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  239. 

  240. <div id="content">

  241. <header>

  242. <h1 class="title">

  243. <a href="./index.html" class="homepage-link">Pre-Quantum Electrodynamics</a>

  244. </h1>

  245. </header>

  246. <nav id="collapsed-table-of-contents">

  247. <details>

  248. <summary>

  249. Table of contents

  250. </summary>

  251. <ul>

  252. <li>

  253. 

  254. <details>

  255. <summary>

  256. <a href="./in.html#in">Introduction</a><span class="headline-id">in</span>

  257. 

  258. 

  259. </summary>

  260. <ul>

  261. <li>

  262. <a href="./in_p.html#in_p">Preface</a><span class="headline-id">in.p</span>

  263. 

  264. </li>

  265. <li>

  266. 

  267. <details>

  268. <summary>

  269. <a href="./in_t.html#in_t">Tips for the reader</a><span class="headline-id">in.t</span>

  270. 

  271. 

  272. </summary>

  273. <ul>

  274. <li>

  275. <a href="./in_t_l.html#in_t_l">Section and equation labelling</a><span class="headline-id">in.t.l</span>

  276. 

  277. </li>

  278. <li>

  279. <a href="./in_t_c.html#in_t_c">Contextual colors</a><span class="headline-id">in.t.c</span>

  280. 

  281. </li>

  282. 

  283. </ul>

  284. </details>

  285. </li>

  286. 

  287. </ul>

  288. </details>

  289. </li>

  290. <li>

  291. 

  292. <details open="">

  293. <summary class="toc-open">

  294. <a href="./ems.html#ems">Electromagnetostatics</a><span class="headline-id">ems</span>

  295. 

  296. 

  297. </summary>

  298. <ul>

  299. <li>

  300. 

  301. <details>

  302. <summary>

  303. <a href="./ems_es.html#ems_es">Electrostatics</a><span class="headline-id">ems.es</span>

  304. 

  305. 

  306. </summary>

  307. <ul>

  308. <li>

  309. 

  310. <details>

  311. <summary>

  312. <a href="./ems_es_ec.html#ems_es_ec">Electric Charge</a><span class="headline-id">ems.es.ec</span>

  313. 

  314. 

  315. </summary>

  316. <ul>

  317. <li>

  318. <a href="./ems_es_ec_b.html#ems_es_ec_b">Basics</a><span class="headline-id">ems.es.ec.b</span>

  319. 

  320. </li>

  321. <li>

  322. <a href="./ems_es_ec_c.html#ems_es_ec_c">Conservation</a><span class="headline-id">ems.es.ec.c</span>

  323. 

  324. </li>

  325. <li>

  326. <a href="./ems_es_ec_q.html#ems_es_ec_q">Quantization</a><span class="headline-id">ems.es.ec.q</span>

  327. 

  328. </li>

  329. <li>

  330. <a href="./ems_es_ec_s.html#ems_es_ec_s">Structure</a><span class="headline-id">ems.es.ec.s</span>

  331. 

  332. </li>

  333. 

  334. </ul>

  335. </details>

  336. </li>

  337. <li>

  338. 

  339. <details>

  340. <summary>

  341. <a href="./ems_es_efo.html#ems_es_efo">Electric Force and Energy</a><span class="headline-id">ems.es.efo</span>

  342. 

  343. 

  344. </summary>

  345. <ul>

  346. <li>

  347. <a href="./ems_es_efo_cl.html#ems_es_efo_cl">Coulomb's Law</a><span class="headline-id">ems.es.efo.cl</span>

  348. 

  349. </li>

  350. <li>

  351. <a href="./ems_es_efo_ps.html#ems_es_efo_ps">Principle of Superposition</a><span class="headline-id">ems.es.efo.ps</span>

  352. 

  353. </li>

  354. <li>

  355. <a href="./ems_es_efo_exp.html#ems_es_efo_exp">Experimental Investigations</a><span class="headline-id">ems.es.efo.exp</span>

  356. 

  357. </li>

  358. <li>

  359. <a href="./ems_es_efo_e.html#ems_es_efo_e">Energy in Systems of Point Charges</a><span class="headline-id">ems.es.efo.e</span>

  360. 

  361. </li>

  362. 

  363. </ul>

  364. </details>

  365. </li>

  366. <li>

  367. 

  368. <details>

  369. <summary>

  370. <a href="./ems_es_ef.html#ems_es_ef">Electrostatic Fields</a><span class="headline-id">ems.es.ef</span>

  371. 

  372. 

  373. </summary>

  374. <ul>

  375. <li>

  376. <a href="./ems_es_ef_pc.html#ems_es_ef_pc">Electrostatic Field of Point Charges</a><span class="headline-id">ems.es.ef.pc</span>

  377. 

  378. </li>

  379. <li>

  380. <a href="./ems_es_ef_ccd.html#ems_es_ef_ccd">Electrostatic Field of Continuous Charge Distributions</a><span class="headline-id">ems.es.ef.ccd</span>

  381. 

  382. </li>

  383. <li>

  384. <a href="./ems_es_ef_cE.html#ems_es_ef_cE">The Curl of \({\bf E}\)</a><span class="headline-id">ems.es.ef.cE</span>

  385. 

  386. </li>

  387. <li>

  388. <a href="./ems_es_ef_Gl.html#ems_es_ef_Gl">Gauss's Law: the divergence of \({\bf E}\)</a><span class="headline-id">ems.es.ef.Gl</span>

  389. 

  390. </li>

  391. 

  392. </ul>

  393. </details>

  394. </li>

  395. <li>

  396. 

  397. <details>

  398. <summary>

  399. <a href="./ems_es_ep.html#ems_es_ep">The Electrostatic Potential</a><span class="headline-id">ems.es.ep</span>

  400. 

  401. 

  402. </summary>

  403. <ul>

  404. <li>

  405. <a href="./ems_es_ep_d.html#ems_es_ep_d">Definition</a><span class="headline-id">ems.es.ep.d</span>

  406. 

  407. </li>

  408. <li>

  409. <a href="./ems_es_ep_fp.html#ems_es_ep_fp">Field in terms of the potential</a><span class="headline-id">ems.es.ep.fp</span>

  410. 

  411. </li>

  412. <li>

  413. <a href="./ems_es_ep_ex.html#ems_es_ep_ex">Example calculations for the potential</a><span class="headline-id">ems.es.ep.ex</span>

  414. 

  415. </li>

  416. <li>

  417. <a href="./ems_es_ep_PL.html#ems_es_ep_PL">Poisson's and Laplace's Equations</a><span class="headline-id">ems.es.ep.PL</span>

  418. 

  419. </li>

  420. <li>

  421. <a href="./ems_es_ep_bc.html#ems_es_ep_bc">Electrostatic Boundary Conditions</a><span class="headline-id">ems.es.ep.bc</span>

  422. 

  423. </li>

  424. 

  425. </ul>

  426. </details>

  427. </li>

  428. <li>

  429. <a href="./ems_es_e.html#ems_es_e">Electrostatic Energy from the Potential</a><span class="headline-id">ems.es.e</span>

  430. 

  431. </li>

  432. <li>

  433. 

  434. <details>

  435. <summary>

  436. <a href="./ems_es_c.html#ems_es_c">Conductors</a><span class="headline-id">ems.es.c</span>

  437. 

  438. 

  439. </summary>

  440. <ul>

  441. <li>

  442. <a href="./ems_es_c_p.html#ems_es_c_p">Properties</a><span class="headline-id">ems.es.c.p</span>

  443. 

  444. </li>

  445. <li>

  446. <a href="./ems_es_c_ic.html#ems_es_c_ic">Induced Charges</a><span class="headline-id">ems.es.c.ic</span>

  447. 

  448. </li>

  449. <li>

  450. <a href="./ems_es_c_sc.html#ems_es_c_sc">Surface Charge and the Force on a Conductor</a><span class="headline-id">ems.es.c.sc</span>

  451. 

  452. </li>

  453. <li>

  454. <a href="./ems_es_c_cap.html#ems_es_c_cap">Capacitors</a><span class="headline-id">ems.es.c.cap</span>

  455. 

