# Questions tagged [voltage]

Voltage is the unit of measurement for electronic potential, from one point location to another.

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### Is electric force constant all over the surface of a conductor?

This question was asked in IIT JEE 2010. I know that the electrostatic pressure is equal to (1/2)∈(E)² and if we multiply this with the projected area then we would get the force acting on an object ...
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### How do you measure voltage from first principles? [closed]

I've always wondered if you were thrown back in time with just my cell phone, how could I charge it... I know how to make electricity, but how do I check the voltage if all I have access to is, shall ...
2k views

### 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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### 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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### Different definitions of the EMF of a device - None of them applies to devices in a circuit

Wikipedia gives two formal definitions of the electromotive force: One in case of a closed loop, in which case the the EMF is supposed to be the path integral of the electric field (and all other ...
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I was looking at past exam papers and found a question that I can't understand. It is basically about current flow but the diagram is really confusing me. The diagram is the following: The question ...
12k views

### Will the volt, ampere, ohm or other electrical units change on May 20th, 2019? [duplicate]

When watching a video by Veritasium about the SI units redefinition (5:29), a claim that the volt and unit of resistance (presumably the ohm) will change by about 1 part in 10 million caught my ...
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### Electric potential and voltage

A capacitor is connected to a battery with constant voltage. If you approach one of the plate to the other, what happens to electric potential? I already have an answer to this question but it's ...
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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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### 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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### 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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### Does the voltage of the battery change if you use it? [closed]

If you use the battery to charge a capacitor does the voltage of the battery decrease or still the same? Does the voltage of a capacitor decrease if you use it to charge another capacitor?
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### Why does a voltaic cell induce an electric force proportional to voltage?

I'm trying to understand the intuition behind Ohm's law (that current is proportional to voltage). I understand the basics of the Drude model: if the electrons frequently collide and on average reset ...
444 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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### Can the mains voltage affect laser intensity?

First of all in very new to the photonics field and i am only venturing into it because I have to troubleshoot an experiment and the issue seems to be the optics block. So i am using an instrument ...
138 views

### Why doesn't electric field of an electromagnetic wave cause an electric shock?

An electromagnetic wave can have an electric field magnitude of more than 1000 V/m, which is a very high potential difference. When the light shines on you, why don't you feel an electric shock?
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### 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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### 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, ...
52 views

### Calculating the potential difference of a capacitor [closed]

As far as I know the voltage between the plates of a capacitor will be reduced due to discharging. I wonder how much the voltage would be changed if the capacitor lost %25 of its stored energy. ...
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### How is voltage (potential difference) like gravitational potential energy? [closed]

How is voltage (potential difference) like gravitational potential energy? What are their similarities
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### How does the $I$-$V$ curve for bulk metal look like?

For semiconductors, the current (I) vs. voltage (V) relationship is as shown in the picture below. As we increase the applied voltage, the electron-hole pairs generate increases too, so we see an ...
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### Why isn't $V_L$ not equal to $i_LR_L$ according to Thevenin's theorem?

According to Thevenin's Theorem $I_L= \frac{V_{th}-V_L}{R_g}$ whereas $I_L$= current through the load. $V_{th}$= The potential difference across the load resistance when the load resistance is ...
10k views

### What *exactly* is electrical current, voltage, and resistance?

I am taking AP Physics right now (I'm a high school student) and we are learning about circuits, current, resistance, voltage, Ohm's Law, etc. I am looking for exact definitions of what current, ...
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### Why do 2 charged conductors gain same potential when connected via wire

Why do 2 charged conductors gain same potential when they are connected via a wire.Can somebody also give a mathematical proof of it?
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### How do resistors form electric fields and thus potential drops?

$$V_{ab}=-\int_b^a\vec{E}*\vec{dl}=\int_a^b\vec{E}*\vec{dl}$$ By Kirchhoff's loop rule, the sum of the potential drops across a closed loop is zero. Going in the direction of conventional current ...
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### Deriving the formula of potential difference duo to a solid conducting sphere

The doctor in university was deriving a formula and I can't understand how it works A sphere with charge Q The Sphere's radius is R, and we are trying to derive a formula for potential difference at ...
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### Convert graph of voltage to electric field lines

I have a physics lab which involved connecting wires to two points on a conductive paper and supplying a voltage. We measured the voltage at every point on the paper and made a graph of the results. ...
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### Why is high voltage dangerous?

