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Questions tagged [electric-circuits]

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

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How does a load/resistor affects a Transformer?

If a resistor is connected on the secondary let's say 2 Ohms, this would have an overall effect on the primary & secondary circuit of a Transformer. It is obvious that the resistor would affect ...
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51 views

Why doesn't a capacitor oscillate like a pendulum around equilibrium when discharging

Why doesn't a capacitor behave like a swinging pendulum when discharging? Please note that I'm not asking about solving the differential equation, but rather about how we are constructing it. I have ...
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1answer
30 views

Which types of collisions contribute to electrical resistivity?

Do electrons only bump with other electrons in a circuit and that only causes resistance? Or do they bump with the nucleus as well? Here's a post I have been studying recently: The path of a ...
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53 views

Why did a 12V battery affect my motor more than two 9v batteries in series?

In class, we made a coil of wire and used it to make a simple electric motor with a magnet. I put two square 9v batteries in series for a total of 18v to power the motor. I then used a larger 12v ...
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4answers
59 views

Why do we use dielectric materials in a capacitor?

Okey first of I know dielectric materials used in capacitors to insulate and polarize due to electrical field created by two metal plates and then when you connect this stored energy to a system you ...
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3answers
63 views

Why is the current same after and before passing through a resistor? [closed]

•Why is the current same after and before passing through the resistor ? •Why is a voltage drop across the resistor ? Explanation in terms of electron flow and electric field will be really helpful. ...
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2answers
46 views

The importance and the role of a switch in an electrical circuit

There is this simple test: Three identical bulbs are connected in the circuit illustrated in the figure. When switch $S$ is closed: a] The brightness of $A$ and $B$ remains the same, while $C$ goes ...
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4answers
665 views

How does resistance convert voltage to current? [closed]

This is a statement that I read mainly on books about electronics. Could someone explain why after the resistance current is what makes things work and not voltage? Example from the Art of ...
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1answer
53 views

Is internal resistance of cell part of the equivalent resistance of the network of resistors?

Do we include the internal resistance of cell while calculating equivalent resistance of network? Take, for instance, the question given. Do we include the 1 ohm internal resistance while calculating ...
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4answers
41 views

Find relationships between the voltage difference across capacitor and resistor

I'm trying to learn kirchhoff's law. but im stuck on how to solve for a circuit that has both a resistor and a capacitor. How would you proceed?
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2answers
36 views

For a real battery, why is two identical bulbs in parrallel slightly more dim than just one in series

Image for reference: $$\begin{align} &r = 0.8\,\Omega\\ &\mathscr{E} = 1.5\,\mathrm V\\ &A = B = 6\,\Omega. \end{align}$$ The current when the switch is open, the only other resistor is ...
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2answers
60 views

Why in a DC series Circuit do bulb attached in parallel to highest resistance glow brightest? [closed]

I was performing an experiment in which there were five resistances connected in series and then I connected a bulb with each of the resistance. Each bulb was connected in parallel to each resistance ...
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Question about full wave bridge rectifier

Sorry if this is a stupid question, what I know is when a diode is forward biased, it conducts current, when it is reverse biased, it acts as an open branch if its $ PIV \geq V_{in}$ But in this ...
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1answer
47 views

LC-circuit and the current

A capacitor and a coil are charged in the LC circuit. When the circuit switch is closed, the current starts to flow. In theory the oscillations and the current do not deteriorate, but why in reality ...
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2answers
56 views

Differential equations for the LC circuit

On wikipedia one can find that the DE for an LC circuit is given by $$\ddot I+\frac{1}{LC}I=0$$In one of my papers however I found the equation $$\ddot Q+\frac{1}{LC}Q=0$$ and I've been confused by ...
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1answer
56 views

Resistor Capacitor circuits

I am a high school physics teacher and came across some issues today that I am unable to explain. We made a circuit with an $11$ V power source connected to a $100~k\Omega$ resistor and $100~\mu F$ ...
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1answer
27 views

Direct current electric circuit

Why when I reverse one of the three batteries in a torch light, the bulb does not light up? The three batteries (one of them is reversed) and the bulb suppose to form a closed loop. According to ...
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1answer
24 views

Why do we subtract the voltage of the resistor from the emf voltage to find the terminal voltage?