  456. </li>

  457. 

  458. </ul>

  459. </details>

  460. </li>

  461. 

  462. </ul>

  463. </details>

  464. </li>

  465. <li>

  466. 

  467. <details open="">

  468. <summary class="toc-open">

  469. <a href="./ems_ca.html#ems_ca">Calculating or Approximating the Electrostatic Potential</a><span class="headline-id">ems.ca</span>

  470. 

  471. 

  472. </summary>

  473. <ul>

  474. <li>

  475. 

  476. <details>

  477. <summary>

  478. <a href="./ems_ca_fe.html#ems_ca_fe">Fundamental Equations for the Electrostatic Potential</a><span class="headline-id">ems.ca.fe</span>

  479. 

  480. 

  481. </summary>

  482. <ul>

  483. <li>

  484. <a href="./ems_ca_fe_L.html#ems_ca_fe_L">The Laplace Equation</a><span class="headline-id">ems.ca.fe.L</span>

  485. 

  486. </li>

  487. <li>

  488. <a href="./ems_ca_fe_g.html#ems_ca_fe_g">Green's Identities</a><span class="headline-id">ems.ca.fe.g</span>

  489. 

  490. </li>

  491. <li>

  492. <a href="./ems_ca_fe_uP.html#ems_ca_fe_uP">Uniqueness of Solution to Poisson's Equation</a><span class="headline-id">ems.ca.fe.uP</span>

  493. 

  494. </li>

  495. 

  496. </ul>

  497. </details>

  498. </li>

  499. <li>

  500. 

  501. <details>

  502. <summary>

  503. <a href="./ems_ca_mi.html#ems_ca_mi">The Method of Images</a><span class="headline-id">ems.ca.mi</span>

  504. 

  505. 

  506. </summary>

  507. <ul>

  508. <li>

  509. <a href="./ems_ca_mi_isc.html#ems_ca_mi_isc">Induced Surface Charges</a><span class="headline-id">ems.ca.mi.isc</span>

  510. 

  511. </li>

  512. <li>

  513. <a href="./ems_ca_mi_fe.html#ems_ca_mi_fe">Force and Energy</a><span class="headline-id">ems.ca.mi.fe</span>

  514. 

  515. </li>

  516. <li>

  517. <a href="./ems_ca_mi_o.html#ems_ca_mi_o">Other Image Problems</a><span class="headline-id">ems.ca.mi.o</span>

  518. 

  519. </li>

  520. 

  521. </ul>

  522. </details>

  523. </li>

  524. <li>

  525. 

  526. <details>

  527. <summary>

  528. <a href="./ems_ca_sv.html#ems_ca_sv">Separation of Variables</a><span class="headline-id">ems.ca.sv</span>

  529. 

  530. 

  531. </summary>

  532. <ul>

  533. <li>

  534. <a href="./ems_ca_sv_car.html#ems_ca_sv_car">Cartesian Coordinates</a><span class="headline-id">ems.ca.sv.car</span>

  535. 

  536. </li>

  537. <li>

  538. <a href="./ems_ca_sv_cyl.html#ems_ca_sv_cyl">Cylindrical Coordinates</a><span class="headline-id">ems.ca.sv.cyl</span>

  539. 

  540. </li>

  541. <li>

  542. <a href="./ems_ca_sv_sph.html#ems_ca_sv_sph">Spherical Coordinates</a><span class="headline-id">ems.ca.sv.sph</span>

  543. 

  544. </li>

  545. 

  546. </ul>

  547. </details>

  548. </li>

  549. <li>

  550. 

  551. <details open="">

  552. <summary class="toc-open">

  553. <a href="./ems_ca_me.html#ems_ca_me">The Multipole Expansion</a><span class="headline-id">ems.ca.me</span>

  554. 

  555. 

  556. </summary>

  557. <ul>

  558. <li class="toc-currentpage">

  559. <a href="./ems_ca_me_a.html#ems_ca_me_a">Approximate Potential at Large Distance</a><span class="headline-id">ems.ca.me.a</span>

  560. 

  561. </li>

  562. <li>

  563. <a href="./ems_ca_me_md.html#ems_ca_me_md">Monopole and Dipole Terms</a><span class="headline-id">ems.ca.me.md</span>

  564. 

  565. </li>

  566. <li>

  567. <a href="./ems_ca_me_h.html#ems_ca_me_h">Higher Moments</a><span class="headline-id">ems.ca.me.h</span>

  568. 

  569. </li>

  570. <li>

  571. <a href="./ems_ca_me_Ed.html#ems_ca_me_Ed">The Electric Field of a Dipole</a><span class="headline-id">ems.ca.me.Ed</span>

  572. 

  573. </li>

  574. <li>

  575. <a href="./ems_ca_me_Eq.html#ems_ca_me_Eq">The Electric Field of a Quadrupole</a><span class="headline-id">ems.ca.me.Eq</span>

  576. 

  577. </li>

  578. 

  579. </ul>

  580. </details>

  581. </li>

  582. 

  583. </ul>

  584. </details>

  585. </li>

  586. <li>

  587. 

  588. <details>

  589. <summary>

  590. <a href="./ems_ms.html#ems_ms">Magnetostatics</a><span class="headline-id">ems.ms</span>

  591. 

  592. 

  593. </summary>

  594. <ul>

  595. <li>

  596. 

  597. <details>

  598. <summary>

  599. <a href="./ems_ms_lf.html#ems_ms_lf">Charges in Motion: the Lorentz Force Law</a><span class="headline-id">ems.ms.lf</span>

  600. 

  601. 

  602. </summary>

  603. <ul>

  604. <li>

  605. <a href="./ems_ms_lf_pc.html#ems_ms_lf_pc">Point Charges</a><span class="headline-id">ems.ms.lf.pc</span>

  606. 

  607. </li>

  608. <li>

  609. <a href="./ems_ms_lf_sc.html#ems_ms_lf_sc">Steady Currents</a><span class="headline-id">ems.ms.lf.sc</span>

  610. 

  611. </li>

  612. 

  613. </ul>

  614. </details>

  615. </li>

  616. <li>

  617. <a href="./ems_ms_ce.html#ems_ms_ce">Charge Conservation and the Continuity Equation</a><span class="headline-id">ems.ms.ce</span>

  618. 

  619. </li>

  620. <li>

  621. <a href="./ems_ms_BS.html#ems_ms_BS">Steady Currents: the Biot-Savart Law</a><span class="headline-id">ems.ms.BS</span>

  622. 

  623. </li>

  624. <li>

  625. 

  626. <details>

  627. <summary>

  628. <a href="./ems_ms_dcB.html#ems_ms_dcB">Divergence and Curl of \({\bf B}\)</a><span class="headline-id">ems.ms.dcB</span>

  629. 

  630. 

  631. </summary>

  632. <ul>

  633. <li>

  634. <a href="./ems_ms_dcB_iw.html#ems_ms_dcB_iw">Simplistic case: infinite wire</a><span class="headline-id">ems.ms.dcB.iw</span>

  635. 

  636. </li>

  637. <li>

  638. <a href="./ems_ms_dcB_d.html#ems_ms_dcB_d">Divergence of \({\bf B}\) from Biot-Savart</a><span class="headline-id">ems.ms.dcB.d</span>

  639. 

  640. </li>

  641. <li>

  642. <a href="./ems_ms_dcB_c.html#ems_ms_dcB_c">Curl of \({\bf B}\) from Biot-Savart; Ampère's Law</a><span class="headline-id">ems.ms.dcB.c</span>

  643. 

  644. </li>

  645. 

  646. </ul>

  647. </details>

  648. </li>

  649. <li>

  650. 

  651. <details>

  652. <summary>

  653. <a href="./ems_ms_vp.html#ems_ms_vp">The Vector Potential</a><span class="headline-id">ems.ms.vp</span>

  654. 

  655. 

  656. </summary>

  657. <ul>

  658. <li>

  659. <a href="./ems_ms_vp_A.html#ems_ms_vp_A">Definition; Gauge Choices</a><span class="headline-id">ems.ms.vp.A</span>

  660. 

