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Questions tagged [voltage]

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

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29 views

Confusion about non-ohmic conductors

Could someone please explain what happens in a non-ohmic conductor when the voltage is dropped in terms of current and resistance? It would help me a lot if it were done in detail. I don't understand ...
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Confusion about the relationship between current, resistance and potential difference

If the voltage of a component has dropped, what will happen to the resistance? My book says it will decrease but I don't understand the logic. How can current and resistance go down at the same time? ...
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Confusion about Ohm's law

So does ohms law say if the resistance is increased the voltage will also increase but not the current? And in non ohmic conductors the current increases with the voltage even though the resistance is ...
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10 views

Inverting Amplifiers in Circuits

In layman's terms, what are inverting amplifiers and why are they necessary? How can you take a circuit that has an inverting amplifier like the one below and convert it to be a normal circuit? What ...
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1answer
25 views

Using ammeter to measure voltage

Suppose you have the following circuit: Where R1 = 1 kΩ, R2 = 2 kΩ, R3 = 3 kΩ, R4 = 4 kΩ, R5 = 5 kΩ, Vs = 5V. The voltage in the branch with R5 is then 5 I where I over R5 is .064A. Suppose you ...
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When to use $e^{-t/RC}$ - Capacitor discharge and charge

Respected Team Members, I am learning how to calculate the amount of time it takes to charge/discharge a capacitor. The Formula given in the text book is $$\ V_{f}=V_{s}(1-e^{-t/RC})$$ But we ...
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1answer
35 views

Why can two nodes at the same potential be collapsed into one node?

I have a problem where I have a cube with resistance $R$ along each edge. I am asked to find the potential between various nodes (corners) using symmetry and the fact that two nodes at the same ...
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2answers
34 views

Voltage Change Across a Resistor/Circuit

Say you have a 9 volt battery, and you connect the two ends of the battery with a wire to form a circuit with no resistor. If you measure the potential difference between the two ends of the battery, ...
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2answers
37 views

Proof of continuity of voltage across a capacitor

It is known that the voltage drop across a capacitor is a continuous function of time. This means that, for each instant t0, we may write: V(t0-) = V(t0+) This relationship is very used in the time ...
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31 views

Diode as a voltage source [closed]

We have known that diodes cannot be used as a voltage source. Eventhough is has a constant barrier potential depending on material used. Why can't we use an unbiased diode as a voltage source?
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13 views

Oscilloscope and Multimeter working principle [closed]

How do Multimeters measure voltage? How do Oscilloscopes measure voltage? Is there any difference?
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1answer
21 views

Point with 0 electric field and non-zero potential

I'm quite new to physics and I don't totally understand the concepts of potential energy and work. I've been watching MIT courses and I got pretty confused, considering the following situation: We ...
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2answers
35 views

Confusion in usage of formulae for power dissipated in a circuit

When should we use $\frac {V^2}{R}$ and when to use $I^2R$. Because many times they ask about the power without giving details about series and parallel. I am really confused
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1answer
60 views

Voltage measurement

Why does multimeter show 0 V ?
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1answer
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Meaning of negative emf in the context of Kirchhoff’s Voltage Law

I’m wondering what it means when the emf of a battery is calculated to be a negative value through Kirchhoff’s Voltage Law. This is the problem: As you can see, we’re given the currents, and we can ...
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2answers
49 views

How does a capacitor charge if there is zero voltage across it?

From what I understand, a resistor causes a voltage drop. So it would seem that the end of the capacitor attached to the resistor would have the same voltage as the end attached to the battery. If ...
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3answers
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If voltage represents an energy difference between two points, why don't electronic appliances all use the same amount of energy?

