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
3
votes
1answer
270 views

Help Understanding Non-conservative Fields

While watching a video lecture, I became uncomfortable with the results, (around 35 mins). The professor draws an electric circuit with a 1V batter, and two resistors (1 and 9 ohms). He then ...
13
votes
3answers
91k views

Why does increasing the temperature of a thermistor decrease it's resistance?

Surely, upon an increase in temperature, the atoms within the thermistor would vibrate with more energy and therefore more vigorously, hence making the electrons flowing through the electric circuit ...
-2
votes
3answers
7k views

Resistors in Parallel [closed]

From my book: "A length of wire is cut into five equal pieces. The five pieces are then connected in parallel, with the resulting resistance being 2.00 Ω. What was the resistance of the ...
31
votes
6answers
20k views

How can Ohm's law be correct if superconductors have 0 resistivity?

Ohm's law states that the relationship between current ( I ) voltage ( V ) and resistance ( R ) is $$I = \frac{V}{R}$$ However superconductors cause the resistance of a material to go to zero, and ...
0
votes
1answer
309 views

Confused on Calculating Resistance Distance Matrix

I am trying to create a computer program to compute the equivalent resistance over any points on any rectangular set of resistors (all with a resistance of 1 ohm). It seems that the resistance ...
20
votes
2answers
4k views

Why do Fermi liquids have $T^2$ resistivity?

I have often read that metals that are Fermi liquids should have a resistivity that varies with temperature like $\rho(T) = \rho(0) + a T^2 $. I guess the $T^2$ part is the resistance due to electron-...
1
vote
1answer
3k views

Calculate Capacitance in Series AC Circuits?

I'm supposed to calculate the capacitance of an unknown capacitor in series, but I'm not sure exactly which equation to use. I know the voltage across the resistor (Vr), voltage across the capacitor (...
4
votes
3answers
39k views

How exactly does a resistance reduce current?

I've heard that resistors are used to decrease current to a particular appliance, such as in the regulator of a fan. However, I've also heard that the total current in a circuit is always the same- in ...
5
votes
6answers
31k views

Parallel circuits - Overall resistance decreases with additional resistor [closed]

Let's say that there is a parallel circuit with two identical resistors in parallel with each other. If a third resistor, identical to the other two, is added in parallel with the first two, the ...
42
votes
15answers
100k views

I don't understand what we really mean by voltage drop

This post is my best effort to seek assistance on a topic which is quite vague to me, so that I am struggling to formulate my questions. I hope that someone will be able to figure out what it is I'm ...
0
votes
1answer
12k views

Relationship between resistance and voltage drop

In a series or parallel circuit, if two bulbs have the same resistance, do they have the same voltage drops? The problem I am asking about is below. Do A, B, and C have the same voltage drops since ...
2
votes
2answers
33k views

Physical interpretation of y-intercept in a Current vs Voltage graph

So I collected current and voltage data from a simple circuit with a power source and a resistor, using a multimeter. I created a graph for this data using excel and got the y-intercept (which is ...
0
votes
1answer
1k views

Cable TV version of infinite ladder network [closed]

This is a problem in a college physics textbook, and its bugging me that I can't get it. The figure shows a circuit model for the transmission of an electrical signal, such as cable TV, to a large ...
1
vote
3answers
3k views

kirchhoff's law.Simple question [closed]

So far I calculated total resistance and it is 4.66 ohms and there is 12 volt voltage across them, what is the best way or HOW to calculate current for each resistor ?
3
votes
2answers
13k views

Ohmic and Non-Ohmic devices

Why do some conductors follow Ohm's law and some do not? Isn't there any universal law that can explain the flow of current?
11
votes
7answers
22k views

Why does the current stay the same in a circuit?

