The ability of an object to store electric charge.

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RC Circuit Analysis

I want to correct three misunderstandings about the following RC circuit. 1) How does current move directly after switch S gets closed? Current runs through all three circuit components to begin ...
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0answers
24 views

Voltage between conductors in single phase line [on hold]

I am trying to understand capactiance between conductors in a single phase line, but I am stuck, I am following this ...
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1answer
26 views

How can I rearrange an equation to find a gradient for a capacitor?

If I plot R on the x axis and T on the y axis to give a straight line graph, and I am given that $V$ = $V_0$ * e^(-t/RC) then how can I prove that the gradient of the graph is equivalent to $C$ * ln3, ...
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1answer
32 views

What does an increased time constant of a capacitor do?

If a capacitor is being charged to any voltage, what effect would increasing the time constant have on it and if a graph of Charge Q/Time T was plotted to give a positive decreasing gradient, how ...
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1answer
27 views

Smoothing capacitor

Suppose a capacitor of capacitance $C$ is being used in a rectifier to smooth out the p.d. across a resistor of resistance $R$. What is the effect on the smoothing curve when the $R$ is lowered? The ...
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6answers
98 views

Why do we use capacitors when batteries can very well store charges?

Can batteries be used instead of capacitors? I am trying to figure out a basic, superficial and any obvious difference between the two.
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3answers
42 views

How does the voltage across an inductor and a capacitor vary in series LCR circuit about resonance?

I am aware that at resonance, the voltage across the inductor and the capacitor are equal in magnitude and opposite in phase. However, I want to know how the voltage across $L$ and $C$ vary if I vary ...
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1answer
35 views

what is the capacitance and inductance of an ideal wire?

I am reading a magazine for acoustics, one article is about the choice of speaker wire. The article said the ideal speaker wire should has no resistance, capacitance and inductance. I understand that ...
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1answer
14 views

Displacement vector in parallel plate capactor

This ought to be simple, but I'm running into some questions... Let's say we have a parallel plate cap with some linear homogeneous dielectric media between the plates. The plates are distance $a$ ...
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4answers
969 views

Does a capacitor ever get fully charged?

The time $t$ taken by a capacitor of capacitance $C$ in a charging circuit with a resistance $R$ in series with it to accumulate charge $q$ is given by the equation $$t = \tau ...
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0answers
39 views

Why is capacitance taught instead of elastance? [closed]

I am an AP physics C student and last year I took physics B (now called 1 & 2). We learned about resistors first, then capacitors which everyone failed because it was a bit rushed. Anyway, now ...
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1answer
50 views

Equivalent Capacitance [closed]

What is the equivalent capacitance between A and B?
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1answer
30 views

Potential Difference between 2 points in a curcuit

3 Cells and 3 capacitors are connected as shown in the diagram. What is the potential difference between points A and B ? What are the final charges on each of the plates of the Capacitor ? Does the ...
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1answer
24 views

Why do I different values compared to my theoretical time?

I'm having an experience about time needed to charge the capacitor to the 63.2% voltage of the batteries. There are resistance, capacitor and batteries in the circuit. When I calculate the ...
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1answer
34 views

Final charges on Capacitors connected in a curcuit

Capacitor C1 is charged to a Potential Difference of 10V. It's capacitance is 2 microFarad. Capacitor C2 is charged to a Potential Difference of 15V. It's capacitance is 4 microFarad. Now the ...
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1answer
25 views

What does “Receptor” convention refers to in RC circuits?

my question is How can we choose the convention in a circuit and what does it refer to ? Especially for a Capacitor I hear the terms "passive sign convention..." "receptor convention ..." "generator ...
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0answers
18 views

How to calculate the capacity of an electroscope out of the geometry and why is it independent on the pointer deflection?

