The ability of an object to store electric charge.

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Electric field intensity in a dielectric inside a capacitor

In the question A parallel plate capacitor is charged from a cell and then isolated from it. A dielectric slab of dielectric constant $K$ is now introduced in the left half region between the ...
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0answers
37 views

Force exerted by a capacitor on a polar object

I was reading about capacitors and wondered what the force an electrostatic field created by a capacitor would be on an object with a certain charge and mass. If it can exert a force on a polar object ...
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1answer
79 views

How to get a function for the voltage across a capacitor connected to an AC voltage source? [closed]

I am looking for the way of obtaining a solution for $V_{c}$ ,as a function of $t$ depending of $\omega$, of the following differential equation related to an electrical circuit involving a low-pass ...
2
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0answers
168 views

Absolute permittivity and permeability of free space

I'm reading about the propagation of EM waves in vacuum. We define the wave equation using two constants: $\epsilon_0$ and $\mu_0$. Of course they are absolute permittivity and absolute permeability ...
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1answer
672 views

How do capacitors work?

Say you have a battery, with a wire connecting the negative and positive terminal. Initially, (the transient state) the electric field is not uniform and is perpendicular to the surface of the cross ...
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3answers
90 views

Are these assumptions correct?

Is it true:From equation $C=Q/V$ 1)If Potential difference is kept constant $C \propto Q$ 2)If charge is kept constant $C \propto 1/V$ Then if 2nd is true I do have a question: Don't we say that ...
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0answers
60 views

Relation between charge and voltage in spherical capacitors

If we had a spherical capacitor and the voltage across it is 1000 V, I need to know the charge on every plate, I know 2 ways to solve this either using C=Q/V or V=Q/r * 1/4*pi*Epsilon. So, which one ...
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4answers
116 views

Why change in Capacitance?

I do know it that the overall capacitance decreases if two or more capacitors are connected in series,but do not understand why? I do understand it mathematically but don't get the physics behind it.
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18 views

Resistor connections [duplicate]

I can't figure out what kind of connection it would be if i put resistors like this Can someone please explain how they are connected, like is R1 and R2 in series and R4 and R5 in series and then I ...
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2answers
369 views

Does there exist a single plate capacitor(conductor)?

Does there exist a single plate capacitor(conductor)? if yes How will you define the capacitance and potential(difference) of such conductor?
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1answer
255 views

Parallel Plate Capacitors

I was wondering what would happen to capacitance if the plates are not parallel (above/below each other) or if the plates are not the same size. Thanks.
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2answers
897 views

Capacitors in series: Why is the equivalent charge the same as the individual charges

Consider two parallel-plate capacitors $C_1, C_2$ in series. For the "equivalent" circuit, clearly $$ Q_{equiv} = C_{equiv}V$$ should hold, where V is the total voltage drop between input and ...
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1answer
78 views

Capacitors in series?

Capacitors in series have identical charges. We can explain how the capacitors end up with identical charge by following a chain reaction of events, in which the charging of each capacitor causes ...
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2answers
139 views

Charging a Capacitor?

How is the charge +q given to the one plate to the capacitor with the help of a battery, does the battery remove electrons from the plate and +ve charge gets accumulated on one plate?Does it? And one ...
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4answers
333 views

Electric potential and maximum charge on a conductor

Does increasing the amount of electric charge on a conductor cause an increase in its electric potential to a point at which it becomes maximum; where it can hold no more extra charge? Is it true? ...
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0answers
126 views

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 ...
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1answer
42 views

Influence of a Capacitance Matrix of a voltage measurment

I am having a problem in understanding how in a multiconductor system the Capacitance Matrix influences the measure of voltage between two electrodes. In the case that interest me we have 4 ...
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3answers
210 views

electron flow in capacitor with dielectric

if I make a circuit with a battery and a capacitor (with a dielectric inside), how it is possible to get a current in the circuit? If electrons go from one pole of the battery and they arrive to one ...
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1answer
46 views

Capacitance of a free conductor

Consider a ideal conductor in free space.For all purposes here,the zero of the potential is taken at infinity. Suppose I give a charge $Q$ to the conductor.As a result,the conductor will have a ...
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1answer
1k views

Does displacement current exist after the capacitor gets fully charged?

