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

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Resistors in parallel: How do I make this rigorous? [closed]

In my revision guide it says "when two resistors are in parallel, the current has two paths it can flow through so there is less opposition to the current. This is why the combined resistance is less ...
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2answers
192 views

Why is there no induced electric field in the experiment (Faraday's Law)

Below are three circuit diagrams for each of Faraday's experiments that allowed Faraday to come up with Faraday's Law. In Griffiths' Introduction to Electrodynamics Griffiths states (on page 302 of ...
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1answer
18 views

Need help understanding appliance ratings

I keep coming across things like "A filament lamp rated 12 V, 1.0 A", or "a heating element rated 230V, 500W". I think the first one is saying that a 12V potential difference across it will make a ...
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1answer
38 views

Difficulty understanding electricity concepts

In circuit diagrams what does it mean for energy to be used in going through a component? I usually see this when emf is being described: total energy supplied per coulomb by battery = total energy ...
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0answers
37 views

Is shaking a phone enough energy to charge a smartphone?

Is shaking a phone enough energy to charge a smartphone? For example I'd like to use some kind of power generator to charge smartphone's battery but I'm wondering if shaking (by hand, or motion when ...
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1answer
46 views

What happens here in this capacitor?

What happens when we earth the circuit as shown below, why should it matter? because potential at a point is relative? So if the earlier potential was $V_p$ at that point, it becomes $0$, so every ...
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1answer
47 views

Why an inductor parallel with a light bulb makes it flash as a key closes the circuit?

The title is a simplified form of my question. To be precise, I'm talking about the following circuit: The inductor has a resistanse equal to the resistor in the circuit. So, the question is that, ...
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2answers
52 views

What is the rigorous definition for current in a closed circuit?

I know that $I = \frac {dq} {dt}$, but I have trouble reconciling that derivative definition with my intuitive understanding of current. At an arbitrary point in wire, the current is obviously the ...
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2answers
51 views

Voltmeter in series with a component?

I always see voltmeters connected in parallel with a component, but what happens if you connect it in series? I think it's due to the high resistance of a voltmeter but I don't really see why this ...
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1answer
100 views

Circuit analysis (Kirchoff's laws) for multi terminal resistors

Consider a four terminal resistor as shown here There exists a matrix resistance equation of the form $V_i=R_{ij}I_j$ for some $4\times 4$ matrix $R$ for each such four terminal resistor. I want to ...
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1answer
341 views

What would be the resistance of a wire, if it is stretched to double length? [closed]

If there is a wire of resistance $R$ and we stretch it such that it becomes 2 times longer, then what should be the new resistance of the wire?
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3answers
6k views

Why the bulb glows brighter?

If the total current is divided into the branches in a parallel configuration and it is constant in series. How come the bulbs glow brighter when connected in parallel than when connected in series?
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75 views

Deriving ODE for voltage across capacitor-RC circuit [closed]

I need to derive an ODE for the voltage across the capacitor in a specific RC circuit. The circuit has 1 resistor, one input, one capacitor and a switch. So far I have $$\frac{dv}{dt} ...
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1answer
47 views

Typo in physics book (capacitors)

I'm currently working through an AP revision guide. The section on charging a capacitor outlines the following steps: When a capacitor is connected to a battery, a current flows in the circuit until ...
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1answer
32 views

How long can a cellphone battery(pictured) power a LED light that produces light equivalent to traditional 60W bulb(800 lumens)?

