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

learn more… | top users | synonyms

0
votes
1answer
2k views

How to calibrate an Ammeter?

Calibrating an ammeter is tricky thing to do. The obvious way would be connecting it to another good ammeter and see if they get the same result. However, people have been telling you can use a ...
0
votes
1answer
4k 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 ...
3
votes
1answer
240 views

Electric circuit. Slight problem with the sign on voltages

Translation first! The figure shows an electric circuit. a) Use Kirchhoffs 2.law on the part-circuit abed and show that $I_3$ = 0,50A. b) Explain that $I_2 + I_5 = 2,0A$. Use Kirchhoffs 2.law on the ...
4
votes
2answers
136 views

What exactly is ''electric energy''?

If the two fundamental types of energy are kinetic and potential energy, is electric energy simply the kinetic energy of charge carriers? Also, is the statement "A cell converts chemical potential ...
0
votes
2answers
60 views

Back $emf$ and power?

The formula relating current to back emf is $V-E=IR$ where $V$ is the source pd and $E$ is the back Emf. Thus it can be seen that as the back emf increases the current decreases. But what is the ...
-1
votes
1answer
38 views

High Current at first and then steady from a battery

I just came up with a question, When a battery is connected to a circuit, the current first suddenly peaks up and slowly goes down to a steady value. Why is it so? I have not actually observed this, ...
-1
votes
1answer
63 views

Resistances connected in series

When resistances connected in series then why through each resistances the different potential difference occurs?
1
vote
1answer
143 views

Calculating decibel gain and loss

I'm doing a mobile/wireless networking subject and the physics aspect is giving me some trouble. I'm mainly confused about the conversion of dB, dBm and dBW and how to calculate the gain/loss from an ...
1
vote
1answer
71 views

Do I understand impedance correctly?

$$Let\quad \vec { Z } =R+Xj$$ If $X>0$,then the impedance is lagging (current lags behind voltage).If $X<0$, then the impedance is leading (current leads voltage or more accurately, voltage lags ...
2
votes
1answer
322 views

Energy conservation when capacitor charges in a zero resistance circuit

We know that when a capacitor charges from a source $E$, it stores energy of $E=\frac{1}{2}QV $. This is derived without taking into consideration any resistances present in the circuit. We also ...
16
votes
4answers
3k views

What's the physical meaning of the imaginary component of impedance?

As you know, impedance is defined as a complex number. Ideal capacitors: $$ \frac {1} {j \omega C} \hspace{0.5 pc} \mathrm{or} \hspace{0.5 pc} \frac {1} {sC} $$ Ideal inductors: $$ j \omega L ...
0
votes
0answers
180 views

Power wasted and power delivered?

If a power source is supplying a current I and a voltage V, that travels to its destination through resistors of restance R is the power delivered at the destination = $VI - RI^2$, where $(Pi=) VI$ is ...
1
vote
1answer
86 views

How can current be a smooth curve?

The following is a graph of the current across some circuit element: Note how the current is treated like a smooth continuous function. Even in the analysis of things (i.e. analysis of the ...
3
votes
2answers
162 views

How to model “Doppler Distortion” of speakers?

Simple Model w/o Doppler I have a speaker driven by an electrical signal. The pressure at the sampling point is some linear operator acting on the input signal: $L[ s(t)]$. Where $L$ combines the ...
1
vote
1answer
74 views

Circuits and Power [closed]

"The diagram below represents a simple circuit composed of 5 identical light bulbs and 2 flashlight batteries. Which bulb (or bulbs) would you expect to be the brightest? a) V only b) V and W ...
1
vote
1answer
142 views

Batteries and fields?

