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

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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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1answer
58 views

Drift velocity of electrons with changing area

What would happen with the drift velocity of a cylindrical resistor's diameter increases, with a given voltage between its terminals? According to the expression: \begin{align} ...
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1answer
117 views

Specific differential equation in RLC circuit

I have been studying differential equations in RLC circuits: specifically I am looking at a generator with fixed EMF $=E$,a capacitor $C$, an inductor with inductance $L$ and internal resistance ...
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1answer
29 views

Dependence of the Capacitance on the Material and Geometry of the Plates

I have two questions concerning capacitors: 1) We know that the capacitance of a capacitor also depend on the dielectric material inside as $C=$ $\dfrac{K \epsilon_0 A}{d}$ But what if the ...
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1answer
417 views

Power dissipation in circuits:Why is high voltage used in power lines?

I know this question has been asked before, but there is one doubt I still cannot clear. Power dissipation is proportional to $I^2R$. Does this not mean that it is also proportional to $V^2/R$? If ...
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1answer
104 views

Normal modes of two parallel $LC$ oscillators coupled via mutual inductance

Consider the circuit shown below. The two LC circuits are arranged in such a way that their mutual inductance M results in a coupling between the currents flowing in the two circuits. Find the ...
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1answer
77 views

Voltage across an inductor contradicts Lenz's law?

Imagine a simple circuit consisting of an alternating current source connected to an inductor. Assume they are connected in the following fashion: AC source - terminal A - Inductor - terminal B - AC ...
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1answer
109 views

A problem regarding equivalent resistance between two points [closed]

I came across this problem in a book which has solutions for all questions except this one. I can't get how to do this partly due my doubt whether the R and 4R resistors will get short-circuited or ...
4
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2answers
202 views

Voltage drop due to a resistor

I'm afraid this question is going to sound rather dumb but here it is: Suppose I have a very simple circuit: one battery and one resistor. The sum of the voltages in this circuit has to equal zero. ...
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1answer
89 views

What is the equivalent resistance of this bridge circuit?

I am trying but could not find any way of calculating the equivalent resistance of this circuit. Please help me. Should I use the Wheatstone Bridge equivalent resistance, the Y-$\Delta$ transform, or ...
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1answer
40 views

Why is the loop rule from circuit theory applicable for 'any' loop?

While proving Kirchoff's loop rule in class or any physics book, we take a simple one-loop system for the proof. In such a case, the current actually goes round the loop and the same current flows ...
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1answer
107 views

Can the electric field strength of a wire simply be calculated using the voltage / length formula?

Can the electric field strength of a wire simply be calculated using the voltage / length formula: Electric Field Strength = Voltage Across Wire/ Length of Wire I am asking about a wire with current ...
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0answers
27 views

Why is voltage input different from voltage output in a circuit?

This is more specifically, when performing the meter bridge experiment. The meter bridge experiment is an experiment in which using the meter bridge, a jockey, voltmeter, battery eliminator, you keep ...
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0answers
18 views

Is it possible that intermittent current is being passed in a circuit with loose connections at less than maximum capacity?

In a circuit, the wires may not have been connected properly and a connection is loose somewhere. Is it possible that intermittent current is being passed in a circuit at less than maximum capacity?
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0answers
21 views

Why is the current measured through a thin film increasing with time? (experimental question)

I'm doing an experiment: I'm thermally evaporating a metal in a vacuum onto a quartz (very insulating) substrate, between two gold contacts that I use to measure the current through the (growing) ...
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0answers
65 views

Energy of RLC circuit

If you are given a general differential equation for an RLC circuit, for example, $$L\left(\frac{d^2 Q}{dt^2}\right) + R\left(\frac{dQ}{dt}\right) + \frac QC = V\cos(\omega t),$$ which is a driven ...
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4answers
193 views

Application of Kirchhoff's laws in circuits with inductors

As we know,the Kirchhoff circuit laws are applicable for conservative electric fields. Now it is applicable for circuits where inductors are present but the field there is not conservative. So how ...
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1answer
384 views