How can one calculate the capacity of an elektroscope like the following from the geometry of the setup? How does this formula implies that the capacity does not (approximatly) depend on the ...
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2answers
35 views

Capacitor discharging

We know that discharge a capacitor will cause the voltage of capacitor to drop with time. But how about the bleeder resistor? Will the voltage of bleeder resistor increase or remain unchanged?
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2answers
24 views

Why is cap voltage negative in KVL for discharge circuit?

I was just trying to derive the equation for a capacitor discharging through a resistor, and I've run into in a problem. If I set up my KVL, then I would say $iR = V_c$ (where $i$ is instantaneous ...
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2answers
97 views

Why is there electric field OUTSIDE a battery?

Correct me if I'm wrong, but a battery's electric field is like an electric field of a capacitor consisting of two parallel plates. But we know that the electric field outside the two plates is zero. ...
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1answer
35 views

Image charges and capacitors?

Consider these two situations: A (infinite) parallel plate capacitor in which one plate is held at a potential $V$ and the other is grounded. A point charge near an infinite plane and grounded ...
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2answers
62 views

What stops charges from jumping across a capacitor?

I've learnt in class that charges store up on capacitor plates (the electrons). But why don't the electrons just jump across capacitor, what stops them? At first I thought perhaps it might just be the ...
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0answers
18 views

Designing a capacitor and electrical double layer capacitor

Hello! based on the image above, I am wondering if my assumptions are correct that i can make a capacitor using this design (1) and (2) are "infinitely" long layers (1) layer is made up of same ...
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0answers
18 views

Back force after capacitor is discharged

You have a mechanical hand crank generator connected to a capacitor. You charge the capacitor by cranking it (you obviously have a back current as you crank it so it is difficult to crank). At a ...
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1answer
26 views

Capacitive pressure gauge under a change of pressure

I have seen in an article, that a capacitive pressure gauge made of two parallel plates with a dielectric material between with constant $K$ under an increase of pressure $\Delta P$, a Young´s modulus ...
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1answer
34 views

What happens to the energy of a capacitor after a dielectric is inserted?

Consider a parallel plate capacitor having capacitance $ C$ and charge $Q$. then the energy of the capacitor will be $\frac{Q^2}{2C}$. Now if a dielectric is inserted, then $C $ increases and thus the ...
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1answer
63 views

Dielectric slab inserted into a constant voltage capacitor

I was told that a dielectric slab inserted into a capacitor connected to a battery (constant voltage) will be repelled, because the energy stored in the capacitor increases when the dielectric is ...
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3answers
35 views

Why capacitor pass AC and block DC current? [duplicate]

We know that in circuit capacitor block the DC current and pass AC current. My question is how a capacitor block DC and pass AC?
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1answer
35 views

Finding the current and voltage in a circuit with DC sources

I know that in a circuit with DC sources a capacitor(steady state) can be replaced with an open circuit and an inductor(steady state) can be replaced with a short circuit. My understanding is that ...
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1answer
111 views

Total Energy Stored in Seven Capacitors [closed]

The capacitive network shown in the figure is assembled with initially uncharged capacitors. A potential difference, Vab = +100V, is applied across the network. The switch S in the network is kept ...
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2answers
82 views

Using a charged capacitor to charge two others [closed]

Here is the homework question in question: The figure (below) displays a 13.1 V battery and three uncharged capacitors of capacitances C1 = 4.08 μF,C2 = 6.19 μF and C3 = 3.30 μF. The switch is thrown ...
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2answers
53 views

How do capacitors discharge?

I'm having some trouble understanding how capacitors work. I can visualize how a capacitor would charge up and how current "flows" through it. But I don't really understand the concept of the ...
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0answers
14 views

Current flow in a polarized capcitor

What is a polarized capacitor? I have learned that in a polarized capacitor, the negative lead must be connected to the negative terminal of the battery and so the positive. But my doubt is that if ...
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1answer
69 views

Why is the potential difference across these two capacitors both 9V?

