes
2answers
73 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 ...
1
vote
1answer
67 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 ...
0
votes
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 ...
0
votes
1answer
60 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 ...
0
votes
1answer
63 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 ...
3
votes
1answer
61 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}\...
0
votes
0answers
26 views

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 ...
0
votes
0answers
14 views

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 ...
1
vote
0answers
28 views

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)
1
vote
0answers
8 views

“Directional” conductivity in linear flux-potential laws?

Question: Has the notion of "directional conductivity" been defined and used in the study of heat flow and electric current flow? Context: The table below gives three laws that describe linear flux-...
0
votes
1answer
39 views

Maximum metallic resistivity: dependence of resistivity on temperature

The electrical resistivity of metals usually increases with temperature. For a metal like copper at room temperature it increases almost linearly with temperature. At melting point we see a jump in ...
3
votes
1answer
48 views

Current in RC circuit

Why is current drawn in an RC circuit (in a circuit powered by DC voltage supply) independent of the capacitor used? While the capacitor is charging current drawn from the battery only depends on ...