I attached an image of a question from homework. I calculated the current in step 1) and then I calculated the voltage of the resistor. But why do I need to subtract that voltage from the emf voltage ...
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1answer
72 views

Where does the sound we hear from short circuits come from?

Title is self explanatory. Whenever I see or watch a short circuit happening, there is always a humming/buzzing sound going on (e.g., the sounds we hear from this short circuit compilation video). ...
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2answers
55 views

What is the direction of the electricity flow in a DC circuit?

I know that in AC, the direction of the flow of electrons is constantly changing, but this question is for a DC circuit like an LED with a battery. Does current in such a circuit flow from the - side ...
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1answer
59 views

Doubt while simulating electric circuits

Today, I was simulating DC electric circuits just for knowledge and fun using PhET interactive simulations. But I'm having trouble understanding these circuits which I made. I think that both these ...
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2answers
64 views

How can AC current pass through an open circuit?

I think for example for oscilloscope what gets signal just in one wire and how can even ac go through only one wire?
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1answer
68 views

Proving a theorem about the average value of a function over a specific region

Let's say transient phenomenon in a function. A transient phenomenon is defined as: "A transient event is a short-lived burst of energy in a system caused by a sudden change of state." So, for ...
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1answer
42 views

What do $I_{x2}$ and $I_{x3}$ represent in this Circuit? [closed]

I thought it would be Ix2 = I2 or Ix2 = 2I2. if that makes sense. The question asks for Voltage across R2 but i dont want an answer, i just need to know what those two symbols stand for so i can get ...
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1answer
26 views

Resolve The Envelope Detector Circuit

I was working on a little project and I was wondering if the envelope detector circuit could be resolved analytically. Let me explain. The circuit is the one shown above, I know the values of $C$, $R$...
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2answers
51 views

'Why don't electrons accelerate in a circuit' Confusion

https://physics.stackexchange.com/a/18806 Apparently he said 'at the same time', so when the electrons are 'pushed' by the electric field it is 'blocked' by the resistance simultaneously, if he said ...
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2answers
33 views

Voltage when lamp burns out [closed]

In the question below, shouldn't the voltmeter read zero V because the circuit is broken and there is no current flowing? (the answer in the text is 12v)
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3answers
73 views

Why doesn't the flow electrons occur in a broken circuit?

Take a battery and connect a small led bulb across it with the help of two wires. The bulb will glow, but if I cut a small piece of wire from any part of the connecting wires,the circuit will not work ...
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1answer
18 views

What does the phase discriminator portion of the Costas Receiver do mathematically?

What does the phase discriminator portion of the Costas Receiver do mathematically? The output of the $I$-channel is $ \frac{1}{2}A_C \cos \phi \, m(t) $. Which means for small deviation of phase $ \...
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1answer
35 views

Why is a specific voltage limit needed to light a bulb in an electric circuit

The battery provides a potential difference between its terminals that allow acceleration of the electrons in the circuit, i.e the potential energy gets converted to kinetic energy, these electrons ...
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0answers
22 views

capacitance of cube skeleton

A cube of 12 capacitors is very common problem. find capaciance accross edges we get 12c/7. But lets say we have 8 more capacitors involved now. that is we have capacitors at all sides of cube and ...
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0answers
15 views

Question on the magnetic flux inducing current in the secondary winding of a transformer

In transformers, does all of the magnetic flux change make a current in the secondary winding? Or just a part of it, and other part of it will cause self induction?
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1answer
41 views

A voltmeter is connected in parallel across the load. Why? [duplicate]

Voltmeter is connected in parallel across the load. Why?
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Intuition behind swapping the known and unknown resistance in a slide wire meter bridge

Today I was learning about wheatstones and balanced meter bridges. But while learning about the sources of error while working with the meter bridge (measuring unknown resistance), I couldn't ...
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1answer
67 views

How do I connect a four way key in a potentiometer?