I was informed that in a circuit, the current will stay the same, and this is why the lightbulbs will light up (because in order for the current to stay the same, the drift speed of the electrons need ...
0
votes
1answer
2k views

Finding Current and Voltage through resistors given overall voltage and resistor values

Given a setup like: Is it possible to find current and voltage through each resistors given resistor values and overall voltage (battery voltage I suppose). I think $$I_0=I_A=\frac{\Delta V}{R_{...
1
vote
1answer
2k views

Resistance of Light Dependent Resistor (LDR)

Is there a mathematical expression relating the resistance of Light Dependent Resistor (LDR) with light intensity?
12
votes
1answer
3k views

Resistance between two points in an infinite metal sphere/cube

Let's imagine that we have a tridimensional metal object of infinite size, and decide to calculate the resistance between two arbitrary points. How would we go about doing this? I have thought of two ...
4
votes
1answer
9k views

Effective resistance of inductor

In a lab experiment, we connected a simple circuit: an AC voltage source, connected (in series) to a variable resistor and an inductor. We measured the current in the circuit, and the voltage that ...
1
vote
1answer
2k views

How do I solve the current of this resistor using Maxwell's Current Theorem?

I've been trying to solve this using the method the prof. taught us, and I happen to know the answer but I can't reach it no matter how many times I've tried. The circuit in question is below: I am ...
2
votes
3answers
559 views

Is equivalent resistance always lower if we add a resistor to a passive electronic circuit?

How to prove that equivalent resistance of any passive network is always lower if we add a resistor between arbitrary two nodes? Note that this is not necessarily a parallel circuit, 2 nodes that we ...
2
votes
1answer
989 views

Solving a circuit with Kirchoff/Ohms Law

Good evening, I haven't had physics since year 7 and now I need to use elementary things in university. Since I lack a lot of basics I am now trying my best to fill these holes. Currently I am stuck ...
2
votes
2answers
6k views

Basic questions about voltage drop in DC circuit

I understand all the concepts of what voltage is using all the analogies but some things related to the drop of voltage across a circuit confuses me. If I had a short circuit and attached a voltmeter ...
8
votes
5answers
35k views

Current in series resistors and voltage drop in parallel resistors

When we have resistors in series, the current through all the resistors is same and the voltage drop (or simply voltage) at each resistor is different. Question 1: It is fine that voltage drop (...
4
votes
2answers
13k views

Wheatstone bridge galvanometer error

We had to measure the resistance of $R_x$, we balanced the Wheatstone bridge and did calculations. My question is: we didn't include galvanometer error into calculations. Why is that? I read that it's ...
0
votes
1answer
3k views

What does a positive gradient on a graph of V plotted against I mean in terms of EMF and internal resistance?

According to the equation $V = E-Ir$, the gradient of a graph of $V$ against $I$ should be $-r$ (internal resistance) and the Y intercept should be the EMF. Am I right? In an experiment I used a ...
12
votes
5answers
6k views

Derivation of Ohm's Law

Is it possible to derive Ohm's law (perhaps in some appropriate limit) from Maxwell's Equations?
3
votes
3answers
34k views

Finding current using EMF & internal resistance

What exactly is the difference between internal resistance and resistance? This came up in the context of a homework problem I have been given: The circuit shown in the figure contains two ...
6
votes
4answers
7k views

Do resistor-based fan regulators save no power at all?

I have heard that the traditional resistor-based fan speed regulators are inefficient. In fact, I have noticed that such regulators tend to get hot when the fan is set to low speed. However, does that ...
9
votes
5answers
5k views

Why there is electromagnetic resistivity $\approx 377\Omega$ in vacuum?

I cant understand that. If there isn't a material that makes it hard to pass, why there is a resistivity $\approx 377\Omega$ in vacuum?
1
vote
3answers
37k views

Average power dissipated by a resistor on AC current

So let's say we have an AC current of 120 V at 60 Hz. Then i's waveform would be $$f(t) = 120 \sqrt{2} \cos(2 \pi 60 t)$$ Or rather the amplitude times $\sqrt{2}$ times $\cos(2 \pi \times\text{...
1
vote
3answers
278 views

Why is current not 0 in a regular resistor - battery circuit immediately after you closed a circuit?