  661. </li>

  662. <li>

  663. <a href="./ems_ms_vp_mbc.html#ems_ms_vp_mbc">Magnetic Boundary Conditions</a><span class="headline-id">ems.ms.vp.mbc</span>

  664. 

  665. </li>

  666. <li>

  667. <a href="./ems_ms_vp_me.html#ems_ms_vp_me">Multipole Expansion of the Vector Potential</a><span class="headline-id">ems.ms.vp.me</span>

  668. 

  669. </li>

  670. <li>

  671. <a href="./ems_ms_vp_comp.html#ems_ms_vp_comp">Comparison of Electrostatics and Magnetostatics</a><span class="headline-id">ems.ms.vp.comp</span>

  672. 

  673. </li>

  674. <li>

  675. <a href="./ems_ms_vp_LC.html#ems_ms_vp_LC">The Levi-Civita Symbol</a><span class="headline-id">ems.ms.vp.LC</span>

  676. 

  677. </li>

  678. 

  679. </ul>

  680. </details>

  681. </li>

  682. 

  683. </ul>

  684. </details>

  685. </li>

  686. 

  687. </ul>

  688. </details>

  689. </li>

  690. <li>

  691. 

  692. <details>

  693. <summary>

  694. <a href="./emsm.html#emsm">Electromagnetostatics in matter</a><span class="headline-id">emsm</span>

  695. 

  696. 

  697. </summary>

  698. <ul>

  699. <li>

  700. 

  701. <details>

  702. <summary>

  703. <a href="./emsm_esm.html#emsm_esm">Electrostatics in matter</a><span class="headline-id">emsm.esm</span>

  704. 

  705. 

  706. </summary>

  707. <ul>

  708. <li>

  709. 

  710. <details>

  711. <summary>

  712. <a href="./emsm_esm_mE.html#emsm_esm_mE">Matter Bathed in E Fields; Polarization</a><span class="headline-id">emsm.esm.mE</span>

  713. 

  714. 

  715. </summary>

  716. <ul>

  717. <li>

  718. <a href="./emsm_esm_mE_o.html#emsm_esm_mE_o">Overview</a><span class="headline-id">emsm.esm.mE.o</span>

  719. 

  720. </li>

  721. <li>

  722. <a href="./emsm_esm_mE_P.html#emsm_esm_mE_P">Polarization</a><span class="headline-id">emsm.esm.mE.P</span>

  723. 

  724. </li>

  725. 

  726. </ul>

  727. </details>

  728. </li>

  729. <li>

  730. 

  731. <details>

  732. <summary>

  733. <a href="./emsm_esm_po.html#emsm_esm_po">Polarized Objects; Bound Charges</a><span class="headline-id">emsm.esm.po</span>

  734. 

  735. 

  736. </summary>

  737. <ul>

  738. <li>

  739. <a href="./emsm_esm_po_pibc.html#emsm_esm_po_pibc">Physical Interpretation of Bound Charges</a><span class="headline-id">emsm.esm.po.pibc</span>

  740. 

  741. </li>

  742. <li>

  743. <a href="./emsm_esm_po_fid.html#emsm_esm_po_fid">The Field Inside a Dielectric</a><span class="headline-id">emsm.esm.po.fid</span>

  744. 

  745. </li>

  746. 

  747. </ul>

  748. </details>

  749. </li>

  750. <li>

  751. 

  752. <details>

  753. <summary>

  754. <a href="./emsm_esm_D.html#emsm_esm_D">The Electric Displacement</a><span class="headline-id">emsm.esm.D</span>

  755. 

  756. 

  757. </summary>

  758. <ul>

  759. <li>

  760. <a href="./emsm_esm_D_bc.html#emsm_esm_D_bc">Boundary Conditions</a><span class="headline-id">emsm.esm.D.bc</span>

  761. 

  762. </li>

  763. 

  764. </ul>

  765. </details>

  766. </li>

  767. <li>

  768. <a href="./emsm_esm_di.html#emsm_esm_di">Dielectrics</a><span class="headline-id">emsm.esm.di</span>

  769. 

  770. </li>

  771. <li>

  772. 

  773. <details>

  774. <summary>

  775. <a href="./emsm_esm_ld.html#emsm_esm_ld">Linear Dielectrics</a><span class="headline-id">emsm.esm.ld</span>

  776. 

  777. 

  778. </summary>

  779. <ul>

  780. <li>

  781. <a href="./emsm_esm_ld_sp.html#emsm_esm_ld_sp">Susceptibility, Permittivity, Dielectric Constant</a><span class="headline-id">emsm.esm.ld.sp</span>

  782. 

  783. </li>

  784. <li>

  785. <a href="./emsm_esm_ld_bvp.html#emsm_esm_ld_bvp">Boundary Value Problems with Linear Dielectrics</a><span class="headline-id">emsm.esm.ld.bvp</span>

  786. 

  787. </li>

  788. <li>

  789. <a href="./emsm_esm_ld_e.html#emsm_esm_ld_e">Energy in Dielectric Systems</a><span class="headline-id">emsm.esm.ld.e</span>

  790. 

  791. </li>

  792. <li>

  793. <a href="./emsm_esm_ld_f.html#emsm_esm_ld_f">Forces on Dielectrics</a><span class="headline-id">emsm.esm.ld.f</span>

  794. 

  795. </li>

  796. 

  797. </ul>

  798. </details>

  799. </li>

  800. 

  801. </ul>

  802. </details>

  803. </li>

  804. <li>

  805. 

  806. <details>

  807. <summary>

  808. <a href="./emsm_msm.html#emsm_msm">Magnetostatics in matter</a><span class="headline-id">emsm.msm</span>

  809. 

  810. 

  811. </summary>

  812. <ul>

  813. <li>

  814. 

  815. <details>

  816. <summary>

  817. <a href="./emsm_msm_m.html#emsm_msm_m">Magnetization</a><span class="headline-id">emsm.msm.m</span>

  818. 

  819. 

  820. </summary>

  821. <ul>

  822. <li>

  823. <a href="./emsm_msm_m_dpf.html#emsm_msm_m_dpf">Diamagnetism, Paramagnetism, Ferromagnetism</a><span class="headline-id">emsm.msm.m.dpf</span>

  824. 

  825. </li>

  826. <li>

  827. <a href="./emsm_msm_m_fdi.html#emsm_msm_m_fdi">Torques and Forces on Magnetic Dipoles</a><span class="headline-id">emsm.msm.m.fdi</span>

  828. 

  829. </li>

  830. <li>

  831. <a href="./emsm_msm_a.html#emsm_msm_a">Effect of Magnetic Field on Atomic Orbits</a><span class="headline-id">emsm.msm.a</span>

  832. 

  833. </li>

  834. 

  835. </ul>

  836. </details>

  837. </li>

  838. <li>

  839. 

  840. <details>

  841. <summary>

  842. <a href="./emsm_msm_fmo.html#emsm_msm_fmo">The Field of a Magnetized Object</a><span class="headline-id">emsm.msm.fmo</span>

  843. 

  844. 

  845. </summary>

  846. <ul>

  847. <li>

  848. <a href="./emsm_msm_fmo_bc.html#emsm_msm_fmo_bc">Bound Currents</a><span class="headline-id">emsm.msm.fmo.bc</span>

  849. 

  850. </li>

  851. <li>

  852. <a href="./emsm_msm_fmo_pibc.html#emsm_msm_fmo_pibc">Physical Interpretation of Bound Currents</a><span class="headline-id">emsm.msm.fmo.pibc</span>

  853. 

  854. </li>

  855. <li>

  856. <a href="./emsm_msm_fmo_fim.html#emsm_msm_fmo_fim">The Magnetic Field Inside Matter</a><span class="headline-id">emsm.msm.fmo.fim</span>

  857. 

  858. </li>

  859. 

  860. </ul>

  861. </details>

  862. </li>

  863. <li>

  864. 

  865. <details>

  866. <summary>

  867. <a href="./emsm_msm_H.html#emsm_msm_H">The H Field</a><span class="headline-id">emsm.msm.H</span>

  868. 

  869. 

