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

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1answer
46 views

Can a transformer transfer all power?

How can the transformer transfer exact power from primary winding to secondary winding if there are core losses, eddy current losses and hysteresis losses?
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1answer
350 views

Question on Shockley's equation for FETs

I'm currently studying FETs (Field Effect Transistors) in Navy school. What I know so far is that in FETs, $V_{gs}$ is reversed biased, creating a depletion zone. What this means in plain English is ...
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1answer
861 views

Draw a Schematic Diagram of Ammeter Connected in Parallel to explain difference between the diagram of a parallel and series connection

I know that voltmeters are commonly in parallel and ammeters are commonly in series. I believe that the voltmeters in diagrams 2 are actually in series. How am I wrong? ![For example][1] In Diagram ...
4
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1answer
447 views

“Bump and Go” toy car mechanism [closed]

Can anyone please explain how the bump-and-go mechanism works in "old-school" toy cars? It's the one that uses a single swivelling wheel in the front, and when resistance is encountered (due to the ...
0
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1answer
75 views

How to understand this circuit? [closed]

I don't if here is the right place to ask it, but there I go: I'm studying about Ohm's Law, and the following problem perplexed me. Ps: The answer is It = 11mA and Ur = 41V It want to know the Ut ...
0
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1answer
89 views

Analyzing the voltage output of clampers

Let us say that we have the following negative clamper circuit with a 50 volt peak-to-peak square wave as an input: The output from the circuit is a -50 volt square wave with the peak positive ...
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3answers
272 views

Explaining the current flow of the positive shunt clipper (diodes)

I am currently studying clippers or parallel limiters in the Navy and I was wondering if someone could clear up a few things for me. Here is a picture that fits my description: A clipper has a ...
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0answers
47 views

Why didn't all three of my electrical fuses ignite? [closed]

I built a rocket that used 3 x solid fuel motors. To ignite them I used 3 electrical fuses, which are basically a thin filament of wire which heats up when given enough voltage. Only 2 of the 3 fuses ...
3
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1answer
642 views

$Q$ factor of parallel RLC circuit in series with a capacitor and resistor

I know that for parallel RLC circuits, the $Q$ factor is given by: $$ Q = R \sqrt {\frac{C}{L}} $$ But now suppose it is connected in series to a resistor $R_2$ and capacitor $C_2$. Would the $Q$ ...
0
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2answers
203 views

What is the potential difference across the lamp? [closed]

For all problems, assume that the battery voltage and lamp resistances are constant, no matter what current is present. A 75-W lamp is connected to $125 V$. What is the current through the lamp? ...
0
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3answers
703 views

RL vs RC circuits

I find it difficult to understand as to why current behaves differently in an RL and an RC circuit. At time $t=0$, in an RC circuit the current is maximum, whereas in an RL circuit its $0$. Why is it ...
0
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1answer
52 views

Graphs of electric quantities for cell with internal resistance [closed]

A cell of EMF $E$ and internal resistance $r$ is connected to an external resistance $R$. Draw graphs to show the variation of (a) $E$ with $R$, and (b) terminal potential difference $V$ of the cell ...
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3answers
141 views

How to use phasor method for analyzing electrical circuits when current has DC components

So let's say that we have a electrical circuit with a current source that is sinusoidal, but has DC offsets. How then do we convert this $i(t)$ into phasor $I$? Or is this generally impossible?
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0answers
43 views

Finding the current in the circuit [closed]

I don't understand the logic of finding a current. I think I can find it using nodal analysis or mesh analysis, but I want to understand the method. Here is an example: I want to find $I_0$.
2
votes
2answers
471 views

What causes a resistor to heat up?

In the following video clip at 2:10, http://www.youtube.com/v/YslOUw5oueQ , Professor Walter Lewin talks about a misconception people have that the energy going through a wire to a resistor is in ...
2
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4answers
423 views

Why doesn't current flow when the wire is open?

I realize this may be a hard to answer question but we are currently studying current in our school. One thing that struck me was why the heck doesn't it flow when the wire's closed? When you connect ...
0
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2answers
90 views

Since no current flows, the voltage is 0?

