Conversation with Merlin [email protected] · Tue Dec 12 2023

I want you to analyze these two images. One diagram is a spherical capacitor consisting of positive charge near the centre, and negative charge at the edge. This spherical capacitor is made out of two dielectrics layered one after another (ie. first layer near the centre of the sphere and second layer closer to the edge. Permittivity of dielectric 1 = epsilon 1, permittivity of dielectric 2 = epsilon 2), then explain how the electric field and flux density would behave moving radially outwards from the center. Explain with as much detail as possible, and give physical reasons for the behaviour of the electric field too. Also compare the magnitudes of the electric field in each dielectric and also at their conjunction

To analyze the behavior of the electric field ((E)) and flux density (()) in a spherical capacitor with two dielectric layers, we must refer to Gauss's law and the continuity of electric displacement field at the interface between two dierics.

For a spherical capacitor:

  1. The electric field (E) due to a spherical charge distribution is radially outward (or inward for negative charge) and varies inversely with the square of the radius (r), because of the symmetry involved. Mathematically, it's given by:

    (E = \frac{}{4\pi\epsilon}\frac{Q}{r^2),

    where (\epsilon) is the permittivity of the medium, (Q) is the enclosed charge, and (r) is the distance from the center.

  2. The electric flux density (D) is the product of the permittivity of the material and the electric field,

    (D = \epsilon E).

Moving radially outwards from the center of the spherical capacitor:

  • In the First Dielectric Layer (near center, ( \epsilon_1 )): The electric field (E_1) decreases with (^2). As you move away from the central charge, the flux must pass through a larger spherical surface area, since the area of a sphere is (4\pi r^2). Since the flux is spread over a larger area, the field weakens.

    The electric flux density (D_1) this region will be ( \epsilon_1 E_1 ).

  • At the Between Dielectric 1 and Dielectric 2:

    At the boundary, the normal component of the electric displacement field (D) is continuous due to the absence of any free surface charge, which means:

    ( \epsilon_1 E_1 = \epsilon_2 E_2 \ Therefore, even if the electric field magnitude differs because of different permittivities, the product of (E) and (\epsilon) must be the same across boundary to satisfy continuity.

  • In the Second Dielectric Layer (closer to the edge, ( \epsilon_2 )):

    The electric field (E_2) to decrease with (r^2), and the electric flux density (D2) in this region will now be ( \epsilon_2 E_2 ).

    Since theittivity (\epsilon) affects how strongly the material becomesized in an external electric field, the electric field magnitude (E_2) will adjust to maintain the continuity of (D). If (\epsilon_2>\epsilon1), then (E_2<E_1) in such a way that (D remains constant, as (D = \epsilon E).

Comparing the Magnitudes:

  • Electric Field:

If (\epsilon_2 > \epsilon_1), (E_2) at the junction (interface) must be less than (E_1) maintain the continuity of (D). This is due to the material's ability toize more strongly, effectively reducing the local electric field strength.

  • Flux Density:

    (D) will continue to decrease as (r) due to the expanding spherical surface but will remain continuous across the boundary of the twolectrics.

In summary, moving radially from the center to the edge of a spherical capacitor:

  • The electric field and flux density decrease with (r^2- At the interface of two dielectrics with different permittivities, the electric field magnitude adjusts to ensure continuous displacement field (D).
  • The material with a higher permittivity will have a lower electric field magnitude at the interface due to its increased ability to polarize.

Physically, these behaviors are due to the spherical symmetry of the charge distribution and the nature of the dielectric materials responding to an applied electric field. The higher permittivity indicates a greater ability to align dipoles within the dielectric material, reducing the net electric field within it.

