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Questions tagged [electric-circuits]

An electronic system, with closed loop current flow, and relative electrical potentials present across electrical components.

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Electricfield and faraday's law [duplicate]

Consider RL circuit consisting of a battery , resistance , inductor , and switch .all components are in series . If we close the switch at time t =0 the current will build up until reaching a maximum ...
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3answers
81 views

Electrons and wires [duplicate]

The electrons that carry the electric energy are in wires or in the battery ? battery provides a potential difference but from where electrons flow to make for example a bulb light. If they flow from ...
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2answers
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From where electrons flow to make a bulb light?

Suppose we have the "basic" stuff like a battery 2 piece of wire and a bulb. Battery has a potential difference. But from where electrons flow to make the bulb light? from wire or from battery or from ...
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1answer
71 views

Partially Filled Capacitors

I know that, for partially filled capacitors, one treats the space between the capacitor plates as two or more capacitors either in series or parallel. However, I don't fully understand why the ...
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0answers
68 views

Is this solution in Conquering the Physics GRE incorrect? [closed]

In Conquering the Physics GRE 2nd edition, Exam 3 problem 20, the statement is as follows: A metal bar is pulled at constant velocity $v\mathbf{\hat{x}}$ along two metal rails a distance $d$ apart ...
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1answer
84 views

Question about circuit with two cells [closed]

Edited - could someone explain how you treat a circuit with two cells in respect to circuit laws and also whether the section in the middle is in parallel or in series. Second Edit: I’ve researched ...
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1answer
50 views

The flow of electric current

If positive charges have higher electric potential difference than negative charges then why the negative charges (electrons) are the one that are moving in a circuit? and to my knowledge the ...
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4answers
108 views

How to understand Kirchhoff's Voltage Law?

I'm having a hard time trying to understand why Kirchhoff's Voltage Law is true. I looked for an answer on the forum but I couldn't find a convincing one. So my question is : How to "physically" ...
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2answers
117 views

Now what will happen in this circuit?

Consider a circuit as shown in this figure below- Assuming switch S1 is closed such that current flows in loop ABCDE for a long time and steady state is reached. Now, my question is simple, suppose (...
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1answer
67 views

Why is a parallel RLC circuit usually driven by a current source?

Almost always when I see an example of a parallel RLC/LC circuit diagram online, the circuit is driven by a current source instead of a voltage source. On the other hand, the series RLC is always ...
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9answers
6k views

The water analogy seems to imply that power = current. Why is this incorrect?

Many people think of the water analogy to try to explain how electromagnetic energy is delivered to a device in a circuit. Using that analogy, in a DC circuit, one could imagine the power-consuming ...
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2answers
44 views

The electric field between two plates of a capacitor

Suppose you a have a parallel plate capacitor connected to a battery of voltage $V$, and charge is starting to accumulate on the side of the capacitor connected to the positive end of the battery. ...
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4answers
92 views

How is energy conserved in a theoretical circuit where you put a lightbulb and two rechargeable batteries like… (diagram included)

In the beginning the first battery is fully charged, and the second is fully discharged. As the circuit is connected the discharging battery recharges a dead second battery and light is emitted from ...
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2answers
53 views

Why is the integration constant in a purely inductive AC circuit assumed to be zero?

While studying about AC circuits, I came across the usual differential equation of an AC circuit (in which the voltage across the source is a sinusoidal function of time) containing an inductor only. ...
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2answers
141 views

Current in infinitely long wire? [closed]

Theoretically, suppose an infinite-length wire with completely no resistance (0Ω) connected to the terminals of a battery, and an electric lamp placed in the "center" of said wire. The question is: ...
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2answers
36 views

What possible advantage could there be in connecting several identical batteries in parallel? [duplicate]

In two-cell flash light,the batteries are usually connected in series. Why not connect them in parallel?
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2answers
35 views

How does a piece of wire know there is a voltage potential different?

