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

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711 views

How is the current flow perpendicular to the wire?

This answer gives a great explanation of how surface charge builds up to force the current to move perpendicular to the wire: http://physics.stackexchange.com/a/102936/41086 However, it fails to ...
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2answers
111 views

Capacitor/Inductor Resonance

I am struggling to understand the concept on resonance in electric circuits. I understand that a inductor builds up a charge on it, then the current flows to the capacitor, charging it. But then ...
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1answer
43 views

Even when the drift velocity of the electrons is very small, how is current in the circuit established immediately?

So I have this question in my textbook and Ive also got it in my test. Ive written a wrong answer. My friend wrote the drift velocities of each particle add up and he got full marks. Is it right? Can ...
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1answer
239 views

Are magnetic hysteresis losses relevant to alternating currents flowing in a wire?

Say we have an AC in a magnetically lossy material, like iron. Because of iron's relatively high permeability, skin effect will be more pronounced than it is in say, copper, so this iron wire isn't so ...
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1answer
29 views

Earthing, neutral and Earth's conductivity

Ok so this is gonna be a lot of mini-questions. What exactly is the neutral wire? How does earth conduct electricity for a live AC mains even though its just dirt and stones (it should be an ...
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1answer
76 views

What is capacitance, in general?

In circuit analysis software capacitance can be measured between any two nodes of a circuit or of a multiterminal device. In practical terms we take $C_{ij}$, the capacitance between $i$ and $j$ as ...
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1answer
42 views

What happens when an AC source is connected to a capacitor and a LED?

When a DC source is connected to a capacitor and a LED, and the voltage is removed when capacitor is charged, the capacitor supplies current to it for some time. What happens if this DC source is ...
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2answers
143 views

Why does a battery die more quickly when more resistors are added to the circuit?

I will be explaining what I think: A battery acts like a pump which provides energy to do work on negative charges to move them towards the negative terminal, and hence creating an electric field. ...
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1answer
22 views

holes in an electronic circuit [on hold]

Many times, by looking at electronics circuits I noticed that they have like small holes printed in yhem. The question I want to ask is, what s the purpose of these holes?
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4answers
80 views

Which makes for a better equivalent capacitor? In series or in parrallel? [on hold]

I understand how capacitors in series and in parallel work. However, I am wondering if it makes a difference, in terms of making a better capacitor that can store more charge, would you connect them ...
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1answer
35 views

Laser as an optical oscillator

How can Laser can be compared to a positive feedback amplifier? Does the two conditions for oscillator holds good for lasers too.
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3answers
79 views

Is power still consumed when we switch off the lights?

I was having heated discussion with one of my friends. We were discussing Earth Hour and its role in saving electricity, and creating awareness. He stated that even if you turn off the lights, the ...
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1answer
42 views

Resistor in series

We know that when a resistor is connected in series , the current flowing through that resistor will be constant.But how do we use a resistor to limit the current flowing through a circuit ,when ...
1
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1answer
55 views

Proof of Kirchoff's second law

There are 2 approaches I have stumbled to prove Kirchhoff's second law: Derive it from the conservation of energy. You can derive that from "integral of E*ds = 0". Can you show me a full or at ...
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2answers
26 views

Elementary derivation of $P = UI$ starting from the definition of voltage as work done per unit charge

Consider the following elementary derivation of the formula $P = VI$ for Joule heating of a resistor $R$ for the dissipated power $P$ where the voltage over the resistor is $V$ and the current $I$. ...
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0answers
52 views

Minus sign in analyzing RC with changing emf circuit?

I'm learning electromagnetism from Purcell's book. He say that if we have the following circuit: $$-\frac QC + RI = \mathcal E_0\cos\omega t~,\quad I = -\frac{\mathrm dQ}{\mathrm dt} $$ The ...
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1answer
126 views

Back EMF & Current, how can we make the current $I$ stable?

Lets assume we have a wire that has $10V$ across and $1$ $Amp$ flowing, now if this conductor is introduced to a changing magnetic field, $-EMF$ is induced, can we control our voltage to increase it ...
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1answer
38 views

Possible reasons of electrocution in a good earthed appliance during sudden power off [on hold]

I was working in a industry. When I was using a machine, I felt slight electrical shock at the exact moment when the power supply went off. The machine is properly earthed. In spite of that I got ...
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0answers
21 views

Equivalent Resistance in electrical circuit [closed]

4 resistances of value 1 ohm each forms a quadrilateral.Each diagonals of a quadrilateral also consists of 2 resistors of value 1 ohm each.What will be the value equivalent resistance of the circuit ...
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2answers
247 views

Calculation of RMS current in half wave rectifier

While calculating RMS current in half wave rectifier, why we will consider only half wave that means only we consider the limits 0 to pi. But here RMS current is for AC input..so why don't we consider ...
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0answers
16 views

What's the back EMF on a spherical conductor suddenly surrounded by a negatively charged shell?

Suppose one has a spherical conductor of radius r. Suppose it is suddenly surrounded by a negatively charged shell. The conductor will rush to balance out the voltage. However, this changing current ...
0
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1answer
19 views

When happens to the current during reversed biased?

The main working function of a half wave rectifier is to convert AC current to DC. My problem is to understand during the negative cycle. The above picture is time versus current. We can see easily ...
3
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2answers
167 views

How to calculate the resistance of a resistors in a grid?