%PDF-1.5 % 3300 0 obj<>stream x]%7nJZ/` \z;d<RGS 4UY:6 iP7bDZ*>Q}k-Ql -qDkIFdc/jDoFK1eQ|L5K)Yl=bIbzIGInjU)&ma 2fm~M1v6n{1*JHy5-UBbTNhT5\]m:Zhfe6G`lAjN[lcEK,F$>.;U2fo[j#LHF(]Gi]GM]G5/:F:r nls4Q)8|h^W5[#Tq:$funVUb1k, roEE@08e:79es *k!;u1Tvqt05gqLZ QnU9mhp >H1D H4^G)a[aTq e&hq#{GbvGbvJrUi.y8:sul(5QTw)d*mF*V6,pLG/*vG{)\qUKq82\staq<MQ&Z3Jr&sIq4U&FU|MuIv4Y0)S{fS9\#gepbhh6b?gbg&3z[>tTsyA|-gRgzFo-5Kq23[Le:l?t*:2#l6~two>^xig~6_L'[nwI$a=cFDlW,MB B ""\m nhhv 0,`O@E@ P0L 5{ W\ FHHL! D-%@+a+^ {ekTP3gZAB $XVYqfHV|Xa]K'T$d}ws?^N"A(D(SiZjcy:dD ; Dqh* vEWXJ@+Q?D\! W$ VD! UI$lQH y bU&2Y*g)DSfs_WX )M^M9`# 62aI []`C p@"r3)7 $2@I`3h8Hxq.hWt)P0*R(Q D)RII2JQd0#aF 3f$Hd= {$_a % K N'P"0M*D$B&3DLQ*k+ !DHDJ$"93Rx !Q@RX EV9U,ndq# YnATd"E>\,\d" 'xCUevcF4H&0X>dHGRJ$Dv!.IZ0B B8*xUt c8S3H"WSDv9 1%_ ^`!..)%$ 2D$uB`57DRgffmbs+#6H {C0/]Epuv\11=,.A`|dp3zppGb[(jY"!@ P8#.@w~Gn{a0kJ/c](@L9RC.R  {)XHa/R[] `+2v F.e)$ ~@a~TBe.TR@P@N  PW6eR %PKY(R_ _2 6( _%*|` _(^(mBa'Ge@IM v];~VE; }a&H  r\9Sf'p#`Q D.-.<1? oXq;nQRnFnF8U\u_!$D"$V"%0@K-c Q2RBnc.W0]$(:)# nx6pe R AH\JYHJ .@ ]@=R}E pl#"UFV *T.d?!M Q&aJ[TmBYzB>a',(*  r  reZ#`'2;]0!D!,FaaNO$D@"7hB R-@!d^ S` &lh %@A6dM "P@]u / .:7#HVT@&hzVX ]SF X  6yi2')mFj.kcm:M6UjSm:M?mgkqf:B[-Rss3h:C#)N6baAUACHf rTE+qp tl4lnqEFFFFcV:q EoYf0qBD)M'e3 MeRVz210^uWUzq6T_z^{N&++Z*:*26&3~<?s9+as\G3zt -Kp@'a t4$p@OAKsbxk@D@T%O"!9!9!9!9!9!9!9!9!9!YHV$+dE :c^gsBk3ubRgu:tW~O0~$_}uVKK?MgZ97{W>MTtyF_~p+Bc4xEg%hm-B6c-[S=|9mLlSm,>2u{4}- %~%y}0nmHi7z#2rI1a99}Q 7g"xh[GF-g>[g+rhHy[>pni?O%8xx8a7}:1^"cO91k[^Wag-g{iNDf <xr)}Y9\&%>1n|CfK]|6E7fr,R=8llrp|<g/.z/.fzb\m|cz\9g._? .g_ctz_o~{^^BgGyASWm_WQ@n_:[%|(/&u1.B}Nd5g=g\Y UQRE0<q(s >WX|8y .]aV~.^mEyN}]'DV2KdGw~^3nK`} `7W]x%_>fumZ2v \_}IR%{4 +Q^f@eP /)5J3c};Ow'gw!BLxZ6zUS{fg97t_7`8?yYteibVS8zhmk:W=eKrlx<6<cY}CGrV/Peho>5+<(Y\w9'zkqp6Lo 8rp#lt;wt&{BWV;YA.3I9,4Ok66G wq3_soZn/|J}9apj~0Y p ON3'kg5xd{ :8 8_=94~kow:1D?:[*?7]>[N.~,~x|z 1W~!1 )"hQu+vre%7y!\ D2/qD(A?Lgp9Jsg--1>zx}l!Sj>G_>^w/ endstream endobj 3301 0 obj<>stream xZ]o+oM.nC}!)W]#Kj R1%X#gz#B0MdbR W59?h] F GYb2JL+j+ 4, )c. D r$gK}8dQ<bgC@8]hp!' `}(. "+E3b| %Cm/( JS#wfBI0P7:f @m6\X8p&$&THk.?g;,c&Z0d H[ Q@. `W0@ 9~1':#c(g$X 8xFUQ;RJJN5p'jJ)E@rF$XM@2r8In'H(%AbXM [-rem q19 +Vb|90_jwL.|93_YdH ,X@W5 de.p\Vq8 yQ`s+b7QNl;B\`*r`i;\V*-0-!J(.ab@APX`AaZ w52HFA',KZ }BW>|' $~( 5JBNH+`T`2 D0:jHf"jH0(( )f{ef GOP- Z1(RhuHTrbrc&[fl 2Ere>*NS C@1Za&R"<t.|wo?0?r#Up~ KH!7\11qE}w?>qmE(e&U]gxyU?~VZX;^%&]?*sx u iy[Z/>l<7B9c3DA^'D J1J (2l_^~>(^nR~Uc.ccGn:n4]B d qlHap!ypyzyE>@FOn+j^sy H~\u%CV"?I=_y/mr&K}ZC}}udI6cM W' EGBjK`l*K2L6Vo+kx %~> W_q~2^&'NMCD qr88\u&nO!W CoZc?;JmL zl[g0*?Twk v}~b %Rd1< 2bI.&ocm\b.ch_2C'JG9|^'nV!`l+Z_gRUx-(H7b`;D#0i{]7&d/a5 ?W0-Y{D':`SRv{vd>UB[.|x8J1yb/ee^lJzy?Sf~/!f4+!qz;5r?qJJ}IZ[.U]6#_N[vm]SkP0z]Z]_`kyoz~[Nbg/;VYw3} ;Djo@mkz.:>[?msx{WM\i@h'iR6N &>p #S&~ekQg{[Gl+oD!X<vXq0DdE6 [#M k5k/4!XVN~+H>[A-iZV5#]GgF6#T5 t-f`%`P7w(_ :{:zNs F ]^Lk04NH* oT}W+p]y5/}5/a~#;]8Ue,n {{>o:ZCe]V2PrtWyks]PvO^u?X~Z>[XYx:S;0Uw;4H^+N `}y^xK FuasMy;{tGJ2y 10Fy"?!t>{~l37K ; 0c+RG endstream endobj 3302 0 obj<>stream x[[o\ + h$vM #.~9gw{r38P9@1[U%z`(1$&6 ErMJ Y1v)D -,JHC+^(t/ LJdPNZnR[-:XMIWaL`p:%Y%%*GRWP-65sU{Um=@U]SR(gRE_HQ %#"8)&PZs:joQu:( 7