As I understand it, voltage is an energy difference between two points. $$V_f - V_i = - \int \mathbf{E} \cdot d\mathbf{s}$$ But consider a toaster and a refrigerator each using their own 120V ...
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6answers
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Potential difference and current

According to Ohm's law: $V=IR$. Therefore $V$ is directly proportional to $I$. Furthermore, $V=W/q$ and $q=IT$. Thus $V=W/IT$. Therefore $V$ is inversely proportional to $I$. How can $V$ be both ...
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52 views

What happens to resistance if we double current intensity?

problem: what happens to resistance if we double current intensity ? my attempt: ohm's law tells us $R = { V \over I }$ so : $${R \over 2} = { V \over 2I }$$ so resistance should decrease to half ...
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Can i have voltage in a MOSFET with the gate only connected to the positive terminal of a battery?

I am struggling with the intuition of why I can't leave the gate only connected to the + terminal of a battery: In my understanding, until equilibrium electrons would still flow towards the + ...
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2answers
42 views

In the Volta potential or Nernst potential equations, where does the logarithm come from?

In both Volta potential and Nernst potential equations, besides some constants, temperature and valence parameters, the potential is a function of the logarithm of the ratio of two densities (or ...
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0answers
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Thevenin’s Theorem (confused) [duplicate]

I’m not really asking for a proof here but I just feel like I’m getting something wrong with this theorem.On the diagram below...from what I read Vs=VAB. Note that Vs =« Thevenin’s Voltage » and Rs=« ...
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4answers
101 views

Confusion about this simple electrostatics line integral

Suppose we want to find the electrostatic potential $\phi_{0}$, with reference to infinity, at $r_{0}$ resulting from a positive charge $q$ located at the origin. For simplicity, let us assume we are ...
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0answers
18 views

How current flows in an ideal wire when there is no potential difference? [duplicate]

Such as in this case: Even though potential difference between points A and B is zero, a current of 9A will flow between these two points. Why it is so? I understand potential difference must exist ...
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14 views

Relation between output voltage and pressure field from a piezo

When applying a sinusoidal voltage with an amplitude $V_{pp}$ and a frequency $f$ across a piezoceramic transducer, the piezo vibrates and generates pressure fields. Is there a formula for the ...
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1answer
42 views

How the earth keeps the electric potential?

I have the following DC circuit. A cell and a resistor (lightbulb) is serially connected and both ends are grounded. I see the lightbulb is on and hence the current flows. It is because the electric ...
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31 views

Power voltage relation

I have a question concerning the relation between power and voltage. We have a lamp with power of 36W when used with 12V. With what power does the lamp work if we connect it to a 6V battery? First,...
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1answer
53 views

Phases of current and voltage

Why $u(t)$ and $i(t)$ are in the same phase in a resistor, but in a condensator $i(t)$ is ahead of $u(t)$ by $\pi/2$, and vice versa in a coil? Note: I need physical explanation, like main reason of ...
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2answers
50 views

Why the potential across the voltmeter is not affected by changing metals? How can we prove it?

A voltmeter has both its leads made of metal Cu. When connected across a battery, it measures a voltage V. One of its leads is replaced by metal Au. But the potential across the voltmeter is not ...
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4answers
81 views

Current and voltage [duplicate]

I am current studying A level physics. I know that current is the same in all parts of a series circuit, however I cannot understand why. If adding resistance to the circuit causes the kinetic energy ...
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1answer
42 views

Does the length of wire affect?

I find the voltage of electric wire in between point 1 and point 2. I want to know if I use the differrent wire,long one and short one,the voltage will be equal or not?
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1answer
40 views

What electric field will act in the vacuum between two closely placed metal plates with saw-tooth voltage applied to them?

If two parallel metal are placed very close to each other and a saw-tooth voltage is applied in the plates, how will the electric field behave in the vacuum in between the plates? As the separation ...
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2answers
73 views

Why strong electric field leads to non-Ohmic behavior?

Homogenous conductors like silver or semiconductors like pure germanium or germanium containing impurities obey ohm's law within some range of electric field values. but if the field becomes too ...
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1answer
68 views

What exactly does Ohm's law say?

