# 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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### I know that when it is closed the voltage should equal 1.4 , however Can you help me understand why the voltage would be equal to 4.2 when it is open! [closed]

I know that when it is closed the voltage should equal 1.4 , however Can you help me understand why the voltage would be equal to 4.2 when it is open
69 views

### Why does the current increase in this circuit?

I have understood the later parts of the model answer, but why does the current increase? I know that the brightness of a lamp is determined by its power which is given by $P=IV$. Since the current ...
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### Resistances and Capacitor Role in Smart Energy Meter System? [closed]

i have a question about the Resistances and Capacitor only, i just want to know what role they do here ?, what it does in the circuit ? if someone can explain it to me, i tried my best to understand ...
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### What is the area of a resistor?

I get confused every time in series and parallel questions. When two resistors are connected in series the area of combined resistors remains constant, and length gets doubled, while in parallel ...
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### Energy relationship of capacitor and inductor in $RLC$ circuit

Suppose I have an $RLC$ circuit , consisting of a capacitor of capacity $C$, an inductor $L$ with non-zero internal resistance $r > 1$ ohm and a resistance $R$. The following Claim: When the ...
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### Zero Shunt Resistance in Ammeter

To reduce the resistance of ammeter, we attach a shunt resistance in parallel to the galvanometer. Also, this allows galvanometer to measure larger currents even though it has less value of the full ...
44 views

### Laplace's Equation and maximizing electrical work

Both Karapetoff's The Electrical Circuit (pg 27) and this paper claim that in a conductor of irregular shape, if the voltage at both ends is taken constant the paths electric currents inside take will ...
1 vote
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### Process to find power dissipation across resistor for source-free RLC circuits for first cycle? [closed]

Q: A $0.01$ µF capacitor, a $0.1 H$ inductor whose resistance is $1000 Ω$, and a switch are connected in a series circuit. The capacitor is initially charged to a potential difference of $400 V$. The ...
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### Why the resistance in superconductors is zero? [duplicate]

Why the resistance in superconductors is zero? I know the BCS cooper pair formation but why in principle it behaves like that?
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I am very new to electronics and am a physics student working on an assignment. I have a very simple circuit set up in my bedroom: A power source of DC +0.7A and +5.0V with a single resistor of 100 ...
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### RC discharging equation/natural response

Why do we make this particular assumption when trying to derive the capacitor discharging equation/rc natural response? If we don't and solve the equation just by assuming Ir=Ic, then the equation ...
72 views

### Behaviour of current in Pure capacitive circuit with DC voltage across

A circuit has just 1 capacitor and a DC Battery (V volts) and the wire has no resistance. At time $t=0$ the capacitor is completely uncharged. How current in this circuit changes with time? What i ...
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### Unable to Understand How Current Divides in Parallel Circuits

for some context: I was self-studying and got confused about this question. This is a past paper question from the CAIE O Levels Board and its reference code is shown in the image attached below. I ...
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1 vote
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### Why does the phase difference of the capacitor voltage change with AC frequency?

In the graph below, the left vertical axis of the graph is the magnitude of voltage, the green line indicating the input voltage, blue line indicating the capacitor/inductor voltage. The right ...
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### High resistivity silicon detector

How is the resistivity of the silicon detector is related with the depletion of the detector bulk? In a thesis I read that to achieve low full depletion voltage, a high resitivity silicon detector is ...
1 vote
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### Derivation and theory for $I = kV^n$ [closed]

I performed an experiment in college to study the nature of a filament of a lamp, determine $k$ and $n$ in the relation mentioned, and study the variation of wattage of a lamp. I assume ohm's law is ...
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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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### 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 ...
51 views

### 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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### 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 ...
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1 vote
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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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### 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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### 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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1 vote
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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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### 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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### 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 ...
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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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### 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. ...
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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 ...
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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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### 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. ...
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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 ...
70 views

### 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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1 vote
156 views

### 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 ...
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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 ...
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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....
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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 ...
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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 $ε_{... • 390 1 vote 1 answer 47 views ### Telegraphers' equations for lossy transmission line when$R$,$L$,$G$, and$C$are frequency dependent The telegraphers' equations are commonly written as $$\frac{{\partial v(z,t)}}{{\partial z}} + R\space i(z,t) + L\frac{{\partial i(z,t)}}{{\partial t}} = 0$$ $$\frac{{\partial i(z,t)}}{{\partial z}} + ... 0 votes 1 answer 44 views ### Why should the heating coil of a heater have high resistance? In my book, it is given: The resistivity of an alloy is generally higher than that of its constituent metals. Alloys do not oxidise (burn) readily at high temperatures. For this reason, they are ... • 1,040 1 vote 1 answer 156 views ### Does resistance of a rheostat affect current in the circuit? This is the typical experimental setup to determine the unknown resistance of a given wire. As we move the sliding contact of the rheostat, we get different values of voltage and current. a plot of V ... • 19 0 votes 1 answer 49 views ### Writing the most general form resistivity tensor I am unsure as to write the resistivity tensor in the most general form in 3 dimensions. Using the following equation. Please can someone explain?$$\vec{E}=\frac{1}{ne}(\vec{j}\times\vec{B})+\frac{m}{... • 13 0 votes 1 answer 31 views ### 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 ... 0 votes 1 answer 36 views ### 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 ... 1 vote 2 answers 109 views ### How to compute the resistance of a nonuniform cylinder with varying resistivity? The generally quoted formula foe resistance is $$R = \rho \ell/A$$ some special cases are easy to solve. For example the case where the current flowing along the z-axis and ... • 181 0 votes 1 answer 129 views ### 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 ...
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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 ...