The displacement current is due to changing electric field. Since, after the capacitor gets fully charged there is no changing electric field there is no displacement current.(capacitor connected to a ...
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2answers
45 views

Capacitance and energy

So I've been reading about capacitance (Specifically in capacitors) and I'm wondering if this reasoning is sound, and why/why not: C = Q/U U = Q/C We also know that: U = E/Q So: E/Q = Q/C Q^2 = ...
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1answer
80 views

Capacitors in parallel and dieletric [closed]

I'm trying to solve this problem: Two capacitors of capacitance $C_1=200pF$ and $C_2=1000pF$ are connected in parallel and loaded to a potential difference of $400V$. Subsequently the space ...
3
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1answer
1k views

Delta to Star/Y Conversions and vice versa in Electric Ciruits

We all know the basic rules for conversion of $"Delta"$ circuits to $"Star"$ circuits and vice versa. We also know that this is needed for simplification of circuits in complex cases. Can anyone ...
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0answers
13 views

Is this configuration correct for this spherical capacitor? [duplicate]

This capacitance contain 4 dielectric as shown in the figure dielectric 1 in half sphere and 2,3 in for 1/4 of the sphere and the fourth one in the last 1/4 of the sphere as shown and I want to find ...
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3answers
73 views

Capacitor related query

Why does a capacitor charge only upto the voltage of the source? I mean in an r.c. circuit if we have a resistor that is in series with the capacitor then because of the potential drop there will be ...
3
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1answer
114 views

Realistic vs Idealistic capacitance

I am doing an investigation into the differences of calculating capacitance using the well know formula for an idealistic parallel plate capacitor, based on the assumption of a uniformly distributed ...
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1answer
92 views

Capacitors in parallel and capacitors in series

How can I recognize clearly when I deal with capacitors in parallel or capacitors in series? Can follow a "rule" or a intuitive method? I have to do difficult exercises regarding system of capacitors ...
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2answers
67 views

Coefficients of capitance

In my syllabus about electromagnetism, they introduce the coefficients of capacitance by stating that, if we have $n$ conductors enclosed by linear dielectrics, then we can write 'because of ...
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1answer
200 views

What is the difference between a battery and a “polarized” charged capacitor?

I know that the main difference between the two is that a battery can provide a constant voltage whereas a capacitor's voltage decreases as the charge stored decreases. But what about the internal ...
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1answer
107 views

Field of a parallel plate capacitor

Pretty much in all the diagrams I have seen the electric field of the parallel plates is depicted as in this image The field lines seems to start bending only after leaving the periphery of the ...
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2answers
634 views

Calculate the electric potential energy stored in a capacitor [closed]

Calculate the electric potential energy stored in a capacitor that stores 3.40 x 10^-10 C of charge at 20.0v I am lost. I am scared.
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2answers
722 views

How does capacitors provide initial high voltage for a motor?

While observing the water pump in my house I could see a huge capacitor connected to it. My father told me that it is to provide a high voltage of 440 V during the start-up process. But, how does a ...
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1answer
78 views

In what way do passive circuit elements change the functional form of the voltage?

I heard capacitors affect the valleys and mounds of voltage sine curves, so that you get DC from AC. It's related to Graetz bridge, flipping signs of sine waves and seemingly afterwards smoothing ...
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1answer
151 views

Why do some capacitors leak and other capacitors hardly leak at all?

