Questions tagged [electric-circuits]

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

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Electrical systems with multiple connections to earth - is earth modelled as one region of equal potential here?

In the picture we can see a realization of a TT-System, an electrical system with multiple connections to earth at different localiations. I allready know (from this question) that the coulomb-...
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1answer
28 views

Initial Current of Inductor?

I know that a capacitor can be charged up to store energy, then if we disconnect the capacitor from the source and hook it up to a light bulb, it will light up since the energy stored is used to power ...
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1answer
55 views

Resistance and temperature relationship

When the temperature changes from $\theta_1$ to $\theta_2$, having $\alpha$, and the amount of resistance ($R_1$) in the previous temperature ($\theta_1$), we can calculate $R_2$, the amount of ...
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1answer
65 views

Calculating electrical resistivity of a material

If I plan to measure the resistivity of a high resistivity material, would it not make sense to alter the geometry of the sensor to make A/l as small as possible and reduce the voltage to get a low ...
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24 views

Question about amp-hour and batteries in series

I am a little confused about this wiring batteries in series and parallel and the effect of this on total time that these batteries can last(I suppose this is called amp-hour, correct me if I'm wrong) ...
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2answers
60 views

Why does current always go to the resistance which is lower? [duplicate]

Why does current chose the easy way? Is there a proper mathematical formula about why current tends to go over a resistance which is smaller?
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2answers
79 views

Why does current remain same in a series circuit?

Current is the rate of flow of charges with time. When passing through each resistance in a series circuit, charges lose energy and "slow" down due to collisions with atoms (metal cations). When time ...
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0answers
44 views

Is high frequency alternating current capable of rotating induction motor? [closed]

I have 100khz AC power that can light up a bulb, can I use this to run small induction motor? I want the Lorentz force to push rotor coil, I know that motor would not rotate at 100000hz rate but it ...
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2answers
36 views

Why Does a Bulb’s Individual Resistance Increase When Wired in Parallel?

When I wire three bulbs in a series, the resistance of each bulb is around three ohms (using R=V/I). If I rewire the same bulbs into a parallel circuit, the resistance of each bulb is slightly over ...
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0answers
14 views

Current through the secondary of a transformer

If I know the wattage of the primary of a transformer, and the input voltage, how do I calculate the current flowing through the secondary, if a load of some resistance is placed across the secondary?
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1answer
54 views

How to calculate total power generated?

I have a circuit with a piezoelectric transducer which converts mechanical energy to electrical. The ceramic is connected to a 1 Megaohm resistor and a voltmeter which reads voltage. If I want to ...
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1answer
57 views

Are Electrons in a Circuit Subject to Newton's Third Law?

Consider a simple electrical circuit made up of a battery, an incandescent bulb, and wire. The battery and bulb are equal in mass and are on opposite sides of a circle made up by the wire. Lastly, the ...
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1answer
82 views

Different batteries in a parallel circuit

I have come across this question in my physics textbook. Two batteries are connected in parallel to a resistor (see the above image). The first battery generates $U1 = 9V$ of voltage and its internal ...
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0answers
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Free Electron-Bond Electron Interactions

I am reading an introductory textbook on electronics: Practical Electronics for Inventors by Paul Scherz and Simon Monk. In a section discussing the motion of electrons in circuits, the textbook ...
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1answer
26 views

How can be Bode diagram's phase value more than 90 degree or less than -90 degree?

It doesn't have any physical meaning, i think, because phasors doesn't have more than 90 degree or less than 90 degree value ? Also negative resistance doesn't exist.
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RMS values and phasor diagrams

In RL circuits (AC source) we use vectors to calculate the total voltage, I understand that we cannot add them algebraically because they do not exist at the same time as we are using rms values for ...
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2answers
37 views

Why do phasor derivations related to LCR circuits consider $V_c = I * X_c$ even if voltage and current are out of phase?

In a capacitor, the current leads by $\pi/2$. But even then derivations of of total voltage in LCR circuits using phasor diagrams assume that $V_{inst.} = I_{inst.} * X_c$ Where $V_{inst.}$ is the ...
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4answers
119 views

What remains the same: voltage, current or resistance? [closed]

A current 1 ampere passed through a conductor which resistance is 10 ohms, if the current become 2 amperes, then will the resistance of the conductor will remain 10 ohms, and if not, then what is the ...
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3answers
59 views

Voltages phasors in AC circuit

What does it actually mean to add voltages vectorially not algebraically in RL or RC circuits (AC source)? I know that the voltage drop across the inductor is maximum when the voltage drop through the ...
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3answers
85 views

RC circuit discharge while being connected to a battery?