The shape of the graph of the equation: $V= -r I + E$

I have recently collected data (for a school experiment) in order to measure the EMF and the internal resistance of a solar cell. The data complied with the equation: $V = -rI + E$, i.e. the voltage ...
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2answers
50 views

Calculating emf with and without resistance

A battery of internal resistance 2 Ohms is connected to an external resistance of 10 ohms. The current is .5 A. What is the emf of the battery? The correct answer is 6.0 V. When I calculated it like ...
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2answers
2k views

Why does the thickness of a wire affect resistance?

For small thicknesses of wire, it's pretty obvious why resistance affects thickness. (The electronics squeeze to get through). But after a certain thickness shouldn't the thickness become irrelevant? ...
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1answer
101 views

Voltmeter readings at different points in a circuit

I have a circuit with a 6 volt battery and 2 resistors A and B in that order.A has a potential drop of 2 volts and B has a P.D of 4 v. which means every electron moving across the resp. resistors ...
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1answer
72 views

Understanding frequency of a signal

I'm trying to understand how can one transmit different signals on a same copper wire using different frequencies. How does the electrons actually interact with the frequency? And how does the ...
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1answer
48 views

Why is the current in an electric circuit constant?

Considering electrostatics, suppose we have two charges of equal value and opposite sign and we put electrons along the road between them: We know that the electrical force or field is different from ...
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2answers
195 views

What is zero impedance in AC circuit?

If a capacitor is connected with an inductor, then because $$Z=\frac{1}{j\omega C}+j\omega L,$$ the Z may be zero. Does that mean when I apply a voltage, the current will be infinite large? What's ...
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2answers
33 views

Finding power in series circuit

A resistor of resistance 12 ohms is connected in series with a cell of negligible internal resistance. The power dissipated in the resistor is P. The resistor is replaced with a resistor of resistance ...
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1answer
20 views

N-type semiconductors and the number of holes?

Let us say we have Germanium which has been doped with antimony. Antinomy has a a fifth valence electron not involved in bonding. Is this electron in the valence band? I ask because all texts on the ...
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1answer
56 views

Can someone please explain impedance matching and wave reflection?

I'm reading Wikipedia's article on impedance matching (http://en.wikipedia.org/wiki/Reflections_of_signals_on_conducting_lines) and this just seems so foreign to me. 1) What does it mean for a ...
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1answer
49 views

How to calculate current flowing down a wire connecting charge to ground

If charge Q is connected to ground through a wire, how would you calculate the current that flows as a function of time? No other information is given. I have not seen this type of problem in the ...
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2answers
50 views

Simple confusion about parallel resistors

that tension generator has 1V , Can i just ignore it and apply the parallel resistors theorem R= R1R2/R1 + R2 ? and replace R1 and R2 by R? if the generator wasn't there this would be easy
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1answer
51 views

Can Thevenin voltage ever be negative?

So in context of Thevenin's and Norton's theorem, can Thevenin voltage $V_{th}$, as in http://en.wikipedia.org/wiki/Thevenin_theorem, ever be negative? I know that $R_{th}$ can be negative, but never ...
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2answers
130 views

Why isn't resistance proportional to distance squared

Here we have a wire. At both ends there is an equal and opposite field caused by a chemical reaction. So, if we decrease or increase the distance between the two points, the strength of the field ...
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1answer
48 views

Getting maximum power/brightness from 5 lightbulbs with different resistances [closed]

Hi I am trying to figure out the best way to arrange 5 lightbulbs to get all of them to have the maximum brightness with a 30V battery. The 5 five lightbulbs have different resistances: 3ohms, 6ohms, ...
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2answers
69 views

How to deal with a $0\Omega$ resistor connected in parallel? [closed]

There is a side without resistance, what is the equivalent resistance? Can anyone help me solve this?
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3answers
75 views

I wonder why I cannot charge a capacitor with alternating current?