Assuming Energy Star rated LEDs which produces 100 lumens/watts. Battery rated as 9.88Wh. Power consumption by LED = 800 lumens/100lumens/watt = 8 Watts Does it mean that it will power circuit for ...
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1answer
63 views

Calculating half power frequency (frequency response)

I am having a doubt in calculating half power frequency for a given RLC AC circuit. I have attached images of two questions with their solutions. In the first question, the equation for ...
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1answer
34 views

Diodes in AC current

If in AC current, the direction of the current is always changing, then if one was to place a diode (for simplicities sake lets say an LED) in an AC current, would it flash to the frequency of the ...
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1answer
49 views

Cryptic remark in physics revision guide

I am currently revising for my AP physics and I couldn't understand one of the end-of-section summary notes. It says: "Remember that the direction of magnetic field is from North to South, and that ...
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1answer
129 views

Avoid dependent equations when applying Kirchoff's Laws

I tutor college students in Physics. In particular, we are currently working on solving circuits using Kirchoff's Laws. In a recent problem, I ended up with a system of linearly dependent equations ...
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2answers
1k views

An Ideal Transformer

In a transformer assumed to be transformer, power in the primary is equal to power in the secondary. So in a sense, the power in the secondary is 'fixed'. Output voltage in the secondary is also fixed ...
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1answer
39 views

Faraday's Law: Current loop and proton

A single circular loop of wire with radius R carries a large clockwise current I(loop)=I0, which constrains a proton of mass M and charge e to travel in a small circle of radius r at constant speed ...
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1answer
69 views

Question on an unbalanced Wheatstone bridge

Let, P/Q = R/S in the usual sense of a Wheatstone bridge where PQRS are resistances. Then we know that the potential between midpoints of PQ and RS are equal and there's no potential difference ...
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5answers
2k views

Is current in superconductors infinite? If they have 0 resistance then I (V/R) should be infinite? [duplicate]

I learned many years ago that according to Ohm's law, current is equal to voltage divided by resistance. Now if superconductors have zero resistance then the current should be infinite. Moreover the ...
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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 ...
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1answer
37 views

Why doesn't the electric potential constantly decrease in a circuit as the current moves from the positive to the negative terminal?

Why doesn't the electric potential constantly decrease in a circuit as the current moves from the positive to the negative terminal? Details and Assumptions: 1. The wires show no resistance.
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3answers
402 views

Why does current density have a direction and not current?

As I understand it the definitions are as follows: Current is a scalar $I$ with units of $\mathrm{[J/s]}$. It is defined as $I=\frac{\mathrm{d}Q}{\mathrm{d}t}$. Current density is a vector $\vec{J}$ ...
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38 views

What is the theoretical reasoning behind calculating emfs in series or parallel?

First off, I did some research on my own but the answers weren't satisfactory. The analogy of the water pump makes zero sense as I see no way how "Potential" is even comparable with "Dynamic ...
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3answers
605 views

Electrostatic notion of voltage as it applies to circuits

I have a question that's been bothering me about electric fields, voltage, and circuit analysis. Initially, I came to understand voltage as it was taught in the context of electrostatics - through ...
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1answer
314 views

What would happen to electronic circuits when traveling near the speed of light?

Imagine a space ship, loaded with all sorts of computer systems, traveling near the speed of light. Electricity itself is very fast, and can reach speeds close the speed of light. (up to 99% ...
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36 views

Fastest converging series of resistors

I am looking for a recursive circuit which grows very fast and has a finite resistance but an infinite number of resistors. I have found many ways to get a finite given resistance with an infinite ...
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1answer
35 views

How can I physically demonstrate potential difference in a circuit to a 14 year old?

Children of this age have a fair idea about current, resistance, and batteries. Potential difference is a thing that cannot be felt or physically visualized. A teenager asked me if he can touch ...
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0answers
32 views

Origin of chaos in Chua's circuit

I am doing a project on Chua's circuit, but I can't seem to find anything that explains where the chaotic nature of the system comes from. Does anyone know of articles that explain it well on an ...
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6answers
19k views

Power dissipated in series versus in parallel

Do two resistors in parallel dissipate more heat per unit time for an applied voltage when compared to two resistors in series?
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1answer
24 views

Circuit with inductor

How would I find the current through each resistor/inductor as a function of time? I am lost conceptually here. (I made these numbers up, so they may not be "pretty" if/when taking equivalent ...
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1answer
47 views

How can I rearrange an equation to find a gradient for a capacitor?