I am facing a conceptual problem in analyzing the following situation which was part of a physics exam; A series RC circuit with $R = 200k \Omega$ and $C = 10 \mu F$ is connected to a 5V battery and ...
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8answers
1k views

Does Ohm's law $V = IR$ mean voltage causes current, or does it just say that voltage and current are related?

I have read that Ohm's law, $V=IR ,$ just means that $V$ is equivalent to $IR ,$ not that voltage is the cause of current. This is similar to the interpretation of Newton's second law, $\mathbf{F} = ...
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1answer
43 views

Inductors in AC circuits

Although I checked similar questions I still can't understand why the voltage across an inductor connected to an AC source is equal to $L\, dI/dt$ without the negative sign of Lenz's law, why isn't ...
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2answers
75 views

What happens when a battery is dead?

While studying circuits I am having a question that when we say a battery is dead.Do we mean that the voltage difference between the ends has become zero?If no,then what actually happens?
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3answers
38 views

Flow of charges inside a battery

I am having confusion about the flow of charges inside a battery which is connected to Circuit. Question is, do charges move from one end to another through the battery? If yes, how? Do they move ...
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10answers
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Is every open circuit a capacitor?

I think that even open-ended wires can let AC current flow through them, just with a low capacitance. I also think an antenna could be a capacitor and open ended. Am I thinking correctly?
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1answer
23 views

Electric fields and electric potentials in semiconductors

The zener diode is heavilier doped than a normal diode , that is why its depletion region is smaller than the delpetion region of a normal diode and that is why the electric field is very strong.Zener ...
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0answers
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Human vs. machine energy expenditures

I've read that a typical human-powered bicycle power generator generates around 100W. For the same amount of effort, the bike travels probably around 20k/h on a road. Does that mean it requires 100Wh ...
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0answers
24 views

Thermistor IV characterisitc

The circuit is a potential divider circuit with a NTC thermistor and fixed resistor. I know generally the IV characteristic for the thermistor however, I was given values of resistors voltage at given ...
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2answers
249 views

Energy dissipated across a resistor when charging a capacitor

I am a beginner in Physics and I am a little confused about RC circuits. I am working on a project in which I am measuring the power loss from a resistor when charging a capacitor in an R-C circuit. ...
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3answers
69 views

Can anyone tell me why the answer to this question is D? [closed]

I think the current will go through earth wire but my physics teacher told us the current will continue to flow through the circuit.
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0answers
15 views

Zener diode electric field working principle

Well I recently saw a video from khan academy about zener diodes.This video was suggested by another member of Stack Exchange Physics who I thank him very much . But I didnt understand some things:...
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3answers
70 views

Practical usage of batteries connected in parallel

Is there any practical usage in real devices for connecting batteries in parallel? Or is it more a theoretical construct? It seems to me that only batteries in series are used nowdays.
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0answers
23 views

Why do we change signs arbitrarily while calculating RC circuits formulas?

When I have to calculate the formulas regarding RC circuits, for example the process of charging a capacitor, there is a discrepancy between my calculations and those of all the books I can find. Let'...
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2answers
34 views

Empty and fresh battery in series

If you have 2 (e.g. 1.5V) batteries in series and one is dead/empty, what is the reason why a device is not working? Lack of voltage (1.5 + 0 is simply not enough for the device to operate)? From my ...
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2answers
55 views

Adding a capacitor in parallel improves power factor of an inductive circuit?

I know that to reduce power loss during transmission, we require a power factor as close to one as possible. This can be done by making $Z$ tend to $R$ which can be done by increasing $X_c$ such that ...
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1answer
67 views

Confusion with electric field in a capacitor circuit

I'm having a confusion involving a couple of laws for a capacitor: $C = \frac{Q}{V} \propto \frac{1}{d}$. The capacitance, the amount of charge the capacitor can hold for a certain voltage between ...
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1answer
43 views

What form does the electric field take in a voltage difference?

A laser of driving frequency $\omega$ emits a planar wave of the form $$\mathbf{E}(\mathbf{r},t) = Ae^{i(\mathbf{k} . \mathbf{r} - \omega t)}\hat{\mathbf{a}}$$ where $\mathbf{a}$ is the polarization ...
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2answers
43 views

Potential drop in slide wire (Potentiometer Experiment)

While doing the potentiometer experiment I was taught that the galvanometer will show opposite deflection on opposite ends of the slide wire. My questions are as follows: Why does this happen? In ...
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4answers
96 views

Electrons flow in Circuits

The electric field created by a battery through a section of wire in a series circuit is constant. This means that the force on each electron as it travels through the wire is constant. According to ...
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1answer
47 views

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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2answers
58 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
37 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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2answers
54 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
74 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
69 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
86 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
711 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
122 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
43 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
38 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 ...