  870. </summary>

  871. <ul>

  872. <li>

  873. <a href="./emsm_msm_H_A.html#emsm_msm_H_A">Ampère's Law in Magnetized Materials</a><span class="headline-id">emsm.msm.H.A</span>

  874. 

  875. </li>

  876. 

  877. </ul>

  878. </details>

  879. </li>

  880. <li>

  881. 

  882. <details>

  883. <summary>

  884. <a href="./emsm_msm_lnlm.html#emsm_msm_lnlm">Linear and Nonlinear Media</a><span class="headline-id">emsm.msm.lnlm</span>

  885. 

  886. 

  887. </summary>

  888. <ul>

  889. <li>

  890. <a href="./emsm_msm_lnlm_sp.html#emsm_msm_lnlm_sp">Magnetic Susceptibility and Permeability</a><span class="headline-id">emsm.msm.lnlm.sp</span>

  891. 

  892. </li>

  893. <li>

  894. <a href="./emsm_msm_lnlm_fm.html#emsm_msm_lnlm_fm">Ferromagnetism</a><span class="headline-id">emsm.msm.lnlm.fm</span>

  895. 

  896. </li>

  897. 

  898. </ul>

  899. </details>

  900. </li>

  901. 

  902. </ul>

  903. </details>

  904. </li>

  905. 

  906. </ul>

  907. </details>

  908. </li>

  909. <li>

  910. 

  911. <details>

  912. <summary>

  913. <a href="./emd.html#emd">Electromagnetodynamics</a><span class="headline-id">emd</span>

  914. 

  915. 

  916. </summary>

  917. <ul>

  918. <li>

  919. 

  920. <details>

  921. <summary>

  922. <a href="./emd_Fl.html#emd_Fl">Induction: Faraday's Law</a><span class="headline-id">emd.Fl</span>

  923. 

  924. 

  925. </summary>

  926. <ul>

  927. <li>

  928. <a href="./emd_Fl_Fl.html#emd_Fl_Fl">Faraday's Law</a><span class="headline-id">emd.Fl.Fl</span>

  929. 

  930. </li>

  931. <li>

  932. <a href="./emd_Fl_ief.html#emd_Fl_ief">The Induced Electric Field</a><span class="headline-id">emd.Fl.ief</span>

  933. 

  934. </li>

  935. <li>

  936. <a href="./emd_Fl_i.html#emd_Fl_i">Inductance</a><span class="headline-id">emd.Fl.i</span>

  937. 

  938. </li>

  939. <li>

  940. <a href="./emd_Fl_e.html#emd_Fl_e">Energy in Magnetic Fields</a><span class="headline-id">emd.Fl.e</span>

  941. 

  942. </li>

  943. 

  944. </ul>

  945. </details>

  946. </li>

  947. <li>

  948. 

  949. <details>

  950. <summary>

  951. <a href="./emd_Me.html#emd_Me">Maxwell's Equations</a><span class="headline-id">emd.Me</span>

  952. 

  953. 

  954. </summary>

  955. <ul>

  956. <li>

  957. <a href="./emd_Me_ebM.html#emd_Me_ebM">Electrodynamics Before Maxwell</a><span class="headline-id">emd.Me.ebM</span>

  958. 

  959. </li>

  960. <li>

  961. <a href="./emd_Me_dc.html#emd_Me_dc">Maxwell's Correction to Ampère's Law; the Displacement Current</a><span class="headline-id">emd.Me.dc</span>

  962. 

  963. </li>

  964. <li>

  965. <a href="./emd_Me_Me.html#emd_Me_Me">Maxwell's Equations</a><span class="headline-id">emd.Me.Me</span>

  966. 

  967. </li>

  968. <li>

  969. <a href="./emd_Me_mc.html#emd_Me_mc">Magnetic Charge</a><span class="headline-id">emd.Me.mc</span>

  970. 

  971. </li>

  972. 

  973. </ul>

  974. </details>

  975. </li>

  976. <li>

  977. 

  978. <details>

  979. <summary>

  980. <a href="./emd_ce.html#emd_ce">Charge and Energy Flows</a><span class="headline-id">emd.ce</span>

  981. 

  982. 

  983. </summary>

  984. <ul>

  985. <li>

  986. <a href="./emd_ce_ce.html#emd_ce_ce">The Continuity Equation</a><span class="headline-id">emd.ce.ce</span>

  987. 

  988. </li>

  989. <li>

  990. <a href="./emd_ce_poy.html#emd_ce_poy">Poynting's Theorem; the Poynting Vector</a><span class="headline-id">emd.ce.poy</span>

  991. 

  992. </li>

  993. <li>

  994. <a href="./emd_ce_mst.html#emd_ce_mst">Maxwell's Stress Tensor</a><span class="headline-id">emd.ce.mst</span>

  995. 

  996. </li>

  997. <li>

  998. <a href="./emd_ce_mom.html#emd_ce_mom">Momentum</a><span class="headline-id">emd.ce.mom</span>

  999. 

  1000. </li>

  1001. <li>

  1002. <a href="./emd_ce_amom.html#emd_ce_amom">Angular Momentum</a><span class="headline-id">emd.ce.amom</span>

  1003. 

  1004. </li>

  1005. 

  1006. </ul>

  1007. </details>

  1008. </li>

  1009. <li>

  1010. 

  1011. <details>

  1012. <summary>

  1013. <a href="./emd_emw.html#emd_emw">Electromagnetic waves in vacuum</a><span class="headline-id">emd.emw</span>

  1014. 

  1015. 

  1016. </summary>

  1017. <ul>

  1018. <li>

  1019. <a href="./emd_emw_we.html#emd_emw_we">The Wave Equation</a><span class="headline-id">emd.emw.we</span>

  1020. 

  1021. </li>

  1022. <li>

  1023. <a href="./emd_emw_mpw.html#emd_emw_mpw">Monochromatic Plane Waves</a><span class="headline-id">emd.emw.mpw</span>

  1024. 

  1025. </li>

  1026. <li>

  1027. <a href="./emd_emw_ep.html#emd_emw_ep">Energy and Momentum</a><span class="headline-id">emd.emw.ep</span>

  1028. 

  1029. </li>

  1030. 

  1031. </ul>

  1032. </details>

  1033. </li>

  1034. 

  1035. </ul>

  1036. </details>

  1037. </li>

  1038. <li>

  1039. 

  1040. <details>

  1041. <summary>

  1042. <a href="./emdm.html#emdm">Electromagnetodynamics in Matter</a><span class="headline-id">emdm</span>

  1043. 

  1044. 

  1045. </summary>

  1046. <ul>

  1047. <li>

  1048. 

  1049. <details>

  1050. <summary>

  1051. <a href="./emdm_Me.html#emdm_Me">Maxwell's Equations in Matter</a><span class="headline-id">emdm.Me</span>

  1052. 

  1053. 

  1054. </summary>

  1055. <ul>

  1056. <li>

  1057. <a href="./emdm_Me_Mem.html#emdm_Me_Mem">Maxwell's Equations in Matter</a><span class="headline-id">emdm.Me.Mem</span>

  1058. 

  1059. </li>

  1060. <li>

  1061. <a href="./emdm_Me_bc.html#emdm_Me_bc">Boundary Conditions</a><span class="headline-id">emdm.Me.bc</span>

  1062. 

  1063. </li>

  1064. 

  1065. </ul>

  1066. </details>

  1067. </li>

  1068. <li>

  1069. 

  1070. <details>

  1071. <summary>

  1072. <a href="./emdm_emwm.html#emdm_emwm">Electromagnetic Waves in Matter</a><span class="headline-id">emdm.emwm</span>

  1073. 

  1074. 

  1075. </summary>

  1076. <ul>

  1077. <li>

  1078. <a href="./emdm_emwm_plm.html#emdm_emwm_plm">Propagation in Linear Media</a><span class="headline-id">emdm.emwm.plm</span>

  1079. 

  1080. </li>

  1081. <li>

  1082. <a href="./emdm_emwm_refr.html#emdm_emwm_refr">Refraction</a><span class="headline-id">emdm.emwm.refr</span>

  1083. 

  1084. </li>

  1085. <li>

  1086. 