Imagine water molecules inside a water pipe is moving due to difference in pressure, this pressure can be due to difference in gravitational potential or external force like somebody squeezing at one ...
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0answers
20 views

How to derive reflected waves in AC circuit?

I was reading the wikipedia page "Reflections of signals on conducting lines". In the section "Arbitrary impedance" they consider a circuit consisting of an alternating source $2V_i$ and two ...
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1answer
27 views

Is the magnetic field cancelled out in a transformer?

https://physics.stackexchange.com/a/153501/213243 In the 3rd paragraph it is said that the magnetic field from the primary windings is cancelled out by the induced current from the secondary windings....
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1answer
118 views

Does Kirchhoff's Law always hold?

There's a bit of furore from this question on Youtube involving Dr. Walter Lewin and another Youtuber. With Dr. Lewin claiming Kirchhoff's Law doesn't always hold when magnetic fields are involved, ...
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2answers
36 views

Voltage across parallel resistances

A resistor is connected to a battery of certain potential difference, it has now $V$ volt potential difference across its ends, after some time a resistor is connected in parallel with it. How does ...
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1answer
27 views

Defining potential of the ground

In electronics, it is customary to define the potential of ground (thinking the Earth as a large conductor) as zero. Is this consistent with the fact that the Earth has a net electric charge that is ...
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1answer
16 views

Why does a stepup transformer increases voltage but reduces current?

I know its a really basic question knowing the fact that you could just plug in the Voltage and Current into the proportionality formula. The thing is that I want a 'scientific/logical' explanation ...
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2answers
57 views

What is the voltage in electrical circuits?

I understand what the voltage is and I realize that the battery makes an electric field due to the accumulation of the charges in the anode and cathode this electric field causes electric potential ...
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3answers
66 views

Is there an intuitive reason the resistance that maximizes power dissipation in this simple circuit has a simple form?

Consider the following circuit: A textbook problem[2] asks to find the resistance $R$ such that the power dissipated in $R$ is maximized (assuming $R_1$ and $R_2$ are fixed). I found that $R$ should ...
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1answer
44 views

Assumptions Involved in Circuit Derivations

When deriving formulae for RC, RLC, LC circuits, etc., we typically assume that current is steady. Griffiths gave a good explanation of why this assumption is reasonable (he states essentially that ...
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2answers
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AC circuit with no neutral output

I was referred here from the electrical engineering stackexchange, because my question is too theoretical. Consider the following circuit: Where $\varphi$ represents the phase of the AC power and ...
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2answers
51 views

Shot noise and single photon detection

I am looking into the noise considerations of a single photon detector, specifically an avalanche detector. I am wondering if it makes sense to think about shot noise when considering a single photon. ...
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1answer
37 views

How a battery maintains the current in the circuit? [duplicate]

How a battery maintains the current in the citcuit? Iwant to know each and every step of this process mathematically and theoretically also.
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1answer
14 views

The value of the driving frequency at which the voltage across the capacitor becomes maximum in a series RLC ac fed circuit

The circuit diagram is as shown. As per the book voltage across the capacitor is maximum during resonance that is p=1/√(LC) But what I found out is a bit different . And it is. p=√((1/LC)-(R²/2L²)) ...
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1answer
76 views

Why is smaller hardware faster?

I have a question regarding to hardware signal. There is a rule says "smaller is faster". In the link it says that that In high-speed machines, signal propagation is a major cause of delay; ...
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8answers
3k views

Understanding voltage and power in the fluid analogy for DC circuits

I am trying to understand electric circuits (ie voltage, current, power, and resistance). For the most part, everything makes perfect sense, but for some reason I do not feel as if I understand the ...
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1answer
50 views

Magnetic field at points on the circuit

I know magnetic field lines due to a circuit always form closed loops. Therefore $\nabla \cdot \vec{B}=0$ everywhere (even at points on the circuit). However due to singularity, magnetic fields are ...
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1answer
39 views

Movement of electrons in a circuit

Electrons move from negative to a positive terminal, but their path seems unusual. They seem to be taking the longer path to get to the positive terminal, The electrons could have gotten closer to ...
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1answer
28 views

Why potenial drops across a resistor in an electric circuit?

