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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 to use energy conservation in following case [duplicate]

A capacitor of capacitance C is intially uncharged is connected with a battery of emf ε.Find the heat dissipated in the circuit during charging?How can we apply energy conservation although there are ...
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2answers
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Does current flow in the wire when only one terminal of the battery is earthed?

Let me specify beforehand that this question has been asked previously but I haven't been able to satisfy my curiosity.I know a battery maintains a potential difference between it's terminals , let's ...
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1answer
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Work done in moving a charge in circuit?

Why is the work done in moving a charge from one point to another in a circuit through any path the same even though heat and other losses are there?
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I inserted my DC toy motor into and AC power outlet. Sparking happened and the motor isn't working anymore. What exactly happened?

What took place inside the motor and why isn't it working anymore? I familiar with basic electricity and circuits, but can somebody explain it in easy language.
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Finding the voltage across an inductor when opening the switch [closed]

Well, I've the following circuit: In the circuit I want to find the voltage $\text{V}_{\text{Y}_1}\left(t\right)$ as a function of time, after I open the switch (this switch was closed 'forever' ...
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1answer
25 views

Transient state analysis of RL circuit

A circuit consists of an ideal battery an ideal inductor and zero resistance. The value of inductance is $4$H and the battery has an emf of $2$V. There is fuse in the circuit which breaks after when ...
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1answer
26 views

RC circuit: is order of resistance and capacitor important?

in a RC circuit is order of resistance and capacitor important? Typically there is the battery then the capacitor then the resistance, but is it ok if I draw with the battery then the resistance and ...
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2answers
56 views

Work done by battery?

Why the work done by a battery is Q*V where V is emf of battery and Q is charge that is made to flow in circuit?please explain detail? explain and write the formulas
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48 views

Impedance of an LCR circuit

So I am trying to understand how to find the impedance of the parallel LC component of this filter circuit. I am given that the transfer function $\mathbf{T}_C = \dfrac{\mathbf{V}_{out}}{\mathbf{V}_{...
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Origin of Josephson voltage equation?

i cant find a satisfying explanation, and I cant figure it out myself, a derivation for the josephson equation: $$U(t)=\frac{\hbar}{2e}\frac{d\phi}{dt}$$ where $U(t)$ is the voltage, and $\phi$ is the ...
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1answer
29 views

Overestimation Problem [duplicate]

I had asked this problem earlier but I was too vague in how I asked it so I'm making a new post to be more specific. Problem: Say we have a series circuit with an ammeter, a cell with internal ...
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1answer
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How can the Neutral wire be 0V if its AC? [duplicate]

So I understand Alternating current like a battery, in which the Poles are constantly changed out, so the circuit stays completed, but the electrons change directions. But how can then in an AC plug ...
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1answer
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Inductors in parallel circuits

I recently encountered this problem dealing with inductors, similar to the diagram below. The switch is closed for a long period of time. I know that eventually the inductor and act like a short, ...
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4answers
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Why is there no current between two capacitors connected in series?

I want to ask a question about the figure below. Why the current does not flow from $-Q$ term to $+Q$ term or from a to b since there is a voltage?
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1answer
26 views

When the external resistor increases in temperature, why is the calculated value for internal resistance higher?

Say we had a circuit with a cell (with internal resistance)and an external resistor of 10 ohms as shown: The 10 ohm resistor then increases in temperature, leading to an increase in resistance in ...
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5answers
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Why does the potential difference across a type of parallel circuit not act like a potential divider? [closed]

Image credit (Q3) In this attached circuit, when $R_1=0\Omega$, I am failing to understand how the two cells affect the potential difference across the central resistor R3. I understand that ...
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5answers
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Isn't Kirchhoff's junction law a violation of conservation of charge?