  1087. <details>

  1088. <summary>

  1089. <a href="./emdm_emwm_refl.html#emdm_emwm_refl">Reflection and Transmission</a><span class="headline-id">emdm.emwm.refl</span>

  1090. 

  1091. 

  1092. </summary>

  1093. <ul>

  1094. <li>

  1095. <a href="./emdm_emwm_refl_ni.html#emdm_emwm_refl_ni">Normal Incidence</a><span class="headline-id">emdm.emwm.refl.ni</span>

  1096. 

  1097. </li>

  1098. <li>

  1099. <a href="./emdm_emwm_refl_oi.html#emdm_emwm_refl_oi">Oblique Incidence</a><span class="headline-id">emdm.emwm.refl.oi</span>

  1100. 

  1101. </li>

  1102. 

  1103. </ul>

  1104. </details>

  1105. </li>

  1106. <li>

  1107. 

  1108. <details>

  1109. <summary>

  1110. <a href="./emdm_emwm_ad.html#emdm_emwm_ad">Absorption and Dispersion</a><span class="headline-id">emdm.emwm.ad</span>

  1111. 

  1112. 

  1113. </summary>

  1114. <ul>

  1115. <li>

  1116. <a href="./emdm_emwm_ad_c.html#emdm_emwm_ad_c">EM Waves in Conductors</a><span class="headline-id">emdm.emwm.ad.c</span>

  1117. 

  1118. </li>

  1119. 

  1120. </ul>

  1121. </details>

  1122. </li>

  1123. <li>

  1124. 

  1125. <details>

  1126. <summary>

  1127. <a href="./emdm_emwm_wg.html#emdm_emwm_wg">Waveguides</a><span class="headline-id">emdm.emwm.wg</span>

  1128. 

  1129. 

  1130. </summary>

  1131. <ul>

  1132. <li>

  1133. <a href="./emdm_emwm_wg_gw.html#emdm_emwm_wg_gw">Guided waves</a><span class="headline-id">emdm.emwm.wg.gw</span>

  1134. 

  1135. </li>

  1136. <li>

  1137. <a href="./emdm_emwm_wg_r.html#emdm_emwm_wg_r">Rectangular Waveguides</a><span class="headline-id">emdm.emwm.wg.r</span>

  1138. 

  1139. </li>

  1140. <li>

  1141. <a href="./emdm_emwm_wg_c.html#emdm_emwm_wg_c">Coaxial Lines</a><span class="headline-id">emdm.emwm.wg.c</span>

  1142. 

  1143. </li>

  1144. 

  1145. </ul>

  1146. </details>

  1147. </li>

  1148. 

  1149. </ul>

  1150. </details>

  1151. </li>

  1152. 

  1153. </ul>

  1154. </details>

  1155. </li>

  1156. <li>

  1157. 

  1158. <details>

  1159. <summary>

  1160. <a href="./emf.html#emf">Electromagnetic Fields</a><span class="headline-id">emf</span>

  1161. 

  1162. 

  1163. </summary>

  1164. <ul>

  1165. <li>

  1166. <a href="./emf_svp.html#emf_svp">Scalar and Vector Potentials</a><span class="headline-id">emf.svp</span>

  1167. 

  1168. </li>

  1169. <li>

  1170. 

  1171. <details>

  1172. <summary>

  1173. <a href="./emf_g.html#emf_g">Gauge Freedom and Choices</a><span class="headline-id">emf.g</span>

  1174. 

  1175. 

  1176. </summary>

  1177. <ul>

  1178. <li>

  1179. <a href="./emf_g_Cg.html#emf_g_Cg">Coulomb Gauge</a><span class="headline-id">emf.g.Cg</span>

  1180. 

  1181. </li>

  1182. <li>

  1183. <a href="./emf_g_Lg.html#emf_g_Lg">Lorenz Gauge; d'Alembertian; Inhomogeneous Maxwell Equations</a><span class="headline-id">emf.g.Lg</span>

  1184. 

  1185. </li>

  1186. 

  1187. </ul>

  1188. </details>

  1189. </li>

  1190. 

  1191. </ul>

  1192. </details>

  1193. </li>

  1194. <li>

  1195. 

  1196. <details>

  1197. <summary>

  1198. <a href="./red.html#red">Relativistic Electrodynamics</a><span class="headline-id">red</span>

  1199. 

  1200. 

  1201. </summary>

  1202. <ul>

  1203. <li>

  1204. 

  1205. <details>

  1206. <summary>

  1207. <a href="./red_sr.html#red_sr">Special Relativity</a><span class="headline-id">red.sr</span>

  1208. 

  1209. 

  1210. </summary>

  1211. <ul>

  1212. <li>

  1213. <a href="./red_sr_p.html#red_sr_p">Postulates and their consequences</a><span class="headline-id">red.sr.p</span>

  1214. 

  1215. </li>

  1216. <li>

  1217. <a href="./red_sr_Lt.html#red_sr_Lt">Lorentz Transformations</a><span class="headline-id">red.sr.Lt</span>

  1218. 

  1219. </li>

  1220. <li>

  1221. <a href="./red_sr_4v.html#red_sr_4v">Covariant and Contravariant Four-Vectors</a><span class="headline-id">red.sr.4v</span>

  1222. 

  1223. </li>

  1224. 

  1225. </ul>

  1226. </details>

  1227. </li>

  1228. <li>

  1229. 

  1230. <details>

  1231. <summary>

  1232. <a href="./red_rm.html#red_rm">Relativistic Mechanics</a><span class="headline-id">red.rm</span>

  1233. 

  1234. 

  1235. </summary>

  1236. <ul>

  1237. <li>

  1238. <a href="./red_rm_pt.html#red_rm_pt">Proper Time and Proper Velocity</a><span class="headline-id">red.rm.pt</span>

  1239. 

  1240. </li>

  1241. <li>

  1242. <a href="./red_rm_rme.html#red_rm_rme">Relativistic Momentum and Energy</a><span class="headline-id">red.rm.rme</span>

  1243. 

  1244. </li>

  1245. <li>

  1246. <a href="./red_rm_Mf.html#red_rm_Mf">Relativistic version of Newton's Laws; the Minkowski Force</a><span class="headline-id">red.rm.Mf</span>

  1247. 

  1248. </li>

  1249. 

  1250. </ul>

  1251. </details>

  1252. </li>

  1253. <li>

  1254. 

  1255. <details>

  1256. <summary>

  1257. <a href="./red_rem.html#red_rem">Relativistic Electromagnetism</a><span class="headline-id">red.rem</span>

  1258. 

  1259. 

  1260. </summary>

  1261. <ul>

  1262. <li>

  1263. <a href="./red_rem_mre.html#red_rem_mre">Magnetism as a Relativistic Effect</a><span class="headline-id">red.rem.mre</span>

  1264. 

  1265. </li>

  1266. <li>

  1267. <a href="./red_rem_Ltf.html#red_rem_Ltf">Lorentz Transformation of Electromagnetic Fields</a><span class="headline-id">red.rem.Ltf</span>

  1268. 

  1269. </li>

  1270. <li>

  1271. <a href="./red_rem_Fmunu.html#red_rem_Fmunu">The Field Tensor</a><span class="headline-id">red.rem.Fmunu</span>

  1272. 

  1273. </li>

  1274. <li>

  1275. <a href="./red_rem_Me.html#red_rem_Me">Maxwell's Equations in Relativistic Notation</a><span class="headline-id">red.rem.Me</span>

  1276. 

  1277. </li>

  1278. 

  1279. </ul>

  1280. </details>

  1281. </li>

  1282. 

  1283. </ul>

  1284. </details>

  1285. </li>

  1286. <li>

  1287. 

  1288. <details>

  1289. <summary>

  1290. <a href="./qed.html#qed">Quantum Electrodynamics</a><span class="headline-id">qed</span>

  1291. 

  1292. 

  1293. </summary>

  1294. <ul>

  1295. <li>

  1296. <a href="./qed_L.html#qed_L">Lagrangian</a><span class="headline-id">qed.L</span>

  1297. 

  1298. </li>

  1299. 

  1300. </ul>

  1301. </details>

  1302. </li>

  1303. <li>

  1304. 