I've found a lot of example of a grid where you want to total resistance of a grid. My problem is different. Let's say you got a grid of resistance (3x3) but you only have the total resistance between ...
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0answers
18 views

What transformation produces this kind of dual circuit?

What relates the following table of equivalences? Series $ V_{ac} = V_{ab} + V_{bc} $ Parallel $ I_{ac} = I_{ab} + I_{bc} $ Resistor $ V = \mathrm{R} I $ Conductor (the same) $ I = \mathrm{R}^{-1} ...
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0answers
28 views
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2answers
866 views

How does symmetry allow a rapid determination of the current between $A$ and $B$?

The following was originally given to me as a homework question at my physics 2 course: Consider the following circuit The difference of potentials between the point $V_{1}$and the ...
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0answers
22 views

About voltage sources in series [closed]

What is the reason of connecting batteries in series to obtain a higher voltage?
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1answer
48 views

Why Thevenin's theorem is being violated?

in the given picture we need to find the current flowing through the 3 ohm resistor. Applying KVL we can find the current as 4 amps but if we thevenise the circuit at terminal a-b then the current we ...
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1answer
37 views

Behavior of coil and resistance in DC circuit [closed]

I have a simple circuit of a coil parallel to a resistance and then in series with another resistance. I wanted to understand the behavior of this circuit so I ran a simulation, and what I noticed is ...
0
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1answer
165 views

What is the strength of the magnetic field required to penetrate an average human body?

Introduction Suppose you are an experimental nanobot researcher trial-ling a new form of medication that involves activation and control of nanobots within the cells of the interior of the human body ...
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1answer
16 views

Is peak voltage or peak current kept constant when we change resistance in an AC circuit?

I found online that Ohm's law still applies to an AC circuit and that $V_{peak} = RI_{peak}$. However, I can't seem to find anywhere weather an AC source will : Act as a voltage source and keep its ...
2
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0answers
65 views

Circuit theory paradox - Unexpected results [closed]

I recently studied capacitors and found out that there is something called 'ideal circuit paradox'. Searching Google I found that one can cannot find the potential difference between two points in a ...
0
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2answers
46 views

Why is there only a drop in potential energy when charges flow through a resistor?

First, I read that if you move a charge (say a positive charge) against an electric field, its electric potential energy increases because you're doing work to move the charge to that position. I also ...
3
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3answers
4k 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
43 views

Different voltage drops depending on the path

I was working through a problem in electromagnetic induction when I discovered that I have a fundamental ignorance of some sort that is puzzling me. Consider a circular wire, at rest, perpendicular ...
2
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1answer
32 views

Is it possible to measure the resistivity of something using A.C. Current and a capacitor?

I've read that A.C. current "passes" through a capacitor. Is it possible to use this and measure the resistivity of the medium between the plates? Any sources or links would be appreciated.
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2answers
236 views

Current on both sides of a capacitor

When a capacitor is connected to a DC circuit, what ensures that the current on both sides of the capacitor is the same? When charges arrive at one end of the capacitor they stop moving; presumably ...
-1
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1answer
19 views

Armature of electric bell [closed]

I want to know that why is the armature of the electric bell made up of soft iron ? I googled this out and everywhere it was written that it is because of its propert to aquire electromagnetism but I ...
0
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2answers
278 views

Close or open circuit?

A electric source provides a non electrostatic influence on the charges inside the source which pushes the positive charges from the negative terminal to the positive one. Does this happen when the ...
1
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2answers
4k views

How can be the neutral wire at 0 volts when current flowing through it?

Voltage is potential difference, and current flows because of voltage. So if the voltage is zero, how can current flow through the neutral wire.
3
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5answers
21k views

Current in series resistors and voltage drop in parallel resistors

When we have resistors in series, the current through all the resistors is same and the voltage drop (or simply voltage) at each resistor is different. Question 1: It is fine that voltage drop (...
7
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5answers
10k 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 ...
0
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1answer
121 views

How is a variable potential divider able to reduce current/voltage through a component to zero, unlike a variable resistor?

For example, the diagram in my text book shows a filament lamp, in series with a uniform resistive wire, which can have its voltage and current varied by moving the sliding contact, e.g., a ...
0
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1answer
114 views

Closing a switch in series with a capacitor

Suppose we have the following circuit: Such that for $t<0$ the switch M was open. If we close the switch at $t=0$ what will the voltage on the capacitor, $V_C$, be at $t=0^+$? What about $\dot ...
5
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2answers
252 views

What is the area in Faraday's law if we have only a piece of metal moving in a magnetic field?

If a piece of metal of length $l$ is moving with a speed $v$ in a region where there is a uniform magnetic field $B$ perpendicular to it, there will be a potential difference across its terminals ...
4
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3answers
3k views

General integral to find resistance

My question is: is there a simple and truly general equation for the resistance between two electrical equipotential surfaces?. Obviously, if so, what is it, and if not, why? It would be very ...
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votes
1answer
47 views

Resistor homework assignment: 7 resistors with connected triangles [closed]

I am a lost in how to solve this problem, since I don't how where to start. The questions doesn't inform any voltage or current, asking only the equivalent resistance of the circuit. All resistors ...