The electric-circuits tag has no wiki summary.
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3answers
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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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1answer
673 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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1answer
75 views
Full wave rectification [duplicate]
In the construction of a full wave rectifier, why is there central tapping in the secondary winding of the power transformer? What's the pure reason behind it? If there was no central tapping, what ...
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1answer
187 views
What is the role of center-tapping in a full wave rectifier?
Note: I have already tried googling. Although similar questions have been asked on different forums, I couldn't find a detailed explanation, which I could really understand.
Circuit diagram ...
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2answers
103 views
Under what condition charges do not flow in closed circuit?
I wanted to ask under what conditions will charges not flow in a closed circuit. Or when is current through the circuit zero even when an EMF is applied?
Like in the case of potentiometer, we say that ...
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0answers
29 views
half wave rectification [closed]
A.C of frequency 50 Hz was passed through a diode. The electricity thus obtained was used
to glow an led. Is there any peculiarity in the light from the LED? (1)
(b) If the glowing LED is whirled ...
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5answers
567 views
Parallel circuits - Overall resistance decreases with additional resistor
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 ...
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2answers
410 views
Capacitor circuits with light bulb
Let's say we have a normal circuit with a light bulb, with wires and a battery.
When one places a capacitor in this circuit, how is the light bulb able to light up, even when the capacitor prevents ...
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0answers
50 views
What is the value of the equivalent resistance? [closed]
Can anyone tell me the value of the equivalent resistance for resistors R7, R8 and R9 in the following image?
Circuit -> { http://www.mediafire.com/view/?ktct310wyvezf2x# }
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2answers
126 views
Why the CFL light bulb flashes even if there is a power cut?
Today when there was a power cut I saw that the CFL light bulbs were flashing time to time at regular interval. I was amazed as there was no source of power to the CFL bulbs even they were flashing as ...
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1answer
106 views
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 ...
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3answers
1k views
How much energy was consumed when we turn on/off light?
My parents told me to turn off the light when I am not using it. But I remember my physics teacher told me that the action of turning on/off a light can cause huge energy. I am wondering how much is ...
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1answer
470 views
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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1answer
92 views
a metal bar on a pair of conducting rails that carries a current
This is a homework question, and I solved it already, but something bugs me. So the problem is stated as following:
A metal bar of mass M sits on a pair of long horizontal conducting rails separated ...
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1answer
74 views
Weird circuitry problem [closed]
I should note that I am asking these questions on behalf of a friend who claims to be too busy. Anyway here is a circuitry problem:
Why is C the correct answer?
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4answers
134 views
Why is there a potential difference?
The question then asks for the potential difference between $X$ and $Y$, which is claimed to be $3.6\text{ volts}%$.
Why would there be a potential difference in this case? If I connect a lightbulb ...
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1answer
107 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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3answers
164 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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2answers
568 views
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?
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1answer
242 views
AC Circuit Theory Maximum Power Transfer
I am currently hitting a barrier with regards to the basics of this question.
A 50HZ supply is connected to various given impedance's, calculate the maximum power transfer.
Maximum power transfer I ...
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2answers
203 views
Why does the current stay the same in a circuit?
I was informed that in a circuit, the current will stay the same, and this is why the lightbulbs will light up (because in order for the current to stay the same, the drift speed of the electrons need ...
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3answers
330 views
Is this really how a capacitor works? Why doesn't it behave like a resistor?
My book says a capacitor is two conducts being connected by an insulator. Now let's take a parallel plate capacitor to simplify the problem I have.
Suppose I got two parallel plate capacitor in ...
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2answers
247 views
Why and how does symmetry work in circuits?
Why symmetry work in circuits? In my book there is no mention explanation as such for symmetry arguments and circuits. But there are circuits that are very difficult to solve without symmetry. Also I ...
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2answers
234 views
Why are AC quantities represented by sine waves always?
Usually we use a sinusoidal wave form to represent a alternating quantity. Why not a cosinusoidal wave or a ramp wave form?
In sine wave forms we can indicate the maximum and minimum amplitude and ...
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6answers
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In an alternating current, do electrons flow from the source to the device?
If electrons in an alternating current periodically reverse their direction, do they really flow? Won't they always come back to the same position?
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1answer
86 views
Inductively coupled DC circuit
The circuit under consideration has two inductively coupled loops, one with a DC battery, inductor, and resistor in series. The other loop has two inductors, one inductively coupled to the first, the ...
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0answers
359 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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1answer
63 views
Why does the presence of a battery change whether a circuit is in parallel or series?
If I take a closed circuit with two capacitors and a voltage difference, the circuit is apparently in parallel, but if I introduce a battery, the circuit is in series. Why does the presence of the ...
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2answers
195 views
Flow of electrons in a circuit
When the electrons flow in a circuit, so are those the electrons from the battery or are those the electrons of conductor like copper wire, etc..which are flowing in the circuit?
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1answer
151 views
Positive test charge
Protons have positive charge on them. Protons aren't mobile. So how can a positive test charge move from the negative terminal of a cell to the positive terminal and gain electric potential energy? ...
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2answers
104 views
Are there general circuits that differentiate/integrate empirically?
Is it possible to construct simple circuits, that given a time-varying input, produce an output that represents the derivative or integral of the input with respect to time?
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2answers
294 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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3answers
217 views
What is the current through the lamp?
We have the following circuit:
A neon lamp and a inductor are connected in parallel to a battery of 1.5 $V$. The inductor has a 1000 loops, a length of $5.0 cm$, an area of $12cm^2$ and a ...
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0answers
19 views
How are current and voltage out of phase in capacitive circuit? [duplicate]
Possible Duplicate:
Physical explanation for capacitive circuit
We say that in capacitive circuit, the voltage and current are out of phase. Current is 90 (degrees) ahead of voltage. What ...
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1answer
175 views
Explanation of the Graetz circuit
My knowledge of circuits is pretty rudimentary and I've never really understood circuits, so I'm having trouble with the concept of Graetz circuits:
When you register the voltage on the resistor R ...
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Explanation of NMOS processes
So, gate (poly-si + $SiO_2$) and $p^{-}$ silicon operate as capacitator.
But how are voltages and charges are applied? In order for inversion to occur, there should be charges formed in poly-Si, ...
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7answers
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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 ...
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0answers
100 views
Physics understanding of MOSFET and CMOS [closed]
CAn anyone provide me some clear links or explanation regarding physics understanding of MOSFET and CMOS? I know CS logic understanding - but I want to know how MOSFET and CMOS are created, and how ...
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1answer
118 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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1answer
350 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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2answers
203 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
406 views
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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2answers
166 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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2answers
676 views
Electric field of not-grounded conducting plate with a given potential?
I have been trying to find an equation (or some solution) of how to calculate the electric field strength (in N/C) of a conducting rectangular (nearly flat) plate which has non-zero potential to it, ...
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3answers
281 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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2answers
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The “Nerd Sniping” problem. Generalizations?
This question is motivated by this xkcd comic strip
.
The problem is indeed interesting, and my first recollection upon reading this was a similar problem in the book Problems in General Physics by ...
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1answer
152 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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3answers
210 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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0answers
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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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2answers
127 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.
