# Tagged Questions

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

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### Inductor circuit

Consider a inductor circuit with an inductor connected to a DC battery and a switch. Initially the switch is open. At time $t=0$ the switch is closed. What will happen to the inductor just after the ...
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### Deriving the charge as a function of time in a discharging capacitor

There is obviously something I have not understood well. In Kirchoff's second law, we take the potential difference of batteries and capacitors with the sign that we traverse it. So, let's assume that ...
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### Thevenin's Theorem problem

I don't understand why $(c)$ is same with a circuit when removing power source at $(b)$. Isn't this same with this one? But how could this circuit could be $(c)$? . .
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### Impedance of transformers

What does mean by impedance reflecting? Why this phenomena occur? What does mean by Zl=zs to gain max power but power is constant in transformers?
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### DC motor, bulbs

What happens when you are getting low voltages ? Why fan becomes slow and bulb become dim ? Dye to low voltage or current? If power is V*I then due to low voltage current becomes low or not Many ...
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### Equivalence between voltage drop across capacitors and resistors?

In simulating a circuit, comprised of 2 capacitors of same size but different dielectrics, their capacitance ratio ${C1}/{C2} = \epsilon2/\epsilon1$. Problem is, in finite element programs, I am ...
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### Do light dimmers save energy and lower your electric bill? [closed]

Or do they just capture the incoming energy and turn it into heat at the unit and save you nothing?
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### AC Electricity as a Simple Harmonic Oscillator

Can the net motion of electrons in an AC circuit be considered an example of simple harmonic oscillation. Furthermore, how can the general formulae of SHM be adapted to suit a scenario of an AC ...
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### Validity of Kirchhoff's current law

Is Kirchhoff's current law valid for rapidly varying currents such as a one with a frequency in the order of 10KHz?
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### Triphasor Problem

Given the data presented in the following link I have to get $R$ for $P = 90~\textrm{kW}$ and the line currents $i_1$, $i_2$ and $i_3$. Any ideas?
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### If a purely inductive circuit is started in presence of gravity, will the power source ever run out? [closed]

I have read that purely inductive circuits do no work. So if an Inductor with an AC source, coming from an inverter is set up, will the source of power ever run out due to work against gravity? This ...
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### Voltage and reactive power

Why are reactive power and voltage related? When the control system of a generator increases/decreases the current of the rotor, voltage and reactive power are increased/decreased.What is the relation ...
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### How does current split in a parallel circuit? [closed]

I'm having trouble understanding why the current that goes through the 6 ohm resistor is 1A when the proportion of the parallel resistors is 2:1 from top to bottom. Could anyone explain how current ...
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### Why fuse needs to be slightly more able to bear current than the appliance?

if I have a bulb with rated current of $4 A$ then why I need to connect an $5A$ fuse?( which has slightly more ability to bear current.)
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### Equivalent DC circuit with charged conductors

I am trying to find equivalent circuit for a circuit composed of interconnected capacitors when isolated pieces of conductor may carry nonzero electric charge, and I have been struggling with this ...
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### power in an ac circuit - difference between in series and parallel

In AC-circuits, we have different kinds of power: active power $P$, reactive power $Q$ and apparent power $|S|$. Let's say we have a circuit with a resistor $R$ and an inductor $L$. My understanding ...
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### How to find when an LRC circuit is critically damped mathematically, given a set of voltage/time data?

In an undergraduate-level experiment to approximate the resistance at which an LRC circuit system is critically damped, I found the resistance range within which the system is likely to be critically ...
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### What is reactive power?

I am trying to understand what is reactive power. I have read that it has a relation with voltage, that is has a relation with the creation of a magnetic field in a motor, that it is coming and going ...
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### How Calculate the electric field into capacitor [closed]

Hello i have a problem with this exercise with capacitor, I have to calculate the electric field between the capacitor plates (neglecting the edge effects ), but I do not know how to do Text: A plate ...
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### Does electron drift model apply to current in liquids

The electrons in a metallic conductor, tend to drift at abysmally slow speeds, but still a current is able to flow through it, because the net movement is in the direction of the applied emf. How is ...
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### Resistance vs Power experiment - not linear relationship? [closed]

Ok, so I have been performing a lab experiment in class involving resistors. We were asked to set up 3x 47Ω resistors in 6 different combinations in a circuit with a 6V power supply. We also attached ...
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### Is there any intuitive or mathematical explanation to this case regarding Kirchoff's second law?

I was trying to prove Kirchoff's Voltage law, which says that in a series circuit, $\Delta V_{battery} = \Delta V_1 + \Delta V_2 ... + \Delta V_n$, where n is a number of resistors. Before proving ...
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### Current in parallel circuit and short circuits

I would like to ask a question which is partially addressed in this question: Current in Parallel Circuits Since the voltage in parallel is constant, why is it that when there is a short circuit, no ...
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### Continuing on voltage drop across a resistor [closed]

What exact wire diameter allows approximately $6.25\cdot 10^{18}$ electrons to pass in 1 second? Will a thinner diameter or a wider diameter wire allow the same approximate number of electrons in a ...
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### $P=VI$ and $P=V^2/R$ [duplicate]