Batteries generate fields in wires that essentially cause the movement of electrons. I think of batteries as two charged plates that essentially contain a mechanism between them to move electrons from ...
2
votes
1answer
125 views

Sign convention for EMF

When we define the field generate by EMF, why there is not negative sign in $\mathcal{E} = \oint \vec{E} \cdot d\vec{l}$? Usually we talk about potential, there should be a negative sign, right?
0
votes
1answer
121 views

Ohms Law Voltage/Potential Difference [duplicate]

Three 2.0 Ω resistors are connected in series to a 12 V battery. What is the potential difference across each resistor? � This question requires Ohms law because V is needed right? So I would use I = ...
3
votes
2answers
2k views

Round bulb and Long bulb in Series Circuit

If you have a series circuit with a battery, one round bulb (with thicker filament), and one long bulb (with thinner filament), the round bulb does not light up and only the long bulb lights up. ...
1
vote
3answers
683 views

How “earthing” electricity work?

I made a simple bulb-battery circuit and then I cut one of the wires and attached both ends to cemented floor, the bulb didn't glow, this means cemented floor is a ...
2
votes
1answer
385 views

Which direction does the electron move?

If my phone is charging that means it's mass increasing by this Youtube video. Now if an current is flowing from the power station to home, does it mean that electron is flowing from house to the ...
0
votes
5answers
19k views

Why does voltage remains same over Parallel Circuit

Why does voltage remains same over parallel circuit. If a resistor is connected in the circuit some of the charge should be transformed into heat and make a lack of charge after the resistor (in my ...
0
votes
1answer
99 views

Voltage across parallel combination on adding another resistance

Suppose we have a battery with terminal PD $V$ connected to an external resistor of resistance $R_1$. Now if another resistor say $R_2$ is added in parallel to $R_1$ , does the potential drop across ...
0
votes
2answers
89 views

Finding the voltage of an inductor in a RL series circuit [closed]

Here is the solution: This assigned question is an odd one since it doesn't seem to have anything to do with phasors which is the chapter I am currently studying. I know that that the phase ...
1
vote
1answer
49 views

Circuit analysis: Two nodes as one?

Can I treat these two nodes in the center as if there were only one node connecting these four components?
0
votes
3answers
196 views

Weird resistor patterns [closed]

I came up with the following question: The vertices of tetrahedron ABCD are all connected by 1-ohm resistors. What is the total resistance between A and B? I haven't the faintest idea how to ...
0
votes
0answers
163 views

Thermal noise from capacitor; circuit analysis

I'm trying to model the thermal noise from a capacitor. The capacitor is connected directly into an amplifier with resistance $R_{A}$ and capacitance $C_{A}$. A noisy capacitor is modelled as a ...
1
vote
3answers
7k views

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 ...
0
votes
2answers
108 views

Is this way of solving Thevenin theorem correct?

This thevenin theorem is really giving me a headache, and I've really searched many sources in the internet but they confused me more and more. Take this as an example: The guy in the above link ...
0
votes
1answer
976 views

Wheatstone bridge Capacitor,Dead Capacitor [closed]

I want to know that if in a Wheatstone Bridge ,that is made of capacitors only we have this condition $c_1c_3=c_2c_4$. The $c_5$ capacitor would be dead and it's voltage would be zero? Actually I ...
0
votes
0answers
79 views

Charge Amplifier response and frequency response [closed]

I am getting ready for my final and have completed everything on my study guide except for two questions I cannot figure out. Here is the first question: I have gone through all my lectures and ...
2
votes
0answers
73 views

How do the different types of energy apply to voltage in a circuit

I was just wondering what happens in a circuit in terms of different types of energy transformations. If you apply a voltage to a circuit then electrons start moving (very slowly). Since the electrons ...
1
vote
1answer
174 views

Kirchoff's rules and RC circuits [closed]

You can view the image bigger: http://i.stack.imgur.com/4moUP.png I'm studying RC circuits and I can't understand the part when we use Kirchoff's rule. When working with batteries, when we're ...
1
vote
1answer
92 views

If you have $N$ 1ohm resistors, how many distinct equivalent resistances can you create?

