Tagged Questions

The ability of an object to store electric charge.

67 views

Explaining why there is current in a circuit with a capacitor whilst the capacitor is charging

The question I'm trying to answer is part b) of the question below: My answer was: As some of the electrons will initially be repelled by the electric field of the negative plate, there will be ...
85 views

Voltage drop across capacitors in series, why?

Basically when you connect more than 1 capacitor in series then the charge on each capacitor is same but there is a voltage drop across each capacitor. I have no intuition as to why the voltage drop ...
35 views

Capacitors in an AC circuit

Can I combine capacitors in the same way for an AC circuit as I can for a DC circuit (In series or in parallel)? Does the same apply for simplifying resistors?
110 views

RC circuit energy [closed]

I am quite new at circuit analysis and I have a question about a RC circuit, with the resistor and the capacitor connected in series. I want to find the energy supplied by the ideal voltage source ...
35 views

How does a capacitor pass the flow?

Capacitor has just two conductor surfaces which have no touch. How can it pass the electric flow when there's no touch between the surfaces?
36 views

Deriving the charge as a function of time in a discharging capacitor

There is obviously something I have not understood well. In Kirchoff's second law, we take the potential difference of batteries and capacitors with the sign that we traverse it. So, let's assume that ...
107 views

Electric field between 2 parallel plates

The question state that 2 large parallel plates are a distance $d$ apart and the field at $d/2$ is $E$ if the distance between the plates are reduced to $\frac{d}{2}$ what is the field strength ...
37 views

LCR circuit at resonance

I am studying about the LCR circuit and have a question regarding potential difference across inductor and capacitor. From the thing I have studied I came to know about that potential across inductor ...
34 views

Equivalence between voltage drop across capacitors and resistors?

In simulating a circuit, comprised of 2 capacitors of same size but different dielectrics, their capacitance ratio ${C1}/{C2} = \epsilon2/\epsilon1$. Problem is, in finite element programs, I am ...
27 views

Physics of the capacitance of an electrolytic capacitor

In explanations about the electrolytic capacitor one often cites the formula $$C = \epsilon_r \epsilon_0 \frac{A}{d}$$ for the capacitance $C$. Then one says that by enlarging the area $A$ via ...
133 views

Putting a capacitor into a strong magnetic field, will this change the capacity?

I'm wondering, does a magnetic field change the number of electrons, placed and displaced on the two plates of a capacitor. To prove or disprove this, I think the capacitor could be connected to an ...
22 views

Triphasor Problem

Given the data presented in the following link I have to get $R$ for $P = 90~\textrm{kW}$ and the line currents $i_1$, $i_2$ and $i_3$. Any ideas?
51 views

Equivalent DC circuit with charged conductors

I am trying to find equivalent circuit for a circuit composed of interconnected capacitors when isolated pieces of conductor may carry nonzero electric charge, and I have been struggling with this ...
67 views

Self capacitance

I have two spheres of metal, each of radius $1m$, these spheres are effectively an infinite distance apart. I now connect a $1V$ power supply between these two spheres: (and wait an infinite amount ...
30 views

How Calculate the electric field into capacitor [closed]

Hello i have a problem with this exercise with capacitor, I have to calculate the electric field between the capacitor plates (neglecting the edge effects ), but I do not know how to do Text: A plate ...
36 views

Capacitance of Nested Spheres

Imagine that we have two nested spheres and I wish to calculate the capacitance. First of all, I'm able to do the calculation. What I'm confused about is how it is possible for the Electric Field to ...
240 views

How the voltage of a capacitor is changed in charging/discharging [closed]

Capacitors are called fast batteries in electronics. I understand that a battery is charged by a constant current while the voltage is almost constant during charging and discharging. For example, a ...
42 views

How does a capacitor get charged while the charger circuit isn't closed? [closed]

a capacitor is a very known device in circuits that can be used as a short-time battery by charging it using another source, but how does it really get charged? if the plates of the capacitor don't ...
50 views

How is energy really lost due to heating in charging a capacitor?

Wanted to be sure, where is this understanding wrong? If a capacitor is charged to a potential difference $V$, then $Q$ in the capacitor would be $CV$. Now if we assume the voltage of the power ...
163 views

Non-parallel plate capacitor's capacitance [closed]

So far, I fully understood how to find the capacitance of a parallel plate capacitor. However, for the case of non-parallel plate one, how one could solve that kind of problem knowing that one plate ...
49 views

Differences between isolated parallel plate capacitors and parallel plate capacitors with a battery attached?

I think I get the general idea with what the difference is, which is that the battery creates a constant potential difference between the plates since the charge stays the same. I know that an ...
54 views

Why is it that when potential difference across a capacitor is equal to the supply voltage, no flow occurs?

Can someone explain to me how and why this happens? I'm really confused. I'm also confused about how the net charge between 2 plates is 0.
45 views

No change in voltage in a capacitor

While trying to solve this question: Photo copy of the question and answer: Question:On charging a parallel plate capacitor to potential V the spacing between the plates is halved and a dielectric ...
101 views

A capacitor with a conductor between the plates [closed]

Consider a parallel plate capacitor of area $A$ with a distance between the plates $d$, disconnected from the battery. I wonder, how would the capacitance of the system change if we placed a conductor ...
25 views

Charge in capacitor after switching voltage

Say you have a capacitor connected to a voltage source (vs). After the capacitor has fully charged, you cut the source voltage in half to vs/2. The voltage across the capacitor should change to match ...
85 views

Circuit with three capacitors

A potential difference of V = 38.0 V is applied across a circuit with capacitances C1 = 4.1 nF, C2 = 4.7 nF, and C3= 2.3 nF, as shown in the figure. What is the magnitude and sign of q3l, the ...
128 views

Definition of equivalent capacitance

I know that equivalent capacitance of multiple capacitors in series is $$C = \left(\frac{1}{C_1} + \cdots + \frac{1}{C_n}\right)^{-1}$$ and in parallel is $$C = C_1 + \cdots + C_n.$$ But there are ...
106 views

Capacitors and external electric fields

I am grading questions from the lab manual provided by the professor to review with the students. I am trying to wrap my head around one of the questions about what an external electric field would ...
390 views

How is Capacitance affected by a seperation distance and with or without a battery?

