Tagged Questions

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

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Parallel combination of cells [on hold]

In this circuit suppose that $E_1 >E_2$. This means that the positive terminal of $E_1$ will have a greater potential than the positive terminal of $E_2$. Then current should flow from the ...
27 views

How to create something that can emits negative charge [on hold]

If I find an object or a matter that can emit positive charge, then is it possible to create or get something that will emit negative charge as well?
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Charge of electron in AC/DC circuit

If electrons in a DC circuit going through a metal wire carry only negative charge from negative to positive, then in a AC circuit through a wire does a electron carry both a negative charge and ...
932 views

Why is current the same in a series circuit?

So I am a 10th grade student and my teacher told me that the current is the same at every point in a series circuit. It does split up in parallel circuit but it then recombines and the current flowing ...
27 views

Question regarding Kirchoff's loop rule

My problem is that there are n cells connected in parallel which are connected to an external resistor. Now can we use Kirchoff's loop rule to evaluate the current through the resistor by considering ...
615 views

Why is the resistance in a parallel circuit smaller than the resistance in a series circuit?

So I was told in the physics class that the resistance in a parallel circuit is smaller than the resistance in a series circuit. Why does that happen? Is this statement also true for circuits which ...
12 views

frequency passage inside AC ciruit

I've been checking YouTube about AC circuit lesson and been hearing about inductor passing low frequency and capacitor passing high frequency from alternating current and what does that mean by ...
21 views

Range of voltmeter [closed]

I have understood how the range of an ammeter cannot be decreased. But I don't seem to understand how the range of a voltmeter can be decreased. Pls help.
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Same current flowing [closed]

In the following circuit how can we say that the current flowing through both the $4\Omega$ would be same . I know it would be same if in middle the $\frac{2}{3}\Omega$ is not there but here it is ...
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Infinite staircase where each step is a 1 ohm resistor [closed]

There is an infinite staircase where each step is a 1 ohm resistor. How do you calculate the equivalent resistance between any of the two points on the staircase?
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Circuit with voltage source, resistance and current source

Suppose I have a (closed) circuit with a voltage source $V$, a resistance $R$ and a current source $I$ (in this order). Is it true that the voltage across the current source is $V-RI$ ?
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Is it true that in a superconductor the current will always flow without a any electric source? [closed]

It came to my mind that when a superconductor is taken and a wire is joined to it to make it a complete circuit, the current is flowing through it. Now, I am removing the battery and joining the two ...
65 views

Electrical equivalent of inverted pendulum

Background I am working on a summer project to design labs for undergraduate students. One of the topics is feedback and there is already quite a lot of stuff about passive feedback, so we might add ...
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Relaxation Time in RC Circuits with a Metal Conductor

In section 4.8, Variable Currents and Capacitors, of Purcell and Morin's Electricity in Magnetism, the following is discussed: For a metal with resistivity typically $10^{−7}$ ohm-meter, the time ...
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Energy dissipation in current flow

In section 4.8, Energy dissipation in current flow, of Purcell and Morin's Electricity in Magnetism, the expression for the power expended by a resistor is derived. The sections includes the following ...
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Can the Hall effect drive a current?

In the Hall Effect current is passed through a wide strip of metal in a perpendicular magnetic field. Since (some of) the negative charges in the metal move but the positive ones stay put, the ...
58 views

Equivalent Resistance between 2 points

Actually , I'm having trouble in solving for the net resistance of the below network of resistors. Can anyone help me finding the equivalent resistance between points a & b. My answer is $2/3r$...
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Determining if two resistors are in series or in parallel. [duplicate]

I know that this is a rather trivial question, but I've been having issues developing a problem-solving strategy for figuring out whether resistors are in parallel or in series. The Specific problem ...
42 views

Why would a series of cells not be suitable for a car battery? [closed]

A car battery needs to supply a current of $200A$ to turn over the starter motor. Explain why a battery made of a series of cells would not be suitable for a car battery. My thinking: I'm thinking ...
104 views

What is the voltage drop across a wire [closed]

If we attach a resistor in series, most diagrams only consider the voltage drop across the resistors. What happens when we remove all of the resistors? Why does the voltage drop across the wire become ...
42 views

Electric potential in a wire

I am slightly confused on the physics of direct electric circuits. Here is what I have been taught: Batteries (sources of emf) provide a constant potential difference between its terminals; ...
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Which AC bridge circuits are oscillators? [migrated]

There are different types of AC bridge circuits like the Wheatstone bridge, Maxwell, Hay, Shering and Wien. I need to know which ones are oscillators but I still don't get the main reason why the ...
63 views

Differential equation in RL-circuit

I am self-studying electromagnetism right now (by reading University Physics 13th edition) and for some reason I always want to understand things in a crystalclear way and in depth. Now look at this ...
80 views

Work done by the battery in series with capacitor with changing dielectric

If we have a battery with voltage $V$ connected in series with a parallel-plate capacitor of capacitance $C$ with dielectric $\epsilon$,and then we pull the dielectric out, the infinitesimal work done ...
25 views

Resistance increase with length because of more scattering?