Why can't I charge the capacitor with AC? How do the plates block the flow of electrons with DC but not with AC. Somebody told me that the DC is blocked by the capacitor, so the capacitor gets ...
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2answers
101 views

$V = V_1 + V_2$ confusion? Why is my “proof ”incorrect? [closed]

Why isn't $V= V_1 + V_2$? $V=V_a - V_c = V_a - V_b + V_b - V_c$, $V_a - V_b= V_1$ and $V_b - V_c = V_2$ Doesn't that prove that $V = V_1 + V_2$? Regardless of $V_3$, If i'm wrong , is there a way ...
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2answers
65 views

Is $V= V_1 + V_2$? horrible question but im confused [duplicate]

So yeah , the answer seems true but i'm very skeptical about it since D3 is in the middle
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3answers
209 views

How do electrons actually move in a circuit?

Last year, we were taught about electricity, about how electrons in a closed circuit. But as our teacher had not taught us about electric fields yet, she gave us a simplified model of motion of ...
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2answers
69 views

Parallel and series circuit problem

When two resistors, each of resistance 4.0 ohms, are connected in parallel with a battery, the current leaving the battery is 3.0 A. When the same two resistors are connected in series with the ...
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1answer
51 views

How similar is comparison between the principle behind Newton's Cradle versus AC Current moving down a transmission line?

Anyone who has taken high school physics has seen the following assembly. You drop one ball from the left hand side and the ball from the farthest right hand side gets knocked away. This is to ...
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1answer
42 views

AC circuit analysis: Why does current have the same frequency as the voltage?

The above example we have a 50hz AC voltage source. Why is that when we solve for I, I must have frequency of 50 Hz? Is there any phyiscal (non-mathematical) reason to explain this? Thank you
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1answer
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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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4answers
312 views

What happens in a circuit, when the wire and the battery are superconducting. And shorted

When a wire with no resistance is connected to the terminals of an ideal battery, will a current exist in the circuit? If a capacitor is added to the circuit, will it be charged by the battery or will ...
4
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3answers
11k views

Different batteries connected in parallel

If we have 2 batteries one of emf x and the other is of emf y and we connect them in series we get an effective emf of x+y. But what if we connect them in parallel, how to calculate the emf now?
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2answers
70 views

Why doesn't a resistor dissipate reactive power? [closed]

Is there a (preferably microscopic) explanation for why a resistor does not dissipate reactive power?
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2answers
3k views

Voltage and Current in transformers

In transformers, the ratio of the voltages equals the ratio of the turns - so double the output coil's turns and the output voltage doubles. Then, in order to conserve energy, current halves. This ...
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1answer
33 views

Is real voltage always the real part of complex voltage?

If I have a complex voltage $V_z$ is real voltage $V$ (i.e. the voltage used in the normal ohms law and the voltage we normally talk about) always given by $V=Re(V_z)$. Does the same apply to current? ...
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2answers
53 views

Finding the current in a parallel circuit [closed]

Two resistors are joined as shown. The top resistor receives a current of 3 A. What is the current in the other resistor? What is the current that enters at junction A? I'm confused on how the two ...
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1answer
70 views

Am I solving this basic Kirchoff's current law and Ohm's law problem correctly?

After moving onto some of the practice textbook exercises in the section covering Kirchhoff's current law and Ohm's law, I came across a problem which evades my best attempts at solving it. Using ...
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1answer
52 views

What's wrong with this solution to freshman textbook example for Ohm's law and Kirchhoff's current law?

I'm a freshman taking an introductory course on circuit theory and I've run into a bit of trouble working through a textbook example practice problem. Unfortunately, it only lists the answer and not ...
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1answer
60 views

Current in an RC circuit inside in a magnetic field

Does my question make any sense? Context: The capacitor is charged with charge $Q_0$. There is a magnetic field $B=B_0 \hat{z}$ perpendicular to the monitor's screen. The length of the (AB) wire is ...