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Questions tagged [capacitance]

The ability of an object to store electric charge.

Often the concept capacitance is applied to two separated conductors, as a potential difference between them is applied. The SI unit for capacitance C is farad (F).

$${C={Q}/{V}}$$

Where Q is the charge in the object and V is voltage across the two conductors.

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Why do we use capacitors and not batteries in defibrillator?

Why do we use capacitors in defibrillators and not batteries? I know that capacitors are used to store electrical energy but isn't the function of a battery just the same? Moreover, I know that batteries are used to make capacitors work in a…
musicinmyheart
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Intuitively, why does putting capacitors in series decrease the equivalent capacitance?

Can someone please explain, intuitively (without any formula, I understand the formulas), why the equivalent capacitance of capacitors in series is less than the any individual capacitor's capacitance? Let's take a simple case. Say we have 2…
An Ignorant Wanderer
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How is energy "stored in an electric field"?

My physics teacher told me the statement "The energy of a capacitor is stored in its electric field". Now this confuses me a bit. I understand the energy of a capacitor as a result of the work done in charging it, doing work against the fields…
anon
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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?
Bálint Tatai
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What is the electric field in a parallel plate capacitor?

When we find the electric field between the plates of a parallel plate capacitor we assume that the electric field from both plates is $${\bf E}=\frac{\sigma}{2\epsilon_0}\hat{n.}$$ The factor of two in the denominator comes from the fact that there…
Pricklebush Tickletush
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Why is capacitance defined as charge divided by voltage?

I understand that capacitance is the ability of a body to store an electrical charge and the formula is $C=\frac{Q}{V}$. What I don't understand, however, is why it is defined as coulomb per volt. Of course, the charge in the numerator makes sense…
Richard Smith
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Field between the plates of a parallel plate capacitor using Gauss's Law

Consider the following parallel plate capacitor made of two plates with equal area $A$ and equal surface charge density $\sigma$: The electric field due to the positive plate is $$\frac{\sigma}{\epsilon_0}$$ And the magnitude of the electric field…
Gerard
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Why does the voltage increase when capacitor plates are separated?

In lab, my TA charged a large circular parallel plate capacitor to some voltage. She then disconnected the power supply and used a electrometer to read the voltage (about 10V). She then pulled the plates apart and to my surprise, I saw that the…
Toby
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How can supercapacitors not implode?

How can supercapacitors store $5\,\mathrm{coloumbs}$ and not implode due to the enormous force between the plates ($10^{15}\,\mathrm{N}$ if the plates are $1\,\mathrm{cm}$ apart)?
moonblink
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What is the difference between a battery and a charged capacitor?

What is the difference between a battery and a charged capacitor? I can see lot of similarities between capacitor and battery. In both these charges are separated and When not connected in a circuit both can have same Potential difference V. The…
claws
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Why Is Capacitance Not Measured in Coulombs?

I understand that the simplest equation used to describe capacitance is $C = \frac{Q}{V}$. While I understand this doesn't provide a very intuitive explanation, and a more apt equation would be one that relates charge to area of the plates and…
Ethan Dandelion
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Is there a deep reason why springs combine like capacitors?

I was solving a practice Physics GRE and there was a question about springs connected in series and parallel. I was too lazy to derive the way the spring constants add in each case. But I knew how capacitances and resistances add when they are…
user34801
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Are there analogs to resistance, inductance, capacitance, and memristance connecting the weak force to electromagnetism?

A question was asked over at EE.SE recently which I tried to answer, but much of my answer was speculative. I'm hoping someone here can help my ignorance. In electronics design, there are four physical quantities of interest: voltage, flux, charge,…
Stephen Collings
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Distorted colors of Google StreetView photographs near electric power lines

This is a followup to my question: Cyclist's electrical tingling under power lines Some users presented a convincing picture that the electric shocks under power lines are primarily from the electric fields, not the magnetic one, because the…
Luboš Motl
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How does current flow in a circuit with a capacitor?

When a capacitor is connected to a battery, current starts flowing in a circuit which charges the capacitor until the voltage between plates becomes equal to the voltage of the battery. Since between plates of a capacitor there is an…
Dario Mirić
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