# Questions tagged [electric-circuits]

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

2,473 questions
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### Why RMS for average voltage in AC current? [duplicate]

We write rms formula as $$v_{rms}=\sqrt\frac{\int_a^b[f(x)]^2dx}{|b-a|}$$ I know if we take arithmetic mean average voltage will be 0. So we want all voltage values to be positive. Why don't we do ...
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### 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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### Discrepancy in capacitor

Let a capacitor be connected to a battery in a circuit. The battery does work worth $CV^2$ but the capacitor stores only half that amount... We say the other half went away as heat, but how do we ...
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### What happens if you connect a wire to the anode of a battery, but not the cathode?

My understanding is that the anode of a battery is positive while the cathode is negative. If you connect a wire between the cathode and the anode, then the electrons in the cathode want to flow to ...
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### Intuitively, why does putting capacitors in series decrease the equivalent capacitance?

Can someone please explain, intuitively (without any formula, I understand the formulas), why the equivalent capacitance of capacitors in series is less than the any individual capacitor's capacitance?...
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### Problem while constructing langmuir probe

I am working on DC glow discharges and want to construct a langmuir probe. Circuit I am using is as shown in the picture Also, I am applying ~1KV across cathode and anode. Problem I am facing is that ...
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### Why inductor voltage at $t=0$ is equal to source voltage?

I am sorry to ask this elementary, fundamental and most repeatedly asked but i have some doubts that were not cleared during my undergrad days. I will try to present my doubts in following points. 1 ...
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### How to derive the $\Delta$-$Y$ formula for capacitors?

So, I've found a youtube video that first derives the formula for the resistors and then says the capacitance is the resistance^(-1). I was wondering if that would be the right approach.
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### Is Ohm's Law Valid for AC Circuits?

Specifically, let us talk about a circuit containing only an AC source and a capacitor. In this case, the current is 0 at the instant the source voltage is maximum. Same is the case when the circuit ...
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### Will high voltage but low current glow a bulb?

Suppose I increase the voltage supplied to a building from a constant power source substantially by putting a transformer. Doing this would reduce the current substantially as well. So will the ...
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### How do surfaces charges accumulate?

When a voltage source is applied across an ideal wire, do the push of electric field of battery source causes the accumulation of charges on the surface of wire or the capacitance of wire causes it? ...
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### Why doesn't a conductor between two wires affect the current wires?

When an aluminum plate is placed between two wires (lying parallel to each other), it doesn't change the repelling nor attracting force between the wires when a current is passing through them. But ...
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### Magnetic Field and Electric Feild Confused

So I'm still confused on how a change in magnetic field could induce an electric field and vise versa. When I got introduced to the idea of the induced electric field we looked at a circuit with one ...
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### Does the potential difference between two points remain the same if there spatial location is changed?

I was working through this particular homework problem. Where I am required to find out the current flowing through the resistor A (4 ohms). First of all I saw that the 2 resistors were in parallel ...
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### The rail gun experiment revisited

A metal rod is closing a horizontal electric circuit as shown here. We apply a vertical magnetic induction $B$ as shown. The magnetic (Laplace) force on the rod is $F=I\ell B$ to the right. If $F$ is ...
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### Five resistors' combined resistance [closed]

There are 5 resistors. Can you help me to find total resistance? Sorry for image quality.
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### Equivalency of $Q$ Factor Definitions

The Q factor is defined (seemingly) as $$Q=2\pi\frac{\mathrm{energy \, \, stored}}{\mathrm{energy \, \,dissipated \, \, per \, \, cycle}}$$ however on Wikipedia is says that the Q factor can be ...
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### Principle of potentiometer

I could not understand why the emf of the main cell (labelled E) in the circuit (can be a battery eliminator) should be greater than the emf of the cells (E1 and E2) used in the secondary circuit. ...
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### How cell drives electrons to flow in a metal wire?

This was my approach using some facts I'd known- At cathode and anode of a cell reactions take place making positive terminal positively charged and negative terminal negatively charged I.e. there are ...
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### Why do electrons accumulate on the surface of a wire (along its length) when a voltage source is applied across the wire cross section?

When I was going through how electric fields are transmitted long distances through a wire, I read that there was accumulation of charges along the surface of the conductor to drive the fields to long ...
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### Why the resistivity of differnet materials is different? [closed]

On what factors it depend? I have been wondering why it does not depend on the density of a substance. If atoms would be closely held then the flowing charges would have to face more obstruction.
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### How can i calculate the amount of current and voltage consumption for every turn of electromagnetic pulse generator? [closed]

For example if i use 240 voltage source for electromagnetic pulse coil with 100 turns around the core how could i know the amount of remnant voltage and ampere that come out from the wire at the end ...
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### Resistors equivalent using symmetry and equipotential line

I propose the following statement: In a circuit, while determining equivalent resistance across two points, if the circuit is symmetric wrt the line joining the two points , we may fold the circuit ...
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### RC circuit series and parallel [closed]

R and 2R are in parallel. 4R and 3R are in parallel. I dont know where to go after calculating the the parallel Rs. Do you become in series? If so, how? It is right after the switch is closed. So ...
159 views

### Why doesn't the electric potential constantly decrease in a circuit as the current moves from the positive to the negative terminal?