  1305. <details>

  1306. <summary>

  1307. <a href="./d.html#d">Diagnostics</a><span class="headline-id">d</span>

  1308. 

  1309. 

  1310. </summary>

  1311. <ul>

  1312. <li>

  1313. <a href="./d_ems.html#d_ems">Diagnostics: Electromagnetostatics</a><span class="headline-id">d.ems</span>

  1314. 

  1315. </li>

  1316. <li>

  1317. <a href="./d_ems_ca.html#d_ems_ca">Diagnostics: Calculating or Approximating the Electostatic Potential</a><span class="headline-id">d.ems.ca</span>

  1318. 

  1319. </li>

  1320. <li>

  1321. <a href="./d_emsm.html#d_emsm">Diagnostics: Electromagnetostatics in Matter</a><span class="headline-id">d.emsm</span>

  1322. 

  1323. </li>

  1324. <li>

  1325. <a href="./d_ems_ms.html#d_ems_ms">Diagnostics: Magnetostatics</a><span class="headline-id">d.ems.ms</span>

  1326. 

  1327. </li>

  1328. <li>

  1329. <a href="./d_emsm_msm.html#d_emsm_msm">Diagnostics: Magnetostatics in Matter</a><span class="headline-id">d.emsm.msm</span>

  1330. 

  1331. </li>

  1332. <li>

  1333. <a href="./d_emd.html#d_emd">Diagnostics: Electromagnetodynamics</a><span class="headline-id">d.emd</span>

  1334. 

  1335. </li>

  1336. <li>

  1337. <a href="./d_emd_ce.html#d_emd_ce">Diagnostics: Conservation Laws</a><span class="headline-id">d.emd.ce</span>

  1338. 

  1339. </li>

  1340. <li>

  1341. <a href="./d_emd_emw.html#d_emd_emw">Diagnostics: Electromagnetic Waves</a><span class="headline-id">d.emd.emw</span>

  1342. 

  1343. </li>

  1344. <li>

  1345. <a href="./d_emf.html#d_emf">Diagnostics: Potentials, Gauges and Fields</a><span class="headline-id">d.emf</span>

  1346. 

  1347. </li>

  1348. <li>

  1349. <a href="./d_red.html#d_red">Diagnostics: Relativistic Electrodynamics</a><span class="headline-id">d.red</span>

  1350. 

  1351. </li>

  1352. <li>

  1353. <a href="./d_m.html#d_m">Diagnostics: Compendium - Mathematics</a><span class="headline-id">d.m</span>

  1354. 

  1355. </li>

  1356. 

  1357. </ul>

  1358. </details>

  1359. </li>

  1360. <li>

  1361. 

  1362. <details>

  1363. <summary>

  1364. <a href="./a.html#a">Appendices</a><span class="headline-id">a</span>

  1365. 

  1366. 

  1367. </summary>

  1368. <ul>

  1369. <li>

  1370. <a href="./a_l.html#a_l">Literature</a><span class="headline-id">a.l</span>

  1371. 

  1372. </li>

  1373. 

  1374. </ul>

  1375. </details>

  1376. </li>

  1377. <li>

  1378. 

  1379. <details>

  1380. <summary>

  1381. <a href="./c.html#c">Compendium</a><span class="headline-id">c</span>

  1382. 

  1383. 

  1384. </summary>

  1385. <ul>

  1386. <li>

  1387. 

  1388. <details>

  1389. <summary>

  1390. <a href="./c_m.html#c_m">Mathematics</a><span class="headline-id">c.m</span>

  1391. 

  1392. 

  1393. </summary>

  1394. <ul>

  1395. <li>

  1396. 

  1397. <details>

  1398. <summary>

  1399. <a href="./c_m_va.html#c_m_va">Vector Analysis</a><span class="headline-id">c.m.va</span>

  1400. 

  1401. 

  1402. </summary>

  1403. <ul>

  1404. <li>

  1405. <a href="./c_m_va_n.html#c_m_va_n">Notation and algebraic properties</a><span class="headline-id">c.m.va.n</span>

  1406. 

  1407. </li>

  1408. <li>

  1409. <a href="./c_m_va_sp.html#c_m_va_sp">Scalar product</a><span class="headline-id">c.m.va.sp</span>

  1410. 

  1411. </li>

  1412. <li>

  1413. <a href="./c_m_va_cp.html#c_m_va_cp">Cross product</a><span class="headline-id">c.m.va.cp</span>

  1414. 

  1415. </li>

  1416. <li>

  1417. <a href="./c_m_va_tp.html#c_m_va_tp">Triple Products</a><span class="headline-id">c.m.va.tp</span>

  1418. 

  1419. </li>

  1420. <li>

  1421. <a href="./c_m_va_pds.html#c_m_va_pds">Position, Displacement and Separation Vectors</a><span class="headline-id">c.m.va.pds</span>

  1422. 

  1423. </li>

  1424. 

  1425. </ul>

  1426. </details>

  1427. </li>

  1428. <li>

  1429. 

  1430. <details>

  1431. <summary>

  1432. <a href="./c_m_dc.html#c_m_dc">Differential Calculus</a><span class="headline-id">c.m.dc</span>

  1433. 

  1434. 

  1435. </summary>

  1436. <ul>

  1437. <li>

  1438. <a href="./c_m_dc_g.html#c_m_dc_g">Gradient</a><span class="headline-id">c.m.dc.g</span>

  1439. 

  1440. </li>

  1441. <li>

  1442. <a href="./c_m_dc_del.html#c_m_dc_del">The \({\boldsymbol \nabla}\) Operator</a><span class="headline-id">c.m.dc.del</span>

  1443. 

  1444. </li>

  1445. <li>

  1446. <a href="./c_m_dc_div.html#c_m_dc_div">The Divergence</a><span class="headline-id">c.m.dc.div</span>

  1447. 

  1448. </li>

  1449. <li>

  1450. <a href="./c_m_dc_curl.html#c_m_dc_curl">The Curl</a><span class="headline-id">c.m.dc.curl</span>

  1451. 

  1452. </li>

  1453. <li>

  1454. <a href="./c_m_dc_pr.html#c_m_dc_pr">Product arguments</a><span class="headline-id">c.m.dc.pr</span>

  1455. 

  1456. </li>

  1457. <li>

  1458. <a href="./c_m_dc_d2.html#c_m_dc_d2">Second Derivatives</a><span class="headline-id">c.m.dc.d2</span>

  1459. 

  1460. </li>

  1461. 

  1462. </ul>

  1463. </details>

  1464. </li>

  1465. <li>

  1466. 

  1467. <details>

  1468. <summary>

  1469. <a href="./c_m_ic.html#c_m_ic">Integral Calculus</a><span class="headline-id">c.m.ic</span>

  1470. 

  1471. 

  1472. </summary>

  1473. <ul>

  1474. <li>

  1475. <a href="./c_m_ic_lsv.html#c_m_ic_lsv">Line, Surface and Volume Integrals</a><span class="headline-id">c.m.ic.lsv</span>

  1476. 

  1477. </li>

  1478. <li>

  1479. <a href="./c_m_ic_ftc.html#c_m_ic_ftc">The Fundamental Theorem of Calculus</a><span class="headline-id">c.m.ic.ftc</span>

  1480. 

  1481. </li>

  1482. <li>

  1483. <a href="./c_m_ic_ftg.html#c_m_ic_ftg">The Fundamental Theorem for Gradients</a><span class="headline-id">c.m.ic.ftg</span>

  1484. 

  1485. </li>

  1486. <li>

  1487. <a href="./c_m_ic_gauss.html#c_m_ic_gauss">Gauss' Theorem</a><span class="headline-id">c.m.ic.gauss</span>

  1488. 

  1489. </li>

  1490. <li>

  1491. <a href="./c_m_ic_stokes.html#c_m_ic_stokes">Stokes' Theorem</a><span class="headline-id">c.m.ic.stokes</span>

  1492. 

  1493. </li>

  1494. <li>

  1495. <a href="./c_m_ic_ip.html#c_m_ic_ip">Integration by Parts</a><span class="headline-id">c.m.ic.ip</span>

  1496. 

  1497. </li>

  1498. 