As a beginner of classical electrodynamics I am quite confused in understanding Kirchhoff's junction law or it may be the reason that I misunderstood the law of conservation of charge.Please correct ...
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2answers
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Does Kirchhoff's rule break down as it applies to capacitors

A homework problem asked me to find the voltage across a series of capacitors after they came to equilibrium. Essentially a capacitor C1 with a capacitance of 6.0 F is charged until the potential ...
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3answers
70 views

Voltmeter reads zero with two same batteries connected in series [closed]

this is an a level physics question, can someone here please explain why voltmeter reads zero and how changing resistance of variable resistor effects voltmeter reading. The main concept i want to ...
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5answers
84 views

If current through a resistor is zero, does the circuit break?

I'm really confused. I'm studying about how capacitors are charged, and I learnt that there's a resistor attached in series with the capacitor when it is being charged. When the capacitor is fully ...
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0answers
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Photoresistor in Parallel [closed]

I am currently building a photoresistor from a kit that I bought a few months ago. I had a few questions when I was building this circuit: What happens when you wire the photoresistor in parallel ...
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3answers
64 views

Charging capacitor in an incomplete circuit [closed]

I have 2 confused questions regarding the below circuit. please help me out How will the capacitor even charge in the following scenario when the right side of the capacitor is not connected to ...
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1answer
47 views

Evaporating tungsten wire

Consider an incandescent bulb having a thin filament of tungsten that is heated to high temperature by passing an electric current. The hot filament emits black-body radiation. The filament is ...
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Why does the base-emitter voltage in NPN transistor become constant

The setup above shows the experiment that I have been working with. During the experiment, the current $i_c$ and the voltage $V_{be}$ were measured for increasing $V_{in}$. At some point, the current ...
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1answer
46 views

Neglecting capacitor from circuit

Take a look at this circuit : This question is answered in $Serway$ $7th$ ,And the book neglected 8 Farad capacitor because the voltage between $c$ and $d$ is zero. My questions is : $1.$Should not ...
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1answer
26 views

How can we analyze electronic capacitors in series? [closed]

Two capacitors are in series, such as in this circuit diagram: When doing a circuit analysis, how can we describe the voltages and charges across the two capacitors?
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3answers
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Current Divider rule

If you have two resistors $R_{A},R_{B}$ connected in parallel with a battery, you can find the current that flows through one resistor ex.$R_{A}$ using the current divider rule: $$I_{A}=\frac{V_{T}}{...
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Estimating the effect of inductors in an RL circuit

I'm trying to understand how an inductor works in an RL circuit. When I use an air core inductor, my estimation is fairly accurate to the test circuit but as soon as I use an inductor with a core, the ...
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1answer
102 views

I got this formula but can anyone prove it [closed]

Yesterday while doing some questions, I came across a formula that if a wire with uniform resistance R is made into n sided regular polygon then the net resistance between any two corners with $x-1$ ...
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2answers
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Why does electrical resistivity have units of $\Omega \cdot \mathrm{m}$ rather than $\Omega \cdot \mathrm{m}^3 ?$

Electrical resistivity has units of $\Omega \cdot \mathrm{m} .$ However, since resistivity can be described as the resistance of a unit cube, shouldn't the units therefore be $\Omega \cdot \mathrm{m}^...
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3answers
115 views

How does resistance affect the voltage drop? [closed]

There is a series curcuit and there are 5 resistors in it which are the light bulbs. I know that current is directly proportional to the voltage and inversely proportional to the resistance. Can ...
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1answer
42 views

Redrawing circuit rules

Take a look at this circuit: Is it allowable to redraw the circuit like this ? Can I move cd wire until it merge with b junction ? Can I move e point like what I did in the figure ?If yes why this ...
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0answers
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Stochastic version of the Kirchoff circuit law

I assume this question could be written in a non-technical jargon, but I will try to be as simple as possible. The Kirchoff circuits law assert that the sum of inward and outward currents at a node ...
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1answer
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Magnetic Circuits: Why is magnetic Flux constant through one loop of a magnetic Circuit?