I didn't understand that , "Since no current flows in the ammeter the potentioal difference is 0 " How did they conclude that? I made this example So i made this example in paints , (R square ...
1
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1answer
123 views

Johnson-Nyquist noise for resistive element with temperature gradient

In Nyquist's 1928 paper, Thermal agitation of electric charge in conductors, the voltage noise for a resistor is derived assuming a circuit in thermal equilibrium and one temperature. How does the ...
4
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3answers
214 views

Voltage drop = more electrons on one side of resistor

I have been asking myself this question for a long time now. Suppose we have two resistors in series connected to a voltage source. Simply put, does the voltage drop on each resistor mean that there ...
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2answers
4k views

Definition of Equivalent Resistance [duplicate]

Is the equivalent resistance of two parallel resistors the resistance of the individual resistors or the sum of their resistances? Is the $R_e$ of two series resistors their sum?
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1answer
59 views

Explain why the frequency cutoff for RL circuits is given by $\frac{R}{2\pi L}$

I am studying low and high pass RL filters for Navy schooling. I need someone explain why the frequency cutoff is $fco = \frac{R}{2\pi L}$ mathematically. From my oscilloscope lab results I got the ...
2
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3answers
3k views

Why is equivalent resistance in parallel circuit always less than each individual resistor?

There are $n$ resistors connected in a parallel combination given below. $$\frac{1}{R_{ev}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}+\frac{1}{R_{4}}+\frac{1}{R_{5}}.......\frac{1}{R_{n}}$$ ...
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1answer
55 views

Discharging capacitor

When the capacitor is fully charged and the switch as it B, how can we apply KVL at that loop to reduce the equation to (-IR)? Why is it negative? At time = 0 is the current not zero? And it will ...
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2answers
489 views

Greatest and Least Resistance and Current Characteristics of Parallel vs Series circuits

Which type of circuit would have the greater resistance? Which type would have the greater current? and Why? My book says that parallel has the greater resistance than current as parallel wiring if ...
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1answer
33 views

Make a circuit so that it heats water as rapidly as possible

To do this I understand that we need to create the greatest power. What I don't understand is why would we need to use a parallel circuit instead of a series circuit to create the greater power?
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3answers
189 views

Voltage in a parallel circuit [duplicate]

Why is voltage same across a parallel circuit? I mean what makes the voltage remain same across two resistors connected in parallel? If an electric heater is connected in parallel with a bulb and ...
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1answer
60 views

Negative charge on capacitor, Kirchoff differential equation with step function

I'm solving a differential equation of the form $$200q'+\frac{200}{3}q=3U_o-6U_6+3U_{12}$$ Where $U$ is the Heaviside step function. $q(0)=0 [Coulombs] $ After solving it, I get that at time $t=18$ ...
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5answers
1k views

Is voltage difference always proportional to its derivative?

We write, because of Ohm's law: $$V=RI(t),$$ but also we have $$C\frac{dV}{dt}=I(t).$$ From the first equation we deduce that $V\propto I$ and from the second $\dot V\propto I$. So we can conclude ...
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1answer
69 views

Questions about the formula used to determine inductive reactance and $Z_t$

I am currently on the inductors unit in my Navy schooling and I have two questions about these formulas that I learned about. As I'm aware, the ability of an inductor to concentrate a magnetic field ...
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2answers
760 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 = ...
0
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1answer
51 views

Why is the voltage negative?

What I don't understand is why the the two voltage sources are subtracted when working out the emf for part a, The graph does not show the orientation of the solar panel so I thought I was to ...
0
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1answer
583 views

Determining energy stored in capacitor and inductor in RLC circuit

I've been stuck on the following homework problem for a few hours now with little progress. As you can see, it's a relatively simple RLC circuit with a couple independent sources and a ...
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1answer
74 views

how can we apply the formula p=VI in power transmission lines?

i mean we don't know the value of voltage across the power lines...we just know the potential at which it is generated which is not the potential difference across its ends..say electricity is ...
0
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1answer
186 views

Why the bulb does not glow in this configuration of batteries?

