# Tagged Questions

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

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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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### Definition of equivalent capacitance

I know that equivalent capacitance of multiple capacitors in series is $$C = \left(\frac{1}{C_1} + \cdots + \frac{1}{C_n}\right)^{-1}$$ and in parallel is $$C = C_1 + \cdots + C_n.$$ But there are ...
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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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### 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 ...
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### 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.
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### Why do we consider current to be constant throughout a circuit? [duplicate]

Let us consider a circuit made up of connecting wires, a resistor, a switch and a battery. Now, the resistance of the resistor is much higher than that of the wire. Now, intuitively, I am thinking ...
165 views

### The sign of the current flowing in a circuit

I was doing the following problem: And I was asked to find Iy. I found Iy to be 2.64 using KCL. However, the right answer was negative 2.64. Is it negative only because there is a dependant ...
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### Why does a variable potential divider have the ability to reduce current through a component to zero

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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### How is a potential divider able to reduce current to zero?

For example, a filament lamp, in series with a uniform resistive wire, can have its voltage varied by moving the sliding contact, e.g., a rotatable wheel. However, why is a potential divider able to ...
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### Capacitors and external electric fields

I am grading questions from the lab manual provided by the professor to review with the students. I am trying to wrap my head around one of the questions about what an external electric field would ...
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### What exactly is potential difference? What are the factors that effect it?

I am asking this question because at first I thought that this concept was pretty clear to me, but it is not. So, my first question: Is potential difference only a property of an electric field? If ...
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### Are diodes (or FETs) electrets?

The explanations I see of diodes and FETs seem to involve various depletion regions, migration of electrons and holes, and the such. My (perhaps naive) interpretation of these explanations implies ...
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### The separation between the two plates of a capacitor is increased

I had the following question on a quiz recently: A capacitor consisting of two parallel plates, separated by a distance $d$, is connected to a battery of EMF ε. What happens if the separation is ...
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### $P=V^2/R$ confusion

I am confused on how to apply the formula $P=\frac{V^2}{R}$ If I am given a bulb say with power 60W and it is connected to a supply of 120V. Then the resistance of the bulb is 240$\Omega$ but if ...
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### Why is Kirchoff's Voltage Rule not satisfied when the circuit is shorted?

For example if I have a simple circuit with a battery and a resistor, and then the resistor is shorted, Kirchoff's Rule is no longer satisfied. Since the current through the resistor is 0, the voltage ...
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### Why didn't 0.2A at 2V kill me? [closed]

I was recently connecting a circuit together like here: and I had the voltage set at 2V, with a 10Ω resistor. By Ohm's law, there was a current of 0.2A (and was confirmed by my multimeter). I ...
6k views

### Capacitor Charging and Discharging when connected to the ground

When we charge a capacitor using a battery and then remove the battery, the plates of capacitor becomes charged. One holds positive charge and the other one gets equal negative charge. o. k. ? Now ...
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### How to find the current source Is and the voltage V1 of this circuit schematic? [closed]

I have Vs= 1.5V, R1=1 Ohm, R2 =6 Ohms, I got the equivalent resistance to be 7 Ohms. Then I set equal Req to Vs for 7I=1.5 and got my current source to be 0.214A. Since it is only Vs and Req in the ...
16k views

### What is Electromotive force (EMF)? How is it related to potential difference?

What is Electromotive force (EMF)? How is it related to the potential difference? Is it created by the potential difference in any conductor? Is it a process? Why is it called force? Does writing EMF ...
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### If the electric potential is location dependent, why do charges loose it when passed through a heavy resistor in a circuit?

I really cannot understand this: I know through reading that unlike electric potential energy, which is charge dependent, the electric potential is purely location dependent. For example: If at a ...
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### If there is a potential difference between the ends of a battery, does it mean that there is always an electric field?

First of all, I am really sorry if this question is wrong. But, I thought that this would be the best place to ask this. Here is what I am thinking: Batteries promote flow of current in a circuit due ...
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### How to think about Ripple and Noise in circuits

Say you have a AC to DC power supply. If you were to hook an oscilloscope up you would see noise occurring. Some of it would appear to have a regular frequency in Khz or Mhz. Would this put off EM ...
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### Voltage across voltage source in a short circuit

When we short-circuit a voltage source, the current will be very high. The voltage across the wire is 0V. If we apply KVL, also the voltage across the voltage source is 0V. How can it be 0V if we have ...
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### Ohm's law experiment

I was going through my physics laboratory manual. In the Ohm's Law Experiment, the book states a few precautions without any reasoning. 1.The wire whose resistance has to be determined should ...
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### Calculation Equivalent Resistance In A Circuit With resistances connected in a circle [closed]

I am having trouble in finding the equivalent resistance between the terminals 'a' and 'b' in the following circuit: Please can anyone explain to me how to solve such problems. Thank You!
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### Why does energy flow between a high voltage transmission line and linemen approaching it on a helicopter?

The video High power line workers shows linemen servicing a live high voltage transmission line. As the helicopter approaches the line, the lineman reaches out with a metallic wand that is ...
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### Why is a series resistor needed in a simple thermistor experiment? [closed]

I have come across the following simple question, however I can't see any need for a fixed resistor in series. The only possible reason that I can think of is that the resistance of the thermistor ...
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### How to control a dc motor? [closed]

I am in 8th standard and I am doing a project on 3d printing pens. I want to know how to control a dc motor, so that when I press a button it should increase its speed gradually till it reaches its ...
120 views

### Voltage of a battery in a circuit with an infinite resistance [closed]

I have a dilemma that I would like to share with you concerning batteries (without neglecting internal resistance), emf and resistance of a circuit. To better visualize my question you may need to ...
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### Help to solve a circuit with capacitor and resistor

Till now I'd never solved a circuit with resistor and capacitor. I'd seen the problem and tried to solve. But now I am in a doubt.The circuit was like that- My attempt-
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### The equivalent resistance betweeen A and B. I need the answer with proper explaination [closed]

how are we supposed to do this question if resistance is given as 1 ohm