I am referring to one of the answers to this old question. I can't add comment to it because I don't have enough reputation. So here I rephrase the question: does resistance increase with length ...
20 views

By which equivalent circuit (RC serie or RL serie) can I substitute the following circuit?

I was trying to solve the following question: "Assuming that 𝐑 = 𝟏𝐤𝛀, 𝐂 = 𝟏𝛍𝐅, 𝐋𝟏 = 𝟔𝐦𝐇, 𝐋𝟐 = 𝟑𝐦𝐇, 𝐞 𝛚 = 𝟏𝟎𝟒 rad/s, tell if the circuit can be substituted by an equivalent RC ...
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Even when the drift velocity of the electrons is very small, how is current in the circuit established immediately?

So I have this question in my textbook and Ive also got it in my test. Ive written a wrong answer. My friend wrote the drift velocities of each particle add up and he got full marks. Is it right? Can ...
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Earthing, neutral and Earth's conductivity

Ok so this is gonna be a lot of mini-questions. What exactly is the neutral wire? How does earth conduct electricity for a live AC mains even though its just dirt and stones (it should be an ...
51 views

What happens when an AC source is connected to a capacitor and a LED?

When a DC source is connected to a capacitor and a LED, and the voltage is removed when capacitor is charged, the capacitor supplies current to it for some time. What happens if this DC source is ...
36 views

Laser as an optical oscillator

How can Laser can be compared to a positive feedback amplifier? Does the two conditions for oscillator holds good for lasers too.
25 views

holes in an electronic circuit [closed]

Many times, by looking at electronics circuits I noticed that they have like small holes printed in yhem. The question I want to ask is, what s the purpose of these holes?
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Resistor in series

We know that when a resistor is connected in series , the current flowing through that resistor will be constant.But how do we use a resistor to limit the current flowing through a circuit ,when ...
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Elementary derivation of $P = UI$ starting from the definition of voltage as work done per unit charge

Consider the following elementary derivation of the formula $P = VI$ for Joule heating of a resistor $R$ for the dissipated power $P$ where the voltage over the resistor is $V$ and the current $I$. ...
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Proof of Kirchoff's second law [closed]

There are 2 approaches I have stumbled to prove Kirchhoff's second law: Derive it from the conservation of energy. You can derive that from "integral of E*ds = 0". Can you show me a full or at ...
54 views

I'm learning electromagnetism from Purcell's book. He say that if we have the following circuit: $$-\frac QC + RI = \mathcal E_0\cos\omega t~,\quad I = -\frac{\mathrm dQ}{\mathrm dt}$$ The ...
38 views

Possible reasons of electrocution in a good earthed appliance during sudden power off [closed]

I was working in a industry. When I was using a machine, I felt slight electrical shock at the exact moment when the power supply went off. The machine is properly earthed. In spite of that I got ...
16 views

What's the back EMF on a spherical conductor suddenly surrounded by a negatively charged shell?

Suppose one has a spherical conductor of radius r. Suppose it is suddenly surrounded by a negatively charged shell. The conductor will rush to balance out the voltage. However, this changing current ...
19 views

When happens to the current during reversed biased?

The main working function of a half wave rectifier is to convert AC current to DC. My problem is to understand during the negative cycle. The above picture is time versus current. We can see easily ...
53 views

Why Thevenin's theorem is being violated?

in the given picture we need to find the current flowing through the 3 ohm resistor. Applying KVL we can find the current as 4 amps but if we thevenise the circuit at terminal a-b then the current we ...
39 views

Behavior of coil and resistance in DC circuit [closed]

I have a simple circuit of a coil parallel to a resistance and then in series with another resistance. I wanted to understand the behavior of this circuit so I ran a simulation, and what I noticed is ...
135 views

Is resistance proportional to resistivity: $R=\textrm{const}\cdot\rho\;?$

Suppose we have a resistor in a strange shape, filled with a medium of resistivity $\rho$, assuming only Maxwell's equations apply, is it true that resistance $R$ is proportional to $\rho$, even for ...
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Is peak voltage or peak current kept constant when we change resistance in an AC circuit?

I found online that Ohm's law still applies to an AC circuit and that $V_{peak} = RI_{peak}$. However, I can't seem to find anywhere weather an AC source will : Act as a voltage source and keep its ...
66 views

Circuit theory paradox - Unexpected results [closed]

I recently studied capacitors and found out that there is something called 'ideal circuit paradox'. Searching Google I found that one can cannot find the potential difference between two points in a ...
56 views

Why is there only a drop in potential energy when charges flow through a resistor?

First, I read that if you move a charge (say a positive charge) against an electric field, its electric potential energy increases because you're doing work to move the charge to that position. I also ...
43 views

Different voltage drops depending on the path

I was working through a problem in electromagnetic induction when I discovered that I have a fundamental ignorance of some sort that is puzzling me. Consider a circular wire, at rest, perpendicular ...
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Is it possible to measure the resistivity of something using A.C. Current and a capacitor?

I've read that A.C. current "passes" through a capacitor. Is it possible to use this and measure the resistivity of the medium between the plates? Any sources or links would be appreciated.
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Armature of electric bell [closed]

I want to know that why is the armature of the electric bell made up of soft iron ? I googled this out and everywhere it was written that it is because of its propert to aquire electromagnetism but I ...