  1499. </ul>

  1500. </details>

  1501. </li>

  1502. <li>

  1503. 

  1504. <details>

  1505. <summary>

  1506. <a href="./c_m_cs.html#c_m_cs">Coordinate Systems</a><span class="headline-id">c.m.cs</span>

  1507. 

  1508. 

  1509. </summary>

  1510. <ul>

  1511. <li>

  1512. <a href="./c_m_cs_sph.html#c_m_cs_sph">Spherical Coordinates</a><span class="headline-id">c.m.cs.sph</span>

  1513. 

  1514. </li>

  1515. <li>

  1516. <a href="./c_m_cs_cyl.html#c_m_cs_cyl">Cylindrical Coordinates</a><span class="headline-id">c.m.cs.cyl</span>

  1517. 

  1518. </li>

  1519. <li>

  1520. <a href="./c_m_cs_hyp.html#c_m_cs_hyp">Hyperbolic Coordinates</a><span class="headline-id">c.m.cs.hyp</span>

  1521. 

  1522. </li>

  1523. 

  1524. </ul>

  1525. </details>

  1526. </li>

  1527. <li>

  1528. 

  1529. <details>

  1530. <summary>

  1531. <a href="./c_m_dd.html#c_m_dd">Dirac delta Distribution</a><span class="headline-id">c.m.dd</span>

  1532. 

  1533. 

  1534. </summary>

  1535. <ul>

  1536. <li>

  1537. <a href="./c_m_dd_div.html#c_m_dd_div">The Divergence of \(\hat{\bf r}/r^2\)</a><span class="headline-id">c.m.dd.div</span>

  1538. 

  1539. </li>

  1540. <li>

  1541. <a href="./c_m_dd_1d.html#c_m_dd_1d">The One-Dimensional Dirac Delta Function</a><span class="headline-id">c.m.dd.1d</span>

  1542. 

  1543. </li>

  1544. <li>

  1545. <a href="./c_m_dd_3d.html#c_m_dd_3d">The Three-Dimensional Delta Function</a><span class="headline-id">c.m.dd.3d</span>

  1546. 

  1547. </li>

  1548. 

  1549. </ul>

  1550. </details>

  1551. </li>

  1552. <li>

  1553. 

  1554. <details>

  1555. <summary>

  1556. <a href="./c_m_vf.html#c_m_vf">Vector Fields</a><span class="headline-id">c.m.vf</span>

  1557. 

  1558. 

  1559. </summary>

  1560. <ul>

  1561. <li>

  1562. <a href="./c_m_vf_helm.html#c_m_vf_helm">The Helmholtz Theorem</a><span class="headline-id">c.m.vf.helm</span>

  1563. 

  1564. </li>

  1565. <li>

  1566. <a href="./c_m_vf_pot.html#c_m_vf_pot">Potentials</a><span class="headline-id">c.m.vf.pot</span>

  1567. 

  1568. </li>

  1569. 

  1570. </ul>

  1571. </details>

  1572. </li>

  1573. <li>

  1574. 

  1575. <details>

  1576. <summary>

  1577. <a href="./c_m_uf.html#c_m_uf">Useful Formulas</a><span class="headline-id">c.m.uf</span>

  1578. 

  1579. 

  1580. </summary>

  1581. <ul>

  1582. <li>

  1583. <a href="./c_m_uf_cyl.html#c_m_uf_cyl">Cylindrical coordinates</a><span class="headline-id">c.m.uf.cyl</span>

  1584. 

  1585. </li>

  1586. <li>

  1587. <a href="./c_m_uf_sph.html#c_m_uf_sph">Spherical coordinates</a><span class="headline-id">c.m.uf.sph</span>

  1588. 

  1589. </li>

  1590. <li>

  1591. <a href="./c_m_uf_vi.html#c_m_uf_vi">Vector identities</a><span class="headline-id">c.m.uf.vi</span>

  1592. 

  1593. </li>

  1594. 

  1595. </ul>

  1596. </details>

  1597. </li>

  1598. 

  1599. </ul>

  1600. </details>

  1601. </li>

  1602. 

  1603. </ul>

  1604. </details>

  1605. </li>

  1606. 

  1607. </ul>

  1608. </details>

  1609. </nav>

  1610. <ul class="breadcrumbs"><li><a class="breadcrumb-link"href="ems.html">Electromagnetostatics</a></li><li><a class="breadcrumb-link"href="ems_ca.html">Calculating or Approximating the Electrostatic Potential</a></li><li><a class="breadcrumb-link"href="ems_ca_me.html">The Multipole Expansion</a></li><li>Approximate Potential at Large Distance</li></ul><ul class="navigation-links"><li>Prev:&nbsp;<a href="ems_ca_me.html">The Multipole Expansion&emsp;<small>[ems.ca.me]</small></a></li><li>Next:&nbsp;<a href="ems_ca_me_md.html">Monopole and Dipole Terms&emsp;<small>[ems.ca.me.md]</small></a></li><li>Up:&nbsp;<a href="ems_ca_me.html">The Multipole Expansion&emsp;<small>[ems.ca.me]</small></a></li></ul><div id="outline-container-ems_ca_me_a" class="outline-5">

  1611. <h5 id="ems_ca_me_a">Approximate Potential at Large Distance<a class="headline-permalink" href="./ems_ca_me_a.html#ems_ca_me_a"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">

  1612.   <path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>

  1613.   <path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>

  1614. </svg></a><span class="headline-id">ems.ca.me.a</span></h5>

  1615. <div class="outline-text-5" id="text-ems_ca_me_a">

  1616. <p>

  1617. Let's consider the spatial function in the potential for a single point source charge:

  1618. \[

  1619. \frac{1}{|{\bf r} - {\bf r}_s|}

  1620. \]

  1621. How does this look when we're at large distances \(|{\bf r}| \gg |{\bf r}_s|\)?

  1622. We can formally expand this in powers of \(|{\bf r}_s|/|{\bf r}|\). For simplicity, let's start by

  1623. putting \({\bf r} = r ~\hat{\bf z}, r &gt; 0\) and \({\bf r}_s = r_s \hat{\bf z}\), with \(|r_s| &lt; r\).

  1624. By Taylor expanding, we get

  1625. \[

  1626. \frac{1}{|{\bf r} - {\bf r}_s|} = \frac{1}{r - r_s} = \frac{1}{r} \sum_{l=0}^{\infty} \left(\frac{r_s}{r}\right)^l

  1627. \]

  1628. Formally, we could do this for any vector \({\bf r}_s\) such that \(|{\bf r}_s| &lt; |{\bf r}|\) by

  1629. Taylor expanding with the \({\boldsymbol \nabla}\) operator,

  1630. </p>

  1631. <div class="eqlabel" id="orgb48be32">

  1632. <p>

  1633. <a id="1or_grad"></a><a href="./ems_ca_me_a.html#1or_grad"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">

  1634.   <path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>

  1635.   <path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>

  1636. </svg></a>

  1637. </p>

  1638. <div class="alteqlabels" id="orge7c3a2e">

  1639. 

  1640. </div>

  1641. 

  1642. </div>

  1643. <p>

  1644. \[

  1645. \frac{1}{|{\bf r} - {\bf r}_s|} = \sum_{l=0}^{\infty} \frac{1}{l!} \left( - {\bf r}_s \cdot {\boldsymbol \nabla} \right)^l \frac{1}{r}

  1646. = \frac{1}{r} - {\bf r}_s \cdot {\boldsymbol \nabla} \frac{1}{r} + \frac{1}{2} \left({\bf r}_s \cdot {\boldsymbol \nabla} \right)^2 \frac{1}{r} + ...

  1647. \tag{1or_grad}\label{1or_grad}

  1648. \]

  1649. However, it is more practical to exploit the fact that in the configuration above,

  1650. the problem has azimuthal symmetry (since everything is on the \(\hat{\bf z}\) axis),

  1651. and therefore

  1652. the potential takes the form of the general solution of Laplace's equation <a href="./ems_ca_sv_sph.html#Lap_sph_az_sol">Lap_sph_az_sol</a>  with \(\theta = 0\).