High $V$ low $A$ electricity is transformed into low $V$ high $A$ through a step down transformer for safer use in homes. But how is it any safer? The wattage is the same for the pre-transformer ...
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### The formula of voltage

Definition from Wikipedia: An electric potential (also called the electric field potential, potential drop or the electrostatic potential) is the amount of work needed to move a unit of positive ...
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### Why electron can go through PVC insulator

I connected a PVC insulated alligator clip test lead to a 12V (give 20V) DC power supply positive terminal and a multimeter. After that I connected an other one to the multimeter ground, and a third ...
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### Why does the Voltage of a Capacitor change in an alternating current (AC)?

I have a question about charging a capacitator in an alternating current. If the process starts the current charges the capacitator, therefore the voltage on the capacitator will be increased. Now the ...
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### How does an alternator produce AC?

As an alternator’s coil moves, one side of the coil induces a voltage and thus a charge flow in one direction However, simultaneously the other side of the coil induces a voltage and charge flow in ...
218 views

### Why does the potential along a uniform current-carrying wire vary with the distance along it?

Is it because as the electrons move further through the wire they lose more energy due to resistance? Also, in this context, I believe potential refers to the electric potential energy but I am unsure,...
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### Insertion of an electric component in a resistance connected to AC supply

Kindly ignore the written matter... I don't understand, how the current would remain the same even after a capacitor is introduced in the circuit... This is what I did: The current after insertion ...
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### Minimum Voltage to Sustain an Arc

I've read that after a plasma channel is created in air, the resistance decreases significantly and the arc can be sustained with a much lower voltage, as long as the heat dissipated by the plasma is ...
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### Is the voltage between the two points $A$ and $B$ denoted as $U_{AB}$ or $U_{BA}$? And why?

Consider the following circuit Is the voltage between the two points $A$ and $B$ denoted as $U_{AB}$ or $U_{BA}$? And why?
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### Motional EMF with a rod in a closed loop

Let me preface this by saying that while this is a problem which came from my college physics class, it was not a graded assignment, it was optional study material (and you can see from the photo I've ...
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### Derive the formula for a capacitive voltage divider?

I've seen the derivation for a resistive voltage divider, Vout = Vin * R2/ (R1 + R2). For a capacitive divider, Vout is reported as Vout = Vin * C1/ (C1 + C2) - for example see https://en.wikipedia....
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### Why does photocurrent increase with voltage for a while?

Consider a photoelectric setup as below to investigate the maximum kinetic energy electrons. When we graph photocurrent against the voltage applied against the electrons moving, why does the ...
567 views

### Difference between voltage, electrical potential and potential difference

I am having hard time to visualize these two concepts in my mind seriously. First of this confusion came from two parallel plates that was connected to a power supply, charged then disconnected from ...
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### How Work =Voltage * Charge? [closed]

We know, Work/charge=volt So work =volt*charge But work =Fd So my question is since both voltage and charge are not dependable on distance,so how come work can be calculated without factoring in ...
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### Understanding Kirchhoff's Loop Law

I'm trying to understand how voltage works in circuits, and currently I'm stuck at Kirchhoff's Loop Law. Suppose we have a simple circuit, just a battery and a resistor. Our battery supplies a ...
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### Understanding the potential difference of a wire

I'm trying to understand the fundamentals of potential difference in circuits. My understandings (from textbook and stackExchange): Potential difference is created by a separation of charges. A ...
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### Electric field and potential [duplicate]

Suppose we consider a point dipole i.e. an ideal dipole. At the origin the potential: $$\phi(\mathbf r) = \frac{1}{4\pi\epsilon_0} \frac{\mathbf p\cdot\hat{\mathbf r}}{r^2}$$ is undefined due to ...
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### Method of Images conundrum

My lecturer and I have found separately valid solutions to Poisson's equation in the region of interest for the following problem: Here is my interpretation of the boundary conditions: V(x,y,z \to ...
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### Summing up very basic terms in basic electricity [closed]

My attempt to define following terms as per my understanding. I am currently at high school. Electromotive force (EMF): Potential between two terminals when open circuited. Wikipedia's ...
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### 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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### Potential in open branch of a parallel circuit with grounding [closed]

If the switch is still open, what will the electric potential at Q be, i.e. negative, positive or zero? Is there a potential difference across the grounded point and point Q, or R3, even though the ...
### 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} = ...