The questions specifically says this : A parallel-plate capacitor initially has capacitance $C$. The distance between the plates is then doubled, with a $9.0V$ battery connected. The battery is then ...
82 views

The separation between the two plates of a capacitor is increased

I had the following question on a quiz recently: A capacitor consisting of two parallel plates, separated by a distance $d$, is connected to a battery of EMF ε. What happens if the separation is ...
109 views

Proving charge on outer surface of parallel plate capacitor must be zero

If we have two conducting plates, with charge $Q$ and $-Q$, why is the charge on the outer surfaces of each conductor zero? I've been trying to wrap my head around the problem. Firstly, don't excess ...
38 views

Quality factor of an LCR circuit

The quality factor of an LCR circuit is defined as: $$\omega°/2\delta\omega$$ $\omega°$ stands for the resonant frequency, and $\delta\omega$ for the range of frequencies between half power point and ...
25 views

Capacitor charge and current as a function of type question [closed]

Two capacitors, one resistor and an ideal battery are connected through switches s1,s2 and s3 as shown in figure. Initially capacitor of capacitance 4C is charged, while other is uncharged. The upper ...
149 views

Understanding parallel plate capacitors [closed]

I need help with understanding this assignment. I originally though of using the equation of Eo*A/D = Q/ΔV but I don't know how to answer this without actual numbers to plug in besides the epsilon-not ...
64 views

Help to solve a circuit with capacitor and resistor

Till now I'd never solved a circuit with resistor and capacitor. I'd seen the problem and tried to solve. But now I am in a doubt.The circuit was like that- My attempt-
47 views

Determining initial voltage across a capacitor [closed]

This one has got me stumped. I have a graph of voltage vs time and a corresponding power vs time graph. Taking the integral of the power vs time graph gives me the work done on the capacitor. Now the ...
50 views

Potential across the plate of a capacitor

So I came across this question: Two capacitors are connected in series of given capacitance $5\ \mu\mathrm F$ and $10\ \mu\mathrm F$. The first plate of the $5\ \mu\mathrm F$ capacitor is given a ...
68 views

Sign of induced EMF and other elements in AC circuit

I am having problems to determine the direction of the induced EMF in AC circuits. For example, we have an inductor of inductance $L$. The induced EMF is given by: $$\epsilon = - L \frac{di}{dt}$$ ...
77 views

How do two metal balls of radius $r$ kept at a large distance form a capacitor? [closed]

So this is something really new to me. I have learnt of plate capacitors, cylindrical capacitors, single spherical capacitors, etc. but that to, of finite distance between them. Also please explain if ...
121 views

Electric flux density between the 2 plates of a capacitor

I am reading a solved exercise about a parallel plate capacitor in which states that the electric flux density between the 2 plates is: $$D=p_{s}$$ where $p_{s}$ is the surface current density of ...
59 views

Problem with differential equation RLC circuit serie [closed]

I am trying solve the differential equation of RLC's circuit in serie, I have: $C=4\ F, L= 1\ H$, $R=5\ \Omega$, and $V_e=20\ V$. $1)$ first I got the equation, it is: $i''+5i'+\frac{1}{4}i=0$, what ...
42 views

Displacement current in a capacitor

I recently learned about the concept of displacement current in a capacitor. I've understood the basics - mainly understood the reason why it was introduced. However, is it purely a mathematical ...
138 views

Capacitance of two non parallel plates with two dielectric materials

There is one answered question about the two non parallel plate capacitance here. However, it only has one dielectric material. I am looking for a formulae of the same configuration, but with 2 ...
28 views

Capacitor connected across two isolated sources [duplicate]

Lets say there are two isolated sources of positive charges $q_1$ and $q_2$ $(q_1>q_2)$ located sufficiently far apart. If the two are connected to the two plates of a capacitor, then what is the ...
97 views

RC circuit discharging capacitor, trouble understanding

If we apply loop rule while charging the circuit we get: $$\varepsilon -iR-\frac{q}{C}=0$$ The way I understand, we follow trough the circuit just before the battery, as we move trough the circuit ...
82 views

What is capacitance, in general?

In circuit analysis software capacitance can be measured between any two nodes of a circuit or of a multiterminal device. In practical terms we take $C_{ij}$, the capacitance between $i$ and $j$ as ...
30 views

Is it possible to make a capacitor of required specifications using aluminium foil? [closed]

I wanted to make a FM radio transmitter but I was not able to get a capacitor with the exact rating of certain micro farad and pF. But I live in a poor country and I can not find them in the local ...
70 views

E field of parallel plates with metal inside

I was asked to determine the electric field in the spaces between the copper bar and the plates. The voltage across the plates was 30 V, so naturally I’d use $E=\Delta V/d$ to determine the field. ...
Suppose we have the following circuit: Such that for $t<0$ the switch M was open. If we close the switch at $t=0$ what will the voltage on the capacitor, $V_C$, be at $t=0^+$? What about \$\dot ...