Wikipedia states that for a magnetic circuit, the magnetic flux throughout the path of the circuit is constant. If I understand right, this means that \begin{align} \Phi_1 = \Phi_2 = \Phi_3 = \Phi_4 =...
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2answers
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Parallel circuits at home

My textbook states that if you have a light bulb turned on and you connected a hair dryer with it in parallel, then the brightness of the light bulb will decrease. The reason my textbook provided, ...
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2answers
74 views

Why I can't find a value for the resistivity of plastic? [closed]

I'm working to a relation about resistence of various materials. I haven't found a table of resistivity wich includes Plastic. Is searching plastic too general? Does a table in which there is at least ...
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How is energy transferred to a resistor in an electric circuit?

I'd really appreciate some help understanding this. I've always thought that in a circuit, some source of potential (such as a battery) accelerates the electrons in the circuit, and that collisions ...
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1answer
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How to solve these kind of electric circuit? [duplicate]

This question from Physics For Scientists And Engineers 7th page 746. After redrawing , Actually I cant see any two clear capacitors that we can be combined , First we cant combine $C$1 with $C$2 ...
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1answer
23 views

How is current affected by a charging capacitor in parallel to a resistor?

Imagine a circuit with a battery followed by a lightbulb and an uncharged capacitor in parallel. Next to it is an open switch. When I close the switch completing the circuit, does the brightness of ...
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2answers
60 views

Current in the inductor at $t=0$

$L_1 = 5H, L_2=0.2H, M=0.5H, R_0=10 Ω$, and $i_g=e^{-10t}-10 A$. I need to find $i_2$. I've started with DE $$i_2R_0+L_2(di_2/dt)+M(di_g/dt)=0$$ and solved it for $i_2$, so $$i_2=0.625e^{-10t}+Ce^{-...
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Regarding induced magnetic field due to changing electric field

I am trying to solve this question: My approach was to first notice that the electric field is decreasing, therefore the change in electric field is to the left. If I point my thumb in the direction ...
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0answers
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Effects generated from a supercapacitor placed in a time varying external magnetic field?

The diagram above, showcases the simple outlook of a supercapacitor's interior and combining it with a full circuit loop. If an exterior magnetic field is introduced in all the operating states of a ...
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Effects of opposing fields in coupled inductor

This is a duplicate question that I already made in the electrical engineering part of stack exchange. As I`m asking for the physics behind the effect I thought it might be worth to ask also here. ...
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2answers
37 views

What is the Electron Flow in a wire with 2 power sources 180 out of phase?

If you took two independent power supplies and set them to a sine with each power 180 degrees out of phase. The powers supplies will share a common line and the load will be equal_____________? Do ...
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3answers
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When high voltage leads to low current in power transmission system how its not applicable for household voltages?

When high voltage leads to low current in power transmission system using transformers,how increase in voltage in household circuits from 220 volts makes the current increase damaging the appliances, ...
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2answers
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Parasitic capacitance in real resistors

Typically, I'd assume (A) is only a justifiable answer when the two metal end caps have essentially infinite area, or when the spacing between end caps is far smaller than their respective areas, in ...
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2answers
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Power in Series and Parallel circuits

My textbooks states that the brightness of a light bulb that is connected in a circuit is determined by its power. That is, a light bulb connected in series would be brighter if it has a higher ...
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Increasing Capacitance of a capacitor at constant voltage and frequency in a resonant circuit

A question in my textbook; If a RLC circuit is in resonance case, show what will happen to the hot wire ammeter's reading at increasing the capacitance of the capacitor at constant potential ...
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modelling electric field of dielectric in a capacitor

I have a question about how Gauss's law is used to calculate the induced charge on a plate of a capacitor. A text that I've been reading (Halliday, Resnick, and Walker) explain that a dielectric in a ...
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2answers
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What should be the independent variable in a resistance experiment?

I was asked a question by a student today and I have been pondering about it for a while now. In an experiment to measure resistance of a conductor, should we vary voltage across the conductor and ...