In regular open circuits with either a capacitor or inductor element, (when capacitor is uncharged) with a battery, when a switch is closed to complete the circuit the current is said to be 0 because ...
2
votes
1answer
244 views

Is Joule heating only between charged particles?

The Wikipedia page for Joule heating explains "It is now known that Joule heating is caused by interactions between the moving particles that form the current (usually, but not always, electrons) and ...
1
vote
1answer
738 views

Non-conservative Electric Field

I was watching this video from Walter Lewin and while watching these two videos, I noticed there is a "contradiction" in what he is doing. All links direct you exactly to where he begins, so you don't ...
0
votes
2answers
1k views

Voltage and resistance in series connection

In a series connection with n elements it is true that (voltage): $$V = V_1 + V_2 + ... +V_n$$ and (resistance): $$R = R_1 + R_2 + ... +R_n$$ If I know one of these I can infer the other. But is ...
11
votes
5answers
23k views

If a superconductor has zero resistance, does it have infinite amperage?

If amps = volts / ohms, and ohms is 0, then what is x volts / 0 ohms?
10
votes
1answer
5k views

Temperature dependence of resistivity in metals

We know that in high temperature, resistivity in metals goes linearly with temperature. As temperature is lowered, resistivity goes first as $T^5$ due to "electron-phonon" interaction, and then goes ...
5
votes
2answers
407 views

Modeling stochastic process with frequency-dependent power spectrum

I'm trying to model of Johnson-Nyquist noise propagation in a nonlinear circuit. An ideal (linear) resistor can be modeled very nicely by the Fokker-Planck equation (equivalently, the drift-diffusion ...
0
votes
2answers
5k views

RC circuit theory and voltage in the capacitor vs Ohm's Law

Consider a simple series RC circuit at steady state (capacitor is full). I've been told that once the capacitor is full we can literally "cut" the circuit because no current can flow. That ...
2
votes
2answers
398 views

Fundamentality of voltage to current

From Ohm's Law : Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. I would like to know if ...
4
votes
3answers
46k views

Why connect cells in parallel?

Say there is a circuit with two $1.5\ V$ cells and a $100 \ \Omega$ resistor. If you connect two cells in series, then the total emf is $3\ V$. And the current will be $3/100 = 0.03\ A$ (Using $V = IR$...
1
vote
3answers
4k views

Why does the potential drop across a battery and resistor equal the emf of the battery?

In this diagram you can see the potential difference across the battery and resistor is the same as the pd created by the battery (the battery and resistor are representing a battery with internal ...
13
votes
3answers
14k views

Is it possible to mathematically derive the formula for resistance?

Resistance is given by $\rho L/A$, where $\rho$ is the material constant, $L$ is the length, and $A$ is the area. Is there any way that this can be derived mathematically, or is the only way ...
-1
votes
2answers
14k views

What defines the brightness of a bulb? [closed]

So I have a question. There are three identical bulbs, 2 of them are connected in parallel and the third is basically in series, on the same circuit. If the one of the lamps in parallel breaks, what ...
15
votes
6answers
27k views

Resistor circuit that isn't parallel or series

What's the equivalent resistance in this circuit (between points A and B)?
-1
votes
2answers
1k views

what is the proper way to connect two light bulbs in a circuit? in series or parallel?

What is the proper way to connect two light bulbs in a circuit? in series or in parallel and why? My thought is that it's better to hook them in parallel, since if we take into account Ohm's Law, the ...
6
votes
3answers
10k views

General integral to find resistance

My question is: is there a simple and truly general equation for the resistance between two electrical equipotential surfaces?. Obviously, if so, what is it, and if not, why? It would be very ...
10
votes
1answer
5k views

Why does electrical current start to flow?

What happens microscopically when an electrical current starts to flow? I'd like to understand microscopically what happens in detail when electrons start moving (quasi-classically). Electrons can ...
11
votes
3answers
1k 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?