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, R ...
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1answer
51 views

Relation between electric potential and Electric field

I'm unable to understand why the integration of $\mathbf E$ is done in two different ways for constant $\mathbf E$ and varying $\mathbf E$, as in case of parallel plate capacitor and spherical ...
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4answers
82 views

Ambiguity between electric potential and voltage?

I understand that electric potential is a location based measure of electric potential energy per unit charge in an electric field, and that voltage is then the difference between two electric ...
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1answer
44 views

Is the current on one side of the bulb more than the current on the other side of it?

Go easy on me if you find this question stupid, just another high schooler here. So here's what I am thinking.A battery "pushes" electrons through a circuit due to the electric potential difference ...
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27 views

Electric field inside a homogenous distribution for slightly different Coulomb's law

I am trying to show that the electric field inside a homogeneous distribution of superficial charge is of the order of magnitude of $\delta$, with: $$V(\textbf{r})=\int d^3\textbf{r'}\frac{\rho(\...
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1answer
75 views

Why connect plug wires in a certain way when polarity changes in AC anyway? [duplicate]

In AC systems the two wires of a circuit alternate polarity many times per second. So positive and negative switch, half of the time a wire is positive the other it is negative. So why is it ...
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1answer
48 views

Current in RC circuit

Why is current drawn in an RC circuit (in a circuit powered by DC voltage supply) independent of the capacitor used? While the capacitor is charging current drawn from the battery only depends on ...
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2answers
33 views

Components of Electrostatic energy to components of electric field?

I'm trying to understand the relationship between electrostatic energy and the electric field so that I can compute electric field components from electrostatic energy components. Is it correct to ...
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1answer
37 views

What is causing the current sinusoidal delay regarding voltage in inductive circuits? [duplicate]

Do electrons acquire some electromagnetic 'mass'as they have so much slow acceleration in the coil due to obviousely electromagnetic field acting on them or it is just the net voltage that drops down ...
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3answers
101 views

Basic question on Ohm's law

I have what I assume is a very basic question on Ohm's law. Let's say that we have $n$ equal light bulbs in a series with a battery. We know that $$ U - IR - IR - \cdots -IR= U - nIR = 0.$$ Solving ...
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1answer
43 views

Significance of the negative sign in $V=-\int \vec E · \mathrm d\vec r$ [duplicate]

Why is there a negative sign in the relation $$V=-\int \vec E · \mathrm d\vec r$$ between the electric field and the electric potential? Is this because of some derivation in vector calculus because ...
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3answers
360 views

What happens when electrons reach the battery?

We have a capacitor which is connected to a voltage source. The top plate of the capacitor is connected to the positive terminal of the source. Therefore, electrons go from the top plate to the ...
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4answers
106 views

Why does inductor current lag the applied voltage at its terminal by 90 degrees?

I studied electromagnetism and I am currently working with Inductors. I could not figure out the physical reason based on electromagnetics on why inductor current lags the applied voltage by 90 ...
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0answers
71 views

Voltage propagation along a wire [closed]

Let's say you have a wire connected to a device that you can switch between high-voltage and ground voltage. The wire is not connected to anything on the other end. You're observing the voltage in two ...
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0answers
20 views

Open circuit voltage of solar panel in relation to temperature

How do we calculate the effect of temperature on the open circuit voltage of a solar panel? The source: https://www.pveducation.org/pvcdrom/solar-cell-operation/effect-of-temperature offers an answer,...
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4answers
74 views

What is the intuitive explanation for high voltage and low current?

By the formula $$P=VI$$ we can say that the voltage can be increased and the current decreased by keeping the power constant. It is mathematically and experimentally right. But is there a way to ...
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1answer
49 views

What does Ohm's law mean in this context?

In this problem Griffiths states that the potential at radius $a$ and angle $\phi$ is $V(a,\phi) = \frac {V_0 \phi}{2 \pi}$ And yes that satisfies the boundary conditions, that at $ \phi = \pi$ , $ V=...