web.mit.edu

Are cylindrical and spherical E-field thrusters violating Newtons 3rd law?disproved analysis based on the classical model The following demonstration was the first attempt to analyze the electrostatic forces in cylindrical coaxial- and spherical capacitors with two different dielectrics between the electrodes, based on the classical understanding and accepted basic correlations. The measurements however, disproved the results of this analysis, and it is presented here only to demonstrate the consequences of the classical model that leads to contradiction and wrong results. The related measurements and the correct analysis with newly discovered laws are presented on the page semicharge.htm . Please note again that the analysis below is not correct because the basic F=qE formula is not applicable here! Previously we have discussed the force components of the electrostatic pressure acting on the surface of the conductive electrodes. However, in the presence of dielectrics two additional dielectrophoretic force components appear that act on the dielectric material. One of these dielectrophoretic force components that appear at the edges of the capacitor due to arced, inhomogeneous E-field lines has been discussed under dielectrophoretic pumps and we can call them edge-effect (EE) forces. The other dielectrophoretic force component will be described below. In fig. 5a. of the tutorial page about dielectrics it is shown that a dielectrophoretic force will attract the elementary dipoles of the dielectrics molecules towards the greater E-field intensity. The shape of the E-field between the electrodes of semi-cylindrical and hemispherical thrusters is inhomogeneous and converging towards the smaller electrode, where it reaches its maximum. Consequently the mentioned dielectrophoretic force will push the molecules of the dielectric towards the higher E-field intensity i.e. towards the smaller electrode. To differentiate this force component from the earlier discussed edge-effect force we can call it convergent-field effect (CFE) force, although basically both types are dielectrophoretic forces. CFE force of the semi-cylindrical thruster Let us calculate the magnitude of the resultant force component in the y direction, originating from these dielectrophoretic forces acting on the dielectric only between the electrodes. To accomplish this task we will have to know the attracting and repelling Coulomb forces upon the positive and negative charges of the elementary dipoles. Then by summing up these two opposing forces we get the resultant force upon the dipole. By integrating the elementary force components in the y direction over the whole volume of the dielectric, the macroscopic resultant force will be obtained. To perform these calculations, we have to know the magnitude of the equivalent dipole dp of an infinitesimal volume of polarized dielectric dV as the function of the local E-field intensity. In the case of linear isotropic dielectrics this is calculated as below: The electric polarization represents the density of dipoles per volume (where: n number of dipoles; V volume; N density of dipoles; p- elementary dipole). We get the correlation between P and E as: The dipole moment of an infinitesimal volume of dielectric is: Now we can calculate the resultant Coulomb force upon a dipole (fig. 10). Fig. 10. The E-field intensity between the electrodes of a cylindrical capacitor is: However this represents the total E-field at a certain point within the dielectric that is the sum of the E-field component created by the examined dipole (molecule) and the E-field components created by all the other dipoles (molecules) and free charges farther away from the examined dipole. If we want to calculate the Coulomb forces upon the examined dipole at this point with the formula F=qEeff (according to the established scientific understanding) then the effective E-field intensity in this formula should not include the self-generated E-field comp