Why potential drop across a resistor in circuit? I want to know what causes this drop at the atomic level.
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1answer
22 views

Why is the potential difference across a conductor is equal to the battery voltage when it is connected to it

Why is the potential differencel across the conductor is equal to the battery voltage?
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0answers
58 views

How to calculate the current generated by a thin film?

I have a thin film with known dimensions and conductivity. If I hook up wires and apply a bias, how can I calculate/estimate the current that I will get? Here is where I'm at: $$ \mathbf{J}=\sigma \...
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1answer
33 views

Confusion about calculating resistances & terminal voltage

I'm looking at an exercise where a battery is powering two parallel light bulbs. Given are the battery's EMF ($12.0 V$) and its terminal voltage in this particular circuit ($11.8 V$), as well as the ...
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1answer
35 views

Maxwell-Faraday Equation and change in magnetic flux

Is the change in flux being equal to negative emf an experimental law? The Wikipedia derivation of emf as a negative change in magnetic flux in time: https://en.wikipedia.org/wiki/Faraday%...
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5answers
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What's the reason behind the current remaining the same after passing by a resistance?

I've been wondering why does this really happen, I mean by intuition if electrons are driven by EMF (ignoring wire's resistance), $n$ coulombs would pass by a point per second, until they encounter ...
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2answers
50 views

Charge accumulation at a bi-metallic junction

When we join two straight cylindrical wires of two different metals say iron and copper together such that their circular faces are in contact. If we make a constant current say I through the wires ...
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3answers
281 views

Kirchhoff's Voltage Law in a General Electromagnetic Field

Recently, Prof. Walter Lewin and YouTuber ElectroBOOM started a discussion about KVL, after Dr. Lewin claimed that KVL did not hold in the presence of an magneto-dynamic field. I would argue that Dr. ...
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4answers
71 views

What is the difference between the voltage in the electrical circuit and electrostatics?

In electrostatics it depends on the distance from the charges, should it also be in the circuit? But in practice, the voltage depends on the resistance, for example on a resistor. And the distance ...
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1answer
29 views

How do you calculate voltage drop in a neutral wire?

I've seen people saying that in practical situations, the voltage between the neutral wire and the ground is not exactly zero, is it true? And if yes, how do you find the voltage drop between these ...
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1answer
22 views

How to explain these observations on the first load, with two loads in series?

Recently I purchased the Snap Circuits Jr. kit and was working through the different projects with my daughter. We decided to connect two loads in series circuit, powered by the battery source. The ...
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3answers
44 views

Why isn't there current in R2 when capacitor is not fully charged

If we consider the switch to be closed, why would there be no current in R2. My understanding is that, as the current flows it will split into two at the junction, thus having a current charging C and ...
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1answer
44 views

Tesla coil tuning to space model

How do I model space so I can tune my tesla coil to give the most RF output at a required resonant frequency? The coil runs at 1 MHz that in aerial terms is a very short aerial so I am effectively ...
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1answer
75 views

Fourier transform of power

In the notes I am reading they use the following. Let $U$ be the voltage (depends on time) and $I$ the current in a circuit with some resistor with resistance $R$. Then the power is given by: $$P(t)=...
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1answer
54 views

How do we know that in an electric circuit, when charge leaves the battery, the same amount of charge enters the other side?

Conservation laws take the most seemingly complex of problems and boils them down to a simple abstraction, but they are huge statements to stand on. I'm just having a really hard time convincing ...
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3answers
350 views

Does touching the Live wire makes it neutral?

If I have two 'hot' wires connected to a source and a load, and one of the wire is connected to the ground, this wire is called the 'Neutral'. But what happens if instead of using an additional wire ...