Why doesn't the electric potential constantly decrease in a circuit as the current moves from the positive to the negative terminal? Details and Assumptions: 1. The wires show no resistance.
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### Electric potential in circuits

From what I understand from my notes, an e.m.f or electromotive force provided by a battery is the electrical energy per unit charge converted from other forms of energy required to drive a unit ...
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### Express Laplace transform of voltage across a capacitor in terms of charge

In Charge Tunneling Rates in Ultrasmall Junctions section 2.1, the authors consider the problem of charge relaxation in a simple circuit shown in Figure A. The implicitly use an assumption made about ...
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### Trouble with Kirchoffs Law and EMF

So I'm having some trouble using Kirchhoff's second law . For example suppose I have a battery that supplies a constant emf $\epsilon_0$ and is connected to a resistance R and inductance L. I don't ...
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### What am I doing wrong with this Wheatstone Bridge? [migrated]

Experienced experimentalists, be aware that this is probably going to sound like a stupid question: I am having a LOT of trouble predicting the output of this Wheatstone bridge circuit. I am trying ...
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### Frequency of the Primary Circuit in a Spark Gap Tesla Coil

In a simple spark gap tesla coil, how does the oscillating current in the primary circuit interact with the supply voltage/current? If the power supply comes from a transformer hooked up to the ac ...
120 views

### How LC oscillator is used for generating signals?

I have been trying to understand some practical applications of LC oscialltors and I dont seem to find much information available on net. One consistent application that I see is "LC circuits are used ...
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### Joule's heating effect

Can we derive joule heating effect or heating of current using energy conservation for electrons when current is varying with time ?Like using concept of drift velocity,potential diffrence across ...
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### Can EMF be lesser than terminal potential difference?

Can terminal potential difference be greater than EMF? If so, how? Upto my knowledge and my research, during charging it can happen but the question remains same: how it happens. What is the basic ...
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### General idea behind simplifying cube resistors

I don't know if "cube resistors" is the right way of putting it, but I am wondering if somebody could walk me through the general procedure for solving problems in which you are asked to find the ...
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### Telling if Capacitors are in Parallel or Series

So C1 and C2 are in series. But if each one is placed in red boxes, they are in parallel? It's confusing going jumping between current, capacitors, and resistance. For me it's kinda confusing ...
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### Shot noise and single photon detection

I am looking into the noise considerations of a single photon detector, specifically an avalanche detector. I am wondering if it makes sense to think about shot noise when considering a single photon. ...
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### Does charging any electrical device in exterme temparature affect the current flow?

Recently in an Electric vehicle(EV) charging station, the charging time to charge a particular vehicle was 1 Hour (18V capacity of battery), but now in temperatures beyond 40 Degree Celsius, it is ...
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### Do the electrons arrive at the anode with some kinetic energy? Where does it go?

I'm studying electronics and circuits. I'm trying to understand how electrons behave as they move in a circuit, but there's something that still bothers me. Electrons have some potential energy (the ...
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### AC frequency and Conductivity measurement

Hello I'm currently writing my Bachelor thesis and work with a probe which is supposed to measure the electrical conductance with an alternating current. Its composed of two electrodes made 5 mm long ...
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### Ideal/Non ideal Voltmeter across a battery with no current flowing

If I consider a voltmeter and connect it across a battery , which is in such a circuit , that no current is flowing in that branch (Before Voltmeter is connected), will the voltmeter, show the EMF of ...
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### Induced Currents in Circuits

I was given the following question:- The plane figures shown are located in a uniform magnetic field directed away from the reader and diminishing. The direction of current induced in the loops is ...
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### Internal resistance and Instantaneous current?

Okay, this would probably seem a pretty basic doubt but I can't understand this thing. I know that when the current is not flowing in the battery the voltage across the terminals is the emf of the ...
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### signal propagates in unequal length (or bended) transmission line

Suppose I have a square wave signal generated from a signal generator and its outputs are connected to the two terminals of a paired PCB traces (left side of the picture below). The other end of the ...
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### Why don't we consider the electrical potential being converted into kinetic energy when working with circuits?

Assume we are working with a postive test charge : In an electrochemical cell work is done by the chemical reactions to move a positive test charge from the negative terminal to the positive ...
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### Determining current in a branch having no resistor

In context to the diagram below , it is quite easy to find the current flowing through section AD , which turns out to be 2A , however , I cannot determine the current in any other branches with ...
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### Why does this derivation/proof of KVL from KCL and Tellegens theorem hold?

I have come across a strange derivation of Kirchhoff's voltage law. You assume that Tellegen's theorem and Kirchhoff's current law both hold. (Bold letters signify a vector.) The proof: Let L be an ...