rimstar.org

Learning ObjectivesBy the end of this section, you will be able to: Explain the concepts of a capacitor and its capacitance Describe how to evaluate the capacitance of a system of conductors A capacitor is a device used to store electrical charge and electrical energy. Capacitors are generally with two electrical conductors separated by a distance. (Note that such electrical conductors are sometimes referred to as electrodes, but more correctly, they are capacitor plates.) The space between capacitors may simply be a vacuum, and, in that case, a capacitor is then known as a vacuum capacitor. However, the space is usually filled with an insulating material known as a dielectric. (You will learn more about dielectrics in the sections on dielectrics later in this chapter.) The amount of storage in a capacitor is determined by a property called capacitance, which you will learn more about a bit later in this section. Capacitors have applications ranging from filtering static from radio reception to energy storage in heart defibrillators. Typically, commercial capacitors have two conducting parts close to one another but not touching, such as those in Figure 8.2. Most of the time, a dielectric is used between the two plates. When battery terminals are connected to an initially uncharged capacitor, the battery potential moves a small amount of charge of magnitude Q from the positive plate to the negative plate. The capacitor remains neutral overall, but with charges and residing on opposite plates. Figure 8.2 Both capacitors shown here were initially uncharged before being connected to a battery. They now have charges of and (respectively) on their plates. (a) A parallel-plate capacitor consists of two plates of opposite charge with area A separated by distance d. (b) A rolled capacitor has a dielectric material between its two conducting sheets (plates). A system composed of two identical parallel-conducting plates separated by a distance is called a parallel-plate capacitor (Figure 8.3). The magnitude of the electrical field in the space between the parallel plates is , where denotes the surface charge density on one plate (recall that is the charge Q per the surface area A). Thus, the magnitude of the field is directly proportional to Q. Figure 8.3 The charge separation in a capacitor shows that the charges remain on the surfaces of the capacitor plates. Electrical field lines in a parallel-plate capacitor begin with positive charges and end with negative charges. The magnitude of the electrical field in the space between the plates is in direct proportion to the amount of charge on the capacitor. Capacitors with different physical characteristics (such as shape and size of their plates) store different amounts of charge for the same applied voltage V across their plates. The capacitance C of a capacitor is defined as the ratio of the maximum charge Q that can be stored in a capacitor to the applied voltage V across its plates. In other words, capacitance is the largest amount of charge per volt that can be stored on the device: The SI unit of capacitance is the farad (F), named after Michael Faraday (17911867). Since capacitance is the charge per unit voltage, one farad is one coulomb per one volt, or By definition, a 1.0-F capacitor is able to store 1.0 C of charge (a very large amount of charge) when the potential difference between its plates is only 1.0 V. One farad is therefore a very large capacitance. Typical capacitance values range from picofarads to millifarads , which also includes microfarads (). Capacitors can be produced in various shapes and sizes (Figure 8.4). Figure 8.4 These are some typical capacitors used in electronic devices. A capacitors size is not necessarily related to its capacitance value. (credit: Windell Oskay) Calculation of Capacitance We can calculate the capacitance of a pair of conductors with the standard approach that follows. Problem-Solving Strategy Calculating Capacitance Assume that the c

openstax.org