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

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Capacitor charging and discharging

I have a conceptual question. The circuit is shown below. Let us assume that the capacitor shown in the figure is of 2.2 micro-farads having rated level of 5 volts and we decide to charge it up to 2 ...
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621 views

Physical explanation for capacitive circuit

In capacitive circuit, the voltage and current are out of phase. the current leads the voltage by 90 degrees. this can be explained by these two equations: $$V = V_{\max} \sin \omega t$$ $$I = ...
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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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689 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 ...
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646 views

Why can't a superconductor make a DC motor self sustaining?

Superconducting wire can host a low current magnetic field. I do not know if it supports a corresponding electrical field. Can a superconducting wire that sustains a current accelerate a DC motor? ...
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284 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 ...
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156 views

Braess's Paradox in Electrical Circuits

According to this and other similar papers, http://www.nature.com/nature/journal/v352/n6337/abs/352699a0.html, adding a current-carrying path can increase the voltage drop across a circuit. What is ...
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is it possible to flow current in open circuit?

First , i don't know much about chemistry and physics. I'm just a graphic designer but i have this question in my mind. I'm sorry if this question is too basic and use 'generic' language. As i know ...
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274 views

Impedance Matching

When viewing fast pulses on an oscilloscope, why is impedance matching required? I'm not totally clear on why. I'm guessing it is because I don't want 'ringing' and because I want signal integrity.
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How electric currents can flow between 2 points at the same potential?

According to Ohm's law, if there is a potential difference, $V$, across a resistor then there is a current, $I$, flowing through it. Since we assume that points along the connecting wire are at the ...
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8k views

Confusion about P=VI and V=IR

If we look at $P=VI$, we see that if the current doubles then the potential difference is halved but this doesn't seem to make sense according to $V=IR$. If we look at that equation, since the ...
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2k views

Solving a rather unusual (diagonal) circuit

I have problems solving an electric circuit. I need to find the red drawn "I" (Current). However the way the electric circuit is drawn strikes me. I have very basic knowledge of physics and my skills ...
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372 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 ...
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143 views

What is the electric current $I_{12}$ and voltage $U_{12}$ in following electric circuit? [closed]

What is the electric current $I_{12}$ and voltage $U_{12}$ in following electric circuit? $I_{12}$ and $U_{12}$ are between points 1 and 2. . I have used this in constructing this electric circuit ...
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137 views

What is current of electric circuit which has only one component - a battery (or cell)? [closed]

What is current of electric circuit which has only one component a battery (or cell)? Explain why.
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269 views

Electromotive force

EMF is defined as: "The potential difference across the terminals of a battery or dry cell when it is giving no current to the circuit." So, if current starts to flow from the ...
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2k 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 ...
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2answers
413 views

Instantaneous current after battery unplugged in RL circuit?

I've been racking my brain over this, and I can't find any clues in my textbook as to how to approach it. I have the following circuit: My goal is to find R such that, right after the switch is ...
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39k views

Why do we use Root Mean Square (RMS) values when talking about AC voltage

What makes it a good idea to use RMS rather than peak values of current and voltage when we talk about or compute with AC signals.
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358 views

Compute closed line integral of electric field in circuit

I have a circuit where resistor is parallel to capacitor, which is charged with voltage U. How to compute line integral around closed loop to get the result of Kirchhof second law - ...
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290 views

Nodal Analysis of an electrical circuit

I have several doubts about solving circuits. Can any circuit be solved using Nodal Analysis? If some circuit can be solved using Nodal Analysis, can it be solved using Mesh Analysis too? Why do we ...
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427 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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1k views

Derivation of Ohm's Law

Is it possible to derive Ohm's law (perhaps in some appropriate limit) from Maxwell's Equations?
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7k 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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690 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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136 views

Microphones, Loudspeaker and their analogies to spring mass system

I have just started studying Microphones and Loudspeakers. I need a good text to refer which can explain their mechanical analogies with simplicity and basics too.
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210 views

Why is the anode (+) in a device that consumes power & (-) in one that provides power?

I was trying to figure out the flow of electrons in a battery connected to a circuit. Conventionally, current is from the (+) terminal to the (-) terminal of the battery. Realistically it flows the ...
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161 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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665 views

Can a battery charger be too powerful for a rechargeable battery?