How do I connect (which wire to which terminal) a four way key to a Potentiometer to compare the EMF of two cells. Circuit diagram and a four wayway key is shown in the pictures.
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1answer
34 views

Which law is true at the transformator?

According to Faradays law The changing flux will generate voltage in the secondary winding/circuit, so if the N2 = 2*N1, then the U2 =2*U1, and according to conservation of energy in that case I1 = 2*...
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2answers
65 views

Sonomotors, Sion: Can this electric car really charge up to 30km only from its solar cells? [closed]

Maybe you have heard about Sonomotors and its futuristic electric car, the Sion. If not, here is the link to its website: https://sonomotors.com/ Anyway, the manufacturer claims that this car can ...
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3answers
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How to determine which bulb will be the brightest in the series and parallel connection?

I stumbled upon these sentences while studying and this seems to be horribly confusing. resistance is proportional to the inverse of the power of the bulb in series connection and so the bulb with ...
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2answers
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How do voltmeters measure work done over a component?

In my physics class, we were shown the picture below to measure the current and potential difference through a component. We were told that the resistance of the ammeter is as low as possible, and the ...
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1answer
50 views

How is the current density derived?

I would like to know how the formula $J= \sigma E$ Our teacher said that all of the books never really explained how they found the question, so I assumed someone here knows the equation.
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How step-up transformers help in transmission of electrical energy over long distances?

i have read just read this blog: http://www.blueraja.com/blog/194/do-transformers-obey-ohms-law below blockquotes is taken from the blog above: We connect a 1 volt AC generator to a 1 ohm ...
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4answers
63 views

How can there will be current in purely inductive circuit? [closed]

In a purely inductive circiut there are two emf's one is applied and other is induced applied emf and induced emf are equal and opposite, then how can there will be current in a purely inductive ...
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2answers
56 views

What are the Possible Dangers of an Overheating Household Wire? [closed]

Can anyone tell me any possible dangers/risks that could happen if a wire overheats even if it's insulated properly?
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1answer
33 views

If voltage across a capacitor GROWS till maximum in finite time then, is it possible that the capacitor also reaches maximum charge in finite time?

When a dc-voltage V is applied to a capacitor C, the charge on it takes infinite time to reach maximum value ...
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Kirchhoff's loop law: why doesnt the battery affect the second loop at all?

So the explanation my textbook offers is that the power generated by the main battery is VI, which is equal to the sum of power dissipated in each resistor. hence, VI = RI^2 and V = IR. However, the ...
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3answers
67 views

General Definition of Potential in Circuits with Time-dependent Fields?

Electric potential is a very common observable to measure (especially in electro-engineering fields). It is measured using a multimeter, and thought of as the energy per charge that one charged ...
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1answer
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Relation between voltage and EMF of a battery [closed]

In the image :- R is resistance in the circuit r is the internal resistance of the battery E is the EMF of the battery V is the voltage across the resistor R Arrows show the direction of current. ...
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6answers
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Does the resistance of the voltmeter affect the behavior of this circuit?

I have this setup. It consists of a battery of no internal resistance with voltage $V$ and a resistor with resistance $R$. It also consists of a voltmeter of some (not so large) resistance as good ...
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2answers
49 views

Power in a simple electrical circuit [closed]

In this picture, as we know power due to heating of the resistance is $V^2/R$ . Now, if we add a parallel resistance to the circuit, the power dissipated through this resistor is also $V^2/R$ ...
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1answer
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Dissipation of energy in inductors

Please explain the dissipation of energy in a circuit containing a resistance and inductor after the switched in the circuit is opened.I mean how do you explain that the energy that is across inductor ...