If I plot R on the x axis and T on the y axis to give a straight line graph, and I am given that $V$ = $V_0$ * e^(-t/RC) then how can I prove that the gradient of the graph is equivalent to $C$ * ln3, ...
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3answers
281 views

Finding current in the circuit

Hi anyone. I try to de-draw the circuit in the simpler to calculate i1 and i2. But can not. Anyone have any hint to do this question ? . Or just give me the specific name of the way of how to do ...
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2answers
78 views

Homework: electrical circuit with 2 voltage sources & 1 switch

I can't figure out how to handle this circuit. I am asked to calculate the total resistance and the current over each resistance (R1-R4) when the switch is open. However I'm not getting anywhere ...
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Wave velocity (R)LC circuits.

I'm attempting to simulate some fluid like mechanics using circuits. Specifically wave propagation. I am attempting to measure the wave propagation velocity using an oscilloscope on the circuit below, ...
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29 views

How do I find the electron confinement energies in a spherical quantum dot?

So if I've got a spherical quantum dot, we'll say it has a 10nm diameter for simplicity. This dot is a semiconductor and it has an electron with an effective mass altered by a factor of 0.2. How do I ...
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19 views

How does one measure the power factor?

How does one measure the power factor? $$\text{power factor}\equiv\frac{\text{power}}{|V||I|}=\frac{R}{\sqrt{R^2+(1/\omega^2C^2)}}$$ for an RC circuit driven with $V(t)=V_0\cos{(\omega t)}$.
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1answer
67 views

Shouldn't the currents be time-continuous here?

My intuition is that the current upon an inductor (say, a solenoid) will always be time-continuous, without "sudden changes". But below is a case that seemingly contradicts this point of view. There ...
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3answers
65 views

How does the voltage across an inductor and a capacitor vary in series LCR circuit about resonance?

I am aware that at resonance, the voltage across the inductor and the capacitor are equal in magnitude and opposite in phase. However, I want to know how the voltage across $L$ and $C$ vary if I vary ...
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1answer
39 views

self inductance basic example: meaning of current flow AFTER opening circuit

while studying self-inductiance, I got into a tricky point... Consider this video: https://www.youtube.com/watch?v=0IVJaXO_0XA (minute 13.00). At this moment, opening of the R-L circuit is ...
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2answers
679 views

Do the copper connectors we used in measuring the resistance of a wire contribute to the said measurement?

We measured the resistance of a wire by setting the multimeter to ohmmeter mode and connected the ends of the ohmmeter to the ends of the wire; and we also calculated the theoretical value using a ...
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2answers
40 views

Simple Circuits [closed]

I have a small and easy dilemma, judging by how sophisticated the website is, and need a simple answer for it So $P=E/t$. And $P=I*V$. Therefore $E/t=I*V$. I just need an explanation on how this is ...
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1answer
71 views

Wheatstone bridge intuition - and the potential divider

I am having trouble understanding the working of a Wheatstone bridge. I am looking for an intuitive understanding of the process. Basically, I would like to have the following questions answered: ...
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2answers
79 views

Which lamp is brighter, the one through which electrons flow or current

I was thinking about problem that i don't really know the answer to. A circuit is set up with one battery and two identical lamps in series. Like so I know that electrons flow in the opposite ...
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0answers
16 views

Induced-EMF in a parallel circuit, vs a series circuit?

I wanted to know the difference between the induced-EMF in a series circuit layout, vs a parallel circuit layout. In a series the current would stay the same,however, the induced-EMF would increase? ...
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4answers
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Finding equivalent resistance in complex circuit

In my previous Phys.SE question, situated here, I asked about finding the equivalent resistance of the following circuit : I got some very good answers and some tips. Now what if the same circuit is ...