I got the impression that a regular iPhone charger can charge the iPhone and the iPhone won't become too hot while charging, and the charging time is standard, but if using the 10W iPad charger to ...
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7k views

How does power consumption vary with the processor frequency in a typical computer?

I am looking for an estimate on the relationship between the rate of increase of power usage as the frequency of the processor is increased. Any references to findings on this would be helpful.
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143 views

Battery fully loaded, pull out the chord?

I recently bought a new phone (Samsung Galaxy 3) and when the battery is fully loaded, it says like "Battery fully loaded, pull out the chord". Is this a typo from Samsung, or would there ...
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146 views

What are the characteristics of a quadripole circuit element?

I'm reading Music, Physics and Engineering (H. Olson 1967), and contains models of musical instruments as electric circuits, i.e. uses the analogies between electrical circuits and mechanical ...
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326 views

Can inductance or resistance be negative or “infinite”?

Since the potential different or voltage drop is positive (am I allow to say voltage drop or potential difference in the presence of a changing current?), the current flows from right to left since ...
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410 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 ...
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770 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 ...
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213 views

How are quantum potential wells fabricated?

Potential wells, such as infinite and finite potential well, have been the standard examples in quantum mechanics textbooks for tens of years. They started being only theoretical toy models but as ...
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835 views

What are the effects of cosmic rays on consumer electronics?

When electronics/computer companies design a new chip, processor/ memory card/ or a solar cell, do they study the effect of cosmic rays on such electronically sensitive materials? If not, why not?
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251 views

Algorithmic approach for applying Kirchhoff's Rules to circuit analysis

Working with Kirchhoff's rules, I am attempting to device an algorithmic approach to finding the unknowns of the problems, I am of a Computer Science background and I am finding it difficult to ...
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96 views

what exactly do electric waves transfer from one point of the wire to other..? [duplicate]

Possible Duplicate: how does electricity propagate in a conductor? so basically i was considering the speed of the charges inside wire defined by the drift velocity and speed of electric ...
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594 views

Imaginary voltage in simple RC circuit

As a homework assignment, we have to find $U_a(\omega)$, that is the voltage that drops over the right resistor in relation to the frequency $\omega$ of the input AC voltage $U_e$. For the two ...
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1k views

Parallel or series connection?

Are C1, C2 and C3 connected in parallel, or C2, C3 in parallel and C1 in series with C23? Btw it appeared as a question in the basic physics Albanian A-levels yesterday. You had to find the ...
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Franck-Hertz Experiment explanation

Can anyone explain to me how the Franck-Hertz experiment works? (in term of electric current and voltage changes) I am getting all confused. More specifically, why is an accelerating grid (or mesh ...
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3k views

short circuit an alkaline battery

i'm not doing anything related to physics, but i'm just curious : What really happen when i short circuit an alkaline battery ? some article in the net shown that fire/explosion can be happened when ...
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Distorted colors of Google StreetView photographs near electric power lines

This is a followup to my question: Cyclist's electrical tingling under power lines Some users presented a convincing picture that the electric shocks under power lines are primarily from the ...
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177 views

Could a variable capacitor divider replace a Variac?

Hmmm... You can definitely drop down the voltage, and ideal capacitors don't dissipate any power. So it seems, at first glance, that you could use a capacitor divider as a lossless voltage step-down ...
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Two 60W-lightbulbs are connected on 220 V AC-voltage - how much electric power is spent by each lightbulb? [closed]

Two 60W-lightbulbs are connected on 220 V AC-voltage - how much electric power is spent by each lightbulb? There are two scenarios: In one, these two lighbulbs are connected serially, and in the ...
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1answer
267 views

Power dissipated in resistor

Suppose one has a circuit consisting of an inductor $L$ and resistor $R$ in series where $L$ and $R$ are known, passes an alternating voltage of frequency $\omega$ through it and that one wishes to ...
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287 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 ...
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How are the CPU power and temperature caculated/estimated?

From Wikipedia The power consumed by a CPU, is approximately proportional to CPU frequency, and to the square of the CPU voltage: $$ P = C V^2 f $$ (where C is capacitance, f is ...
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Cyclist's electrical tingling under power lines

It's been happening to me for years. I finally decided to ask users who are better with "practical physics" when I was told that my experience – that I am going to describe momentarily – prove that I ...