So above are two difference circuits, each with a 9V battery and a capacitor of the same capacitance. $C_1=C_2$ Why is the potential difference across both capacitors 9V? Shouldn't it be less than ...
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3answers
36 views

Resistance of capacitors

Please I would like to know how the resistance of the plates of a capacitors work? Is it the same as a resistor? If yes, is there electric field inside the plates like inside a resistor?
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1answer
48 views

Why isn't this a valid derivation of the formula for capacitors in series?

I had to derive the formula for capacitors (I decided to use m capacitors in my derivation) in series, and this is what I did. The formula for a capacitor is $$Q=CV,$$ which is the same as saying ...
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1answer
161 views

Finding the voltage of the circuit?

Capacitor 3 in Figure (a) is a variable capacitor (its capacitance C3 can be varied). Figure (b) gives the electric potential V1 across capacitor 1 versus C3. The horizontal scale is set by C3s = 20 ...
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1answer
38 views

What is the positive charge in a capacitor made of?

A capacitor is a pair of conductors separated by an insulator. When it gets charged we have negative charges in one of the plates and positive charges in the other. Negative charges are electrons but ...
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1answer
22 views

Potential of 2 parallel plates

How can I write down a potential of 2 parallel plates (area $A$) with charge $+Q$, $-Q$ such that V(inf)=0 and V(in) is what I would expect, $Ed = Qd/A\epsilon_0$. Do I have to write a discontinuous ...
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2answers
111 views

Capacitance and voltage drops

Let's say that Switch $S$ is closed. I have a conceptual question: If a stream of particles acquire a potential difference upon exiting the battery, why will they lose some of that potential ...
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3answers
58 views

Current in an RC Circuit

If an $emf$ leaves from point A, the concepts at play in the following diagram are straightforward: at any time, the $I_{R}$ = $I_{c}$ as time increases, $\Delta V$ across $R$ decreases and it ...
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3answers
135 views

(Capacitance of a battery?) Finding the charge accumulated on a rod

We all know the expression for the potential difference across a conducting rod moving through a region with a uniform magnetic field: $\epsilon = B l v$ Now my question is different. Is it ...
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1answer
145 views

The advantages of a dielectric in a capacitor

In a capacitor a dielectric can be placed in between the two plates. I have trouble understanding the points / advantages of a dielectric from what I have read in a text book. The points written there ...
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1answer
59 views

Why is there current in LC Circuits?

When we connect two electric sources (positive to positive and negative to negative) then the current that runs the circuit is calculated as follows: $ I = (E1-E2)/(2r + R) $ In case of an LC ...
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2answers
111 views

Both plates of capacitor have positive voltage

If both the plates of a capacitor are connected to positive voltage (say, one is +10V and the other is +5V), but there is a voltage difference between the plates, will the capacitor be charged? And ...
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1answer
51 views

Current in a fluorescent tube that is not in a circuit

In Walter Lewin's 8.02 Electricity and Magnetism course, he places a fluorescent tube pointing radially outwards from a large Van der Graaf (VDG) generator. Due to the VDG's E-field, this causes a ...
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0answers
15 views

Capacitance and grouping of capacitors [duplicate]

What happens when positve end of a capacitor is joined with negative end of another capacitor. Will there would be charge flow.
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1answer
104 views

charge distribution on three conducting plates [closed]

There are three parallel plates identical and equidistant. A charge q is given to the first plate.And then the second and third plate are connected with wire.Then how to find its charge distribution. ...
0
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0answers
40 views

Can Van Allen Radiation belts act as a capacitor?

There are two Van Allen Belts at rougly 5000Km and 17000Km from the surface of the Earth each of them containing majority of one of the charges electrons and protons). Can these belts like a ...
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1answer
62 views

charged dieletric/conductor in capacitor

It is a standard problem to consider a dielectric or a conductor between the parallel plates of a capacitor. But what happens to capacity, voltage, charge, inserting between the plates of an ideal ...