# Tagged Questions

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### heat energy and resistance of an elctric circuit

Very often it is said that "heat is developed" in a resistance when there is an electric current in it. But as far as I know heat is defined as a form of energy being transferred due to difference in ...
39 views

### How to calculate resistance of bunches of wires

I figure that the resistance of multiple wires would work just like adding in parallel, a bunch of wires that is. But couldn't any wire just be viewed as a bunch of wires, albeit small ones? I know ...
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### How does current flow in a irregularly shaped heterogeneous resistor?

The motivation for my question is understanding how electricity gets through your skin as opposed to running along it, and how the presence of things like water on the skin affect the relative ...
28 views

### Question regarding inverse relation of resistance with area of cross section

It is said that resistance is inversely proportional to area of cross section. But greater area will have greater electric flux, and greater electric flux will have greater magnetic flux, and greater ...
54 views

### Thevenin equivalent of a circuit

Ok so I can't post the image of my question and my attempt at it, so I would like to ask, if anyone knows the steps to simplifying a circuit with dependent current sources, independent voltage ...
54 views

### How does symmetry allow a rapid determination of the current between $A$ and $B$?

The following was originally given to me as a homework question at my physics 2 course: Consider the following circuit The difference of potentials between the point $V_{1}$and the ...
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### Would the empirical behavior of a simple circuit match my model of it?

I have a practical problem in E&M which has baffled me and and my electrician. The copper water pipes in my house are carrying a current of small potential (~1V) AC current. Here is my ...
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### Which quantity gives the resistance of a component?

In a current vs potential difference graph, we can obtain the value of the resistance of the component. There are books that say gradient-inverse is the resistance and also books that say the value of ...
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### Does rubber insulate lightning more effectively than air?

Last week, an Ars Technica writer was struck by lightning. He says that the 911 operators were concerned about whether or not he was wearing shoes at the time, but he didn't think it would make much ...
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### Equivalent RC circuit to a RRC circuit?

I'm in doubt about a situation that I've seen sometimes: imagine we have a resistor in parallel with a resistor and a capacitor in series. Since I don't know how to generate figures of circuits to ...
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### Calculate the electric current in the given circuit when (a) Key K is open [closed]

Calculate the electric current in the given circuit when (a) Key K is open. (b) Key K is closed. !]each resistors of 6 ohm 1
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### Resistance of a copper wire [closed]

Resistance of a copper wire is 20ohm. If the diameter of the wire is 5mm and length 1ohm. Find the resistivity of the copper.
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### Resistors in Parallel

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 ...
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### 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 ...
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### Is this series or parallel? [closed]

How do you find I? and please explain which resistors are in parallel and which are in series? ("M" and ">" are resistors) ...
431 views

### Capacitors and resistor in series and in parallel [closed]

In this circuit, are $R_1$ and $C_1$ in parallel and $C_2$ and $R_2$ in series? I have think that the currents that flows trought $R_1$ isn't the same that flows trought $C_1$ so, $R_1$ and $C_1$ ...
121 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 ...
175 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 ...
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### Carbon resistor [closed]

a carbon resistor is used as a thermometer on a water day when the temperature is 10 degree Celsius the resistance of the carbon resistor is 270 ohms what is the temperature on a spring day when the ...
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### how to find the diameter of this fuse? [closed]

A fuse blows if the current exceeds 1.0 A. It is made of material that melts at a current density of 620A/cm2. What is the diameter of the wire, assumed to have a circular profile, in the fuse?
1k 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 ...
1k 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
189 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 ?
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### 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?
368 views

### How to find the equivalent resistance for the following circuit? [closed]

How do you find the equivalent resistance for the above circuit, if current is entering via A and leaving via C? Can it be done by treating it like a wheatstone bridge?
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### Resistance of Light Dependent Resistor (LDR)

Is there a mathematical expression relating the resistance of Light Dependent Resistor (LDR) with light intensity?
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### 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 ...
390 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 ...
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### 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 ...
191 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 ...
819 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 ...
734 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 ...
193 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 ...
2k 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 ...
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### Resistor branding color. [closed]

If I have a resistor with 100 volts applied to it with a resistance of 100 $\Omega$, then the resistor would dissipate 100W. What is the color branding? My first thought, following the table was, 1 ...
106 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 ...
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### 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 ...
317 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 ...
304 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 ...
176 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 ...
1k 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 ...
172 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 ...
596 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 ...
1k 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 ...
1k views

### What defines the brightness of a bulb?

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 ...