How come equation a) $P=VI$ says if you double voltage, power is doubled while according to equation b) $P=V^2/R$ says power quadruples? Which one is correct?
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### How does a capacitor get charged while the charger circuit isn't closed? [closed]

a capacitor is a very known device in circuits that can be used as a short-time battery by charging it using another source, but how does it really get charged? if the plates of the capacitor don't ...
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### Resistance D-C circuit [closed]

This question seems simple, but gives two plausable answers: On your first day at work as an electrical technician, you are asked to determine the resistance per meter of a long piece of wire. The ...
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### Voltage Drop and Current Flow

Assume we have a source @100 DC volts in series with a 200 ohm resistor. According to Ohm's Law, current flow in 0.5 amps. Voltage drop across this resistor is 100 volts and equal to the source ...
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### If connecting an ammeter in parallel will cause short circuit, why won't connecting it in series does?

short circuit will happen when there is nearly no resistance in a wire, and when a high current almost infinite flowing through the wire, causing high temperature. But connected in series, an ...
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### Can someone explain me these doubts regarding voltage in an intuitive way?

This is something I have been thinking for a while. At my level, I don't know much about electric fields. Now, I will be asking two questions: One for series circuit, and the other for parallel. ...
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### Why do we say that there is a voltage drop only when charge passes through a resistor? [closed]

This is a little confusing for me. I will just ask a few questions: First: Am I correct in saying that while traversing through the circuit, charge looses some electric potential(not energy) at ...
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### Ammeter range and shunt resistance

Its said that for an ammeter to give good reading, the full current in the circuit must pass through it. But if I am right, the ammeter is basically a galvanometer connected parallel to a very low ...
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### Why do we prefer using materials of high resistivity in laboratory instruments?

I know that :$$R=\rho\frac{l}{A}$$ where $R$ is the resistance of the wire, $\rho$ is its specific resistance (resistivity), $l$ is its length, and $A$ is the area of cross-section of the wire. Why ...
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### How can the copper wire in an electricity generator provide an infinite number of electrons? [closed]

How can copper wire in an electricity generator produce an infinite number of electrons when the is a finite number orbiting each copper nucleus?
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### Short circuit in superposition

I'm really confused about the concept of short circuits. I don't understand, why when you short those two voltage sources, 20 and 10 ohm resistors become parallel? What happens with 4, 12, 15 ohm ...
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### Using superposition to find current

I'm given the following problem I'm a little bit confused about superposition problems when current flows through a voltage source but not the resistor. 1) When I looked at the solution for this ...
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### Alternating current. Resultant force

I've just been wondering: In an alternating current, the direction of the current is constantly changing. This implies that the acceleration of the charge carriers is constantly changing (pos. neg. ...
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### If current is same, is it correct to say that the speed of charge passing through a resistor is more than that of a normal wire?

It took me a long time to understand that current is constant throughout the circuit. And now I am stuck at one last thing: The speed of charge. Here is what I am thinking: Current is defined as ...
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### Voltage across a resistors

When i was doing the practice problems, I found the following problem: I was able to solve for everything except for V4. When I looked at the solution manual,solution was as follows: Use KVL: V4 = ...
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### Why is the force from an electric resistor linearly proportional to the drift velocity?

In a circuit, the potential difference across a resistor is given by Ohm's Law as V=IR. Since the potential difference is the loss of potential energy per charge and the force is -dU/dx, we get that ...
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### How does the energy remain conserved in a transformer?

The induced voltage in the secondary coil of a transformer is given as $\frac { { N }_{ S } }{ { N }_{ P } } *{ V }_{ P }$ (where ${ N }_{ P}$ and ${ N }_{ S }$ are the number of turns in the primary ...
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### Why does a battery die more quickly when more resistors are added to the circuit?

I will be explaining what I think: A battery acts like a pump which provides energy to do work on negative charges to move them towards the negative terminal, and hence creating an electric field. ...
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### Solving for node voltages

I have the following circuit and i need to solve Is, v1 and v2. First of all, I assumed that this problem will involve supernode principle since there is a voltage source between V1 and V2. Then, i ...
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### Does the internal resistance of a battery dissipate heat as expected?

A common real battery is often modelled (to a good approximation) as a perfect voltage source having emf $\varepsilon$ with a series internal resistance $r$. So, when a current $I$ is drained from it, ...
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### Thevenin equivalent voltage and resistance of a circuit: verification needed

Here is my reasoning: We have to sources so me must use superposition: We first replace the current source by its resistance which is infinite for an ideal current source. Now we need to measure ...
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### Finding the equivalent resistance

I'm having hard times understanding why when you combine 20 and 30 resistances which are in parallel, and then combine 60 and 40 (which are also in parallel) ohms resistances you will get two parallel ...
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### How is a variable potential divider able to reduce current/voltage through a component to zero, unlike a variable resistor?

For example, the diagram in my text book shows a filament lamp, in series with a uniform resistive wire, which can have its voltage and current varied by moving the sliding contact, e.g., a ...
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### Circuit with three capacitors

A potential difference of V = 38.0 V is applied across a circuit with capacitances C1 = 4.1 nF, C2 = 4.7 nF, and C3= 2.3 nF, as shown in the figure. What is the magnitude and sign of q3l, the ...
### Why is resistance $U/I$ rather than $I/U$?
What is the difference between resistance and conductance and why is resistance $U/I$ and not $I/U$? (I know $I/U$ is conductance.) But I don't see the difference between both.