If you have $N$ 1ohm resistors, how many distinct equivalent resistances can you create? Assume that only parallel and series and mixture of them is allowed and no bridging between two parallel ...
0
votes
1answer
94 views

Understanding Counter - EMF?

When an coil rotor is moving around a magnetic field there is -V induced to resist the input V. Let's take an example, a 12 V DC motor induces -10V, and the actual running voltage is 2V. If there ...
0
votes
2answers
517 views

How do I combine three resistors which are in parallel with each other?

For this circuit (a and b are connected by a battery), Will I be able to find the total resistance of the circuit by adding resistors that are in series and combining resistors that are in ...
1
vote
0answers
620 views

How does a Photocell/Photoresistor work? [closed]

I'm just curious highschooler beginning an interest in electronics and this concept of light detecting resistance component is really intriguing to me. I assume it's an application of the ...
0
votes
1answer
41 views

The value of current and voltage in a circuit

The picture is just for example. I don't know why $i$ and $i_1$ have different directions and $i+i_1=0$ according to KCL. Also, the value of voltage at each element. I mean in why the $V$ of the end ...
1
vote
5answers
862 views

How does series circuit differ from parallel circuit?

Why does same current $I$ flow in the series circuit but it isn't the case with resistors in parallels?
0
votes
3answers
92 views

electric current in parallel circuit [closed]

If I have a parallel circuit with two resistors ($R_1=48 \Omega$ and $R_2=16 \Omega$) - and $R_1$ has a $0.1 A$ current running through, is it possible to calculate the current through $R_2$ without ...
1
vote
0answers
256 views

Power dissipated through resistor in RC circuit with charged Capacitor [closed]

so here's the problem: A simple RC circuit where the capacitor has been charged, and two resistors are in parallel configuration. How does one find the power (as function of time) through any of the ...
1
vote
3answers
897 views

Why do both plates of a capacitor have the same charge?

How do we know that both plates of a capacitor have the same charge? You could argue conservation of charge, but I don't see how conservation of charge implies the charge on both plates is the same. ...
6
votes
3answers
3k views

What happens if I throw a battery into water?

Today I have by accident thrown a AAA battery into a bucket of water. I fished it out of the water immediately (within 20 seconds or so) and nothing notable had happened and the battery is still full ...
-1
votes
2answers
449 views

capacitor in ac and dc circuits

In a dc circuit work done by battery=QV while energy stored in capacitor =(QV)/2 loss in energy=(QV)/2 While a capacitor in ac circuit has a no power loss.why is it so? Shouldn't heat be lost in ac ...
0
votes
1answer
816 views

Changing the resistance of a circuit

I am wondering, when we change the resistance in a circuit, does the voltage tend to increase or the ampere decrease? More specifically, under what conditions does what happen? E.g. If we have a ...
2
votes
1answer
114 views

Do batteries lose charge?

Say I have a charge of +q and -q on the positive and negative terminals of a battery. If I connect wires to each terminal, but don't connect the wires (essentially creating an open circuit), the ...
3
votes
4answers
1k views

Is a capacitor in an open circuit charged?

Say I have a circuit consisting of a battery, a wire, an open switch, and a capacitor. The circuit is open since the switch is open. My book says that the capacitor will only be charged when the ...
2
votes
1answer
135 views

Can resistance of wire be ignored

I was doing some physics homework involving direct current circuits and resistors in series, and I started to question the accuracy of the following property of resistors in series, namely that the ...
2
votes
2answers
2k views

How to Determine the voltage polarity of inductor in a circuit? [closed]

The Voltage polarity across the inductor is same as that across the capacitor since both are in parallel and the voltage across them must be same. But when Inductor, capacitor and resistor are ...
6
votes
4answers
1k views

What is the current of a capacitor when the derivative of voltage is undefined?

This is from the textbook I am reading: I know this equation for capacitors: $$i=C\cdot \frac { dv }{ dt }$$ Here is my question: how can diagram (a) be allowed if the derivative of the voltage ...