I connected a bulb to a battery positive terminals with positive and negative terminals with negative . It glows as it should but when i connect the positive terminal of the same bulb to the positive ...
2
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1answer
459 views

Calculating Boltzmann constant using semiconductor

My task from the latest laboratory exercise in physics is to calculate Boltzmann constant from known temperature, current and voltage. We were given this circuit: By changing the resistor value, I ...
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2answers
69 views

Sign conventions in Devoret Les Houches course on quantum fluctuations in electrical circuits

In this article on p. 364 Devoret writes the "equations of motion" (using KCL) for the electric circuit shown on p. 363. He uses flux instead of voltages. The sign convention he uses, as shown on p. ...
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1answer
68 views

Can we double the electric energy?

If I have $x$ amount of electrical energy and convert that into mechanical energy using an AC Motor, and then convert that energy back into electric using an AC generator, will the amount of energy ...
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1answer
66 views

2 simple Generators = Im lost (intensity) [closed]

What happens? we have 2 Generators and 2 intensities, when I2 and I3 come together (they have opposite sides ) what happens? I tried writing down the voltage relations but I'm stuck because I don't ...
2
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4answers
352 views

Justification of root mean square [duplicate]

In the top answer to the question Why do we use Root Mean Square (RMS) values when talking about AC voltage, the following was stated: This RMS is a mathematical quantity (used in many math ...
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3answers
6k views

Is it safe to use any wireless device during a lightning storm?

I need "educated" reasons whether it is safe to use any wireless device during a lightning storm. Most people said don't use it but they cannot explain why.
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1answer
119 views

Voltage divider example [closed]

I have the following voltage divider circuit: Now, my goal is to find U_{L}. Altough, I know already the solution (U_{L}= ...
0
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1answer
85 views

Solving for current in a circuit problem (image included)

I need to find $I_{R_2}$ and I need someone to explain why $I_T = I_{R_1} = 1 mA$. I thought that we were supposed to use the fact that $I_T = I_{R_1} + I_{R_2} + I_{R_3}$: ! I have solved for $R_T ...
1
vote
1answer
52 views

Capacitors in Series and Parallel [closed]

I'm working on a physics project and we're disagreeing on how to analyze a circuit. I think the circuit should be $(1/c_1 + 1/c_2)^{-1} + c_3$ and other people in my group think it should be $((c_3 + ...
0
votes
1answer
45 views

What is the smallest resistance that can be used in a 5 V circuit if the resistors available are rated for 1/4 W? [closed]

What is the smallest resistance that can be used in a 5 V circuit if the resistors available are rated for 1/4 W? What is kind of throwing me is that it wants the "smallest resistance that can be ...
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vote
3answers
197 views

Explain why we use this formula to calculate total resistance [duplicate]

Why do we use this formula to find the total resistance? Lets say we have three resistors in a parallel circuit $$R_t = \frac{1}{\frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3}}$$ Where does it come ...
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1answer
66 views

What is the ohmic value of a resistor that will dissipate 1 W when the voltage across it is 2 V?

I've been learning about Ohm's and Watt's law throughout this chapter so I'm already familiar with substituting Ohm's Law for part of Watt's law to get values. But nowhere in the chapter did it go ...
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1answer
962 views

What is the power in this circuit if the voltage is doubled?

I'm actually going ahead in the book (DC Circuits) so this isn't really homework but I figured the tag was appropriate....the name of the chapter is Ohm's Law and Watt's Law. Problem: Calculate ...
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2answers
437 views

How can there be current if all paths have same potential difference

I am learning about circuit analysis now, but there is something that I can't wrap my head around. Imagine this simple circuit: ...
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2answers
150 views

Voltage and resistors

I've read in many books and through many answers on this and other sites about this concept. Now I'm not sure what to "believe". In the subject at my university, we are taught that conducting wires ...
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4answers
2k 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 ...