  1653. Reading the parameters, we get \(A_l = 0\), \(B_l = r_s^l\).  Putting back a generic angle

  1654. (the coefficients remain the same), we thus get

  1655. </p>

  1656. <div class="eqlabel" id="orgf3ead78">

  1657. <p>

  1658. <a id="1or_Leg"></a><a href="./ems_ca_me_a.html#1or_Leg"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">

  1659.   <path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>

  1660.   <path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>

  1661. </svg></a>

  1662. </p>

  1663. <div class="alteqlabels" id="orga8fca88">

  1664. <ul class="org-ul">

  1665. <li>Gr(3.94)</li>

  1666. </ul>

  1667. 

  1668. </div>

  1669. 

  1670. </div>

  1671. 

  1672. \begin{equation}

  1673. \frac{1}{|{\bf r} - {\bf r}_s|} = \sum_{l=0}^{\infty} \frac{r_s^l}{r^{l+1}} P_l (\cos \theta),

  1674. \hspace{1cm} \cos \theta \equiv \hat{\bf r} \cdot \hat{\bf r}_s, \hspace{1cm} r_s &lt; r.

  1675. \tag{1or_Leg}\label{1or_Leg}

  1676. \end{equation}

  1677. 

  1678. <p>

  1679. We thus see that our beloved Legendre polynomials are quite handy beasts indeed.

  1680. Considering an arbitrary charge distribution over a volume \({\cal V}\),

  1681. we can expand the potential at a point \({\bf r}\) outside \({\cal V}\) according to

  1682. (here, we put the origin of our coordinate system closer to all points in \({\cal V}\) than to \({\bf r}\)

  1683. to ensure convergence)

  1684. </p>

  1685. <div class="eqlabel" id="orgbced9c3">

  1686. <p>

  1687. <a id="p_Leg"></a><a href="./ems_ca_me_a.html#p_Leg"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">

  1688.   <path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>

  1689.   <path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>

  1690. </svg></a>

  1691. </p>

  1692. <div class="alteqlabels" id="org24bf079">

  1693. <ul class="org-ul">

  1694. <li>Gr (3.95)</li>

  1695. </ul>

  1696. 

  1697. </div>

  1698. 

  1699. </div>

  1700. <p>

  1701. \[

  1702. \phi({\bf r}) = \frac{1}{4\pi \varepsilon_0} \sum_{l=0}^{\infty} \frac{1}{|{\bf r}|^{l+1}}

  1703. \int_{\cal V} d\tau_s |{\bf r}_s|^l P_l (\hat{\bf r} \cdot \hat{\bf r}_s) ~\rho({\bf r}_s),

  1704. \hspace{1cm} |{\bf r}| &gt; |{\bf r}_s| ~\forall~ {\bf r}_s \in {\cal V}.

  1705. \tag{p_Leg}\label{p_Leg}

  1706. \]

  1707. Keeping all the terms up to infinite order, this is an exact expansion of our potential.

  1708. The real power of this however

  1709. comes from the fact that truncating the series to only its first (few) terms

  1710. gives a very good approximation to the

  1711. original potential, as long as we are sufficiently far away from the source charges.

  1712. </p>

  1713. 

  1714. 

  1715. <p>

  1716. As a first very basic example, let us revisit the configuration we

  1717. had in equation <a href="./ems_ca_mi.html#p_di_z">p_di_z</a> which represented a (physical) electric dipole, namely

  1718. two equal and opposite charges \(\pm q\) separated by a distance \(d\).

  1719. </p>

  1720. 

  1721. <p>

  1722. To be more general, we here put \(q\) at position \({\bf d}/2\) and \(-q\) at \(-{\bf d}/2\).

  1723. The potential is then

  1724. </p>

  1725. 

  1726. <p>

  1727. \[

  1728. \phi({\bf r}) = \frac{q}{4\pi \varepsilon_0} \left( \frac{1}{|{\bf r} - {\bf d}/2|} - \frac{1}{|{\bf r} + {\bf d}/2|} \right).

  1729. \]

  1730. </p>

  1731. 

  1732. <p>

  1733. We can write

  1734. </p>

  1735. 

  1736. \begin{equation*}

  1737. |{\bf r} \pm {\bf d}/2|^2 = r^2 \pm {\bf r} \cdot {\bf d} + (d/2)^2 = r^2 \left( 1 \pm \frac{{\bf d} \cdot \hat{\bf r}}{r} + \frac{d^2}{4r^2}\right)

  1738. \end{equation*}

  1739. 

  1740. <p>

  1741. For \(r \gg d\), we can expand (immediately dropping terms of order \(d^2/r^2\))

  1742. </p>

  1743. 

  1744. <p>

  1745. \[

  1746. \frac{1}{|{\bf r} \pm {\bf d}/2|} \simeq \frac{1}{r} \left( 1 \pm \frac{{\bf d} \cdot \hat{\bf r}}{r} \right)^{-1/2}

  1747. \simeq \frac{1}{r} \left( 1 \mp \frac{{\bf d} \cdot \hat{\bf r}}{2r} \right).

  1748. \]

  1749. </p>

  1750. 

  1751. <p>

  1752. Putting things together, the leading term in the expansion <a href="./ems_ca_me_a.html#p_Leg">p_Leg</a> for the

  1753. potential of the physical dipole is given by

  1754. </p>

  1755. <div class="eqlabel" id="orgfe4f1c4">

  1756. <p>

  1757. <a id="p_physdi"></a><a href="./ems_ca_me_a.html#p_physdi"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">

  1758.   <path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>

  1759.   <path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>

  1760. </svg></a>

  1761. </p>

  1762. <div class="alteqlabels" id="orgf15f43d">

  1763. <ul class="org-ul">

  1764. <li>Gr (3.90)</li>

  1765. </ul>

  1766. 

  1767. </div>

  1768. 

  1769. </div>

  1770. <p>

  1771. \[

  1772. \phi({\bf r}) \simeq \frac{1}{4\pi \varepsilon_0} \frac{q~ {\bf d} \cdot \hat{\bf r}}{r^2}

  1773. \tag{p_physdi}\label{p_physdi}

  1774. \]

  1775. </p>

  1776. 

  1777. <p>

  1778. Thus, although the dipole is electrically neutral overall, its influence does

  1779. not vanish. Compared to a point charge, it displays two important differences:

  1780. i) it falls off with one more (inverse) power of distance, and ii) it carries

  1781. a vector direction, so its influence is not isotropic.

  1782. </p>

  1783. 

  1784. <p>

  1785. In the next section, we will revisit such dipoles, but now coming from more

  1786. generic charge configurations.

  1787. </p>

  1788. </div>

  1789. </div>

  1790. 

  1791. 

  1792. 

  1793. 

  1794. <br><ul class="navigation-links"><li>Prev:&nbsp;<a href="ems_ca_me.html">The Multipole Expansion&emsp;<small>[ems.ca.me]</small></a></li><li>Next:&nbsp;<a href="ems_ca_me_md.html">Monopole and Dipole Terms&emsp;<small>[ems.ca.me.md]</small></a></li><li>Up:&nbsp;<a href="ems_ca_me.html">The Multipole Expansion&emsp;<small>[ems.ca.me]</small></a></li></ul>

  1795. <br>

  1796. <hr>

  1797. <div class="license">

  1798. <a rel="license noopener" href="https://creativecommons.org/licenses/by/4.0/"

  1799. target="_blank" class="m-2">

  1800. <img alt="Creative Commons License" style="border-width:0"

  1801. src="https://licensebuttons.net/l/by/4.0/80x15.png"/>

  1802. </a>

  1803. Except where otherwise noted, all content is licensed under a

  1804. <a rel="license noopener" href="https://creativecommons.org/licenses/by/4.0/"

  1805. target="_blank">Creative Commons Attribution 4.0 International License</a>.

  1806. </div>

  1807. <div id="postamble" class="status">

  1808. <p class="author">Author: Jean-Sébastien Caux</p>

  1809. <p class="date">Created: 2022-03-24 Thu 08:42</p>

  1810. <p class="validation"></p>

  1811. </div>

  1812. 

  1813. 

  1814. </div>

  1815. </html>