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

learn more… | top users | synonyms

0
votes
2answers
68 views

Kirchoff's loop law

Can any one provide me with mathematical proof of kirchoff's loop law? I am not able to understand from where to start.
0
votes
1answer
77 views

Comparing voltages of Parallel and Series circuits

There are two electric circuits. Resistor 1 ($R_1$) connected with resistor 2 ($R_2$) by series circuit $R_1$ connected with $R_2$ in parallel Each of the circuit has battery with emf and the ...
0
votes
1answer
54 views

Quadrupling Power in a Circuit

If I have a heating wire with resistance $R$ to be connected across a constant potential difference $V$, it would seem like cutting the wire into two (thus each having half the resistance) and ...
0
votes
1answer
55 views

Current in Parallel Circuits

For the parallel circuit below: Why is the current across the ammeter unchanged when the resistance of the variable resistor is increased? I've always learnt that current varies in parallel and ...
0
votes
0answers
57 views

capacitors - Square circuit of two capacitors charging in a changing magnetic field

I've been studying capacitors and DC circuits, and I received this question as part of my homework: The above circuit is a square circuit with side a. E and F are the midpoints of AB and CD ...
9
votes
2answers
1k views

How does my hand amplify an FM radio signal?

I have a gizmo that broadcasts an FM radio signal from my phone's headphone socket to my car's radio antenna. Sometimes, there's another station on the same frequency with a stronger signal and my ...
5
votes
4answers
8k views

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 ...
2
votes
2answers
938 views

Is the standard explanation for the ring launcher incomplete?

Related: Faraday's law in a ring The ring launcher is a standard introductory physics demonstration that I assume almost everyone has seen (if not, YouTube it). The explanation of why the ring is ...
1
vote
3answers
142 views

Is there charge build up before a resistor?

I understand that Kirchhoff's current law says that the current, $I$, is constant throughout a resistor, i.e. there is no build up of charge in a resistor. All charge going in to the resistor is the ...
1
vote
1answer
77 views

Exact Relation between voltage and current [duplicate]

I apologize before hand if this seems too naive. I'm having a really tough time understanding the relation between voltage and current. I read that 1 Volt is the amount of work done to move a $1As$ ...
2
votes
2answers
111 views

Is a Thomson's lamp physically realistic? [closed]

The Thomson's lamp is a philosophical puzzle that can be describe as follows: Consider a lamp with a toggle switch. Flicking the switch once turns the lamp on. Another flick will turn the lamp off. ...
0
votes
2answers
38 views

Power in a circuit why is V constant

In deriving the power of a circuit we can do the following: $$\text{P}=\frac{dw}{dt}=\frac{dQ}{dt}\frac{dw}{dQ}=\text{IV}$$ But this assumes that $V$ (since $w=VQ$) is a constant. Why can we assume ...
2
votes
1answer
45 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?
1
vote
1answer
280 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 ...
0
votes
1answer
615 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
votes
1answer
295 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
votes
1answer
68 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
votes
1answer
67 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 ...
0
votes
3answers
165 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 ...
1
vote
0answers
40 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
votes
1answer
594 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
votes
2answers
170 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? ...
1
vote
4answers
542 views

What is the difference between a circuit with a resistor and one without it in energy terms?

In Fundamentals of Physics (HRW), an equation is derived for the current in a circuit in terms of its emf and resistance by the 'Energy method'; that is, deriving $\epsilon = i \cdot r$ and saying ...
0
votes
3answers
507 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
votes
1answer
48 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 ...
1
vote
3answers
102 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?
1
vote
0answers
40 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
306 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
votes
4answers
331 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
votes
2answers
69 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
vote
1answer
100 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
votes
3answers
178 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 ...
0
votes
2answers
2k 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?
1
vote
1answer
46 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
votes
3answers
2k 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. $$\frac{1}{R_{ev}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}+\frac{1}{R_{4}}+\frac{1}{R_{5}}.......\frac{1}{R_{n}}$$ ...
0
votes
1answer
51 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 ...
0
votes
2answers
362 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 ...
1
vote
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?
2
votes
0answers
153 views

Why are ammeters used in series and voltmeters in parallel?

As I'm reading a course on electricity, this one says that an ammeter should be branched inline and not on a bridge. Can someone explain to me physically why we branch a amperemeter inline and a ...
-1
votes
3answers
140 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 ...
0
votes
1answer
48 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 $t=18$ ...
2
votes
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 ...
0
votes
1answer
60 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 ...
1
vote
2answers
742 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
votes
1answer
49 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
votes
1answer
480 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 ...
-1
votes
1answer
69 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
votes
1answer
143 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
votes
1answer
281 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 ...
1
vote
2answers
57 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. ...