I just found out that electrolytic capacitors hardly leak whereas non-electrolytic capacitors leak and at times, leak a lot. Questions: (a) what causes capacitors to leak? (b) why do electrolytic ...
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1answer
129 views

Electric field and capacitance across a resistor

Using a simple lattice model of conduction, where electrons are accelerated by an electric field, and are slowed down by bumping into the lattice, you get the following equation for current density: ...
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2answers
403 views

Alternative derivation for the capacitor energy equation [closed]

I hope this is the right place for this kind of post. A friend is trying to derive the equation for the energy stored in a capacitor by analysing the change in potential on one plate when the ...
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5answers
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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 ...
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1answer
4k views

Does the phase difference between voltage and current in an LCR circuit exist throughout the circuit?

I know that in an purely inductive circuit the current lags behind voltage by $90^o$, in a purely capacitive circuit vice-versa and in an LCR circuit the current may lag or gain with respect to ...
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0answers
118 views

How is derived the relation between capacitances when a $Y-\Delta$ transformation is applied in a capacitors network?

A $Y-\Delta$ transformation can be applied to circuits in order to make an equivalent circuit (but simpler to put in terms of series/parallel devices). Wikipedia and other books show how to deduce the ...
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0answers
263 views

Calculating Electric Field from a Potential Difference w/o Charge

So here is my homework question: Two long cylindrical shells of metal (radii $r_1$ and $r_2$, $r_2 > r_1$) are arranged coaxially. The plates are maintained at the potential difference ...
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84 views

What is the electrical field of a capacitor plate as a charge approaches

The electrical field for a charge density $\varrho(r)$ is $${\bf E}({\bf r})=\frac{1}{4\pi\varepsilon_0}\int \varrho({\bf r}')\frac{{\bf r}-{\bf r}'}{\hspace{.1cm }|{\bf r}-{\bf r}'|^3} \mathrm ...
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1answer
2k views

Difference between voltage and potential energy in a capacitor

I'm confused about the difference between voltage and potential energy in a capacitor. Suppose you have a capacitor with a voltage V and capacitance C, and you release a particle with charge $+Q$ from ...
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1answer
92 views

combination of 5 identical capacitors [closed]

Given 5 identical capacitors, each EMF. Draw the proper combination of all these 5 capacitors.. 1.) 2.5 2.) 4.17 I really do not know how to solve this thing and if anyone of you knows the title of ...
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2answers
2k views

How capacitive is the human body?

Testing a capacitive screen, it's clear that it can tell the difference between a celery touching it (human holding it with an isolating material) and a human touching it. Touching it holding a ...
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3answers
166 views

Will the rms current be affected by inserting dielectric in the capacitor in an LCR circuit?

MY thoughts: I think it will not be as the expression for RMS value is dependent only on the peak value of current. Is my thinking correct?
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2answers
72 views

Capacitor's voltage

Imagine I have two plates that form a capacitor, so the magnitude of the charge in each plate is, let's say, $Q$. So, the force, in respect to the distance $d$, is gonna be: $$F(d) = ...
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1answer
236 views

Is this a series or parallel connection?

I am confused how the capacitors in this circuit are connected. $C_4$, $C_6$ and $C_5$, $C_3$ appear to be parallel, but both $C_4$ and $C_6$ seem to be in series with $C_1$ as do $C_5$ and $C_3$. Am ...
2
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1answer
348 views

$\pi/2$ phase shift in RC circuit

I just recently learnt Alternating Current and RCL circuits and I also learnt about phasers and various graphs. Now I also know that current lags in an LR circuit. My intuitive understanding of this ...
3
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2answers
182 views

Moving the plates of a charged capacitor to calculate energy density - where's the flaw in my argument?

For a charged air-dielectric capacitor, let the plates be parallel to the $xy$ plane, with the top carrying a positive charge $+Q$, the bottom a charge $-Q$. The force on an infinitesimal charge ...
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3answers
612 views

The moving capacitor

To what extent can a charged capacitor mounted on a moving platform (e.g. a rotating wheel) be considered an electric current generator? Electric current, after all, is nothing more than the transport ...