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Pengenalan Listrik Dan Rangkaian Listrik Maret 5, 2010

Filed under:Uncategorized ajiagus @ 12:17 pm

Electricit !utorial

!"is tutorial is a #rie$ introduction to t"e concepts o$ c"arge, %oltage, and current& !"is tutorialis not as long and tedious as a college te't#oo(, et it contains more in$ormation t"anstudents are li(el to )nd in an elementar sc"ool#oo(&

!"e *tom

* dra+ing o$ an atomn t"e le$t is a conceptual dra+ing o$ an atom& *toms are t"e #uilding#loc(s o$ matter& E%ert"ing is made o$ atoms, $rom roc(s, to trees, to stars, to e%en oursel$&*n atom consists o$ a tig"tl pac(ed nucleus containing one or more protons -colored red in

t"e picture., and usuall an e/ual num#er o$ neutrons -gra.& Electrons -#lue. surround t"enucleus, $orming an electron cloud& !"e num#er o$ electrons in an electricall sta#le atom isal+as e/ual to t"e num#er o$ protons in t"e nucleus&

Electric "arge

pposite c"arges attract& i(e c"arges repel& * curious t"ing "appens #et+een protons andelectrons: a proton and an electron are al+as attracted to one anot"er, +"ile a proton +illrepel ot"er protons, and an electron +ill repel ot"er electrons& !"is #e"a%ior is caused #somet"ing called t"e electric $orce& rotons are said to "a%e a positi%e electric c"arge, +"ileelectrons "a%e a negati%e electric c"arge& !+o o#jects +it" t"e same tpe o$ c"arge pus"a+a $rom eac" ot"er, +"ile t+o o#jects +it" opposite c"arges attract to eac" ot"er& 3ince aproton and an electron "a%e opposite electric c"arges, t"e are attracted to eac" ot"er& !+oprotons, "o+e%er, mo%e a+a $rom eac" ot"er #ecause o$ t"eir e/ual electric c"arges& !"esame is true o$ t+o electrons, +"ic" pus" a+a $rom eac" ot"er #ecause o$ t"eir e/ual

negati%e c"arges&Electric 4alance

Electric #alance Most matter contains an e/ual num#er o$ protons and electrons& !"e negati%eelectrons #alance out t"e positi%e protons, and t"e matter "as no o%erall electrical c"arge& !"e+ord o%erall is important, since t"e c"arges are still t"ere, #ouncing around inside t"e matter&Electrical c"arges are e%er+"ere, #ut +e just cant sense t"em #ecause t"e are in #alance&6n $act, i$ ou ta(e c"emistr, oull learn t"at t"e electric $orce is t"e %er t"ing t"at "oldsmatter toget"er& !"e ne't time ou pic( somet"ing up, just t"in( t"at +"ate%er ou are"olding is literall )lled +it" electric c"arge& !"is is an important $act t"at man people miss+"en t"e stud electricit&3tatic Electricit

* dra+ing o$ t+o ions ets sa +e steal an electron $rom one atom and gi%e t"e electron toanot"er atom& ne atom +ill "a%e an o%erall positi%e c"arge and t"e ot"er +ill "a%e an o%erallnegati%e c"arge& "en t"is "appens, t"e t+o atoms are called ions& 4ecause ions "a%e an

o%erall electric c"arge, t"e can interact +it" ot"er c"arged o#jects& 3ince li(e c"arges repeland opposite c"arges attract, a positi%e ion +ill attract negati%el c"arged o#jects, suc" aselectrons or ot"er ions, and +ill repel positi%el c"arged o#jects& * negati%el c"arged ion +illattract positi%el c"arged o#jects, and +ill repel ot"er negati%el c"arged o#jects&

!"e same is true $or larger o#jects& 6$ ou ta(e electrons $rom one o#ject and place t"em onanot"er o#ject, t"e )rst o#ject +ill "a%e an o%erall positi%e c"arge +"ile t"e second +ill "a%ean o%erall negati%e c"arge& 8epending on t"e tpes o$ o#jects and t"e amount o$ c"argein%ol%ed, t"e electric $orce ma #e enoug" to cause t"e o#jects to stic( toget"er& !"isp"enomenon is o$ten re$erred to as 9static electricit&

!"ere are se%eral +as to steal electrons $rom one o#ject and gi%e t"em to anot"er& 3ome o$t"e +as include c"emical reactions, mec"anical motion, lig"t, and e%en "eat& 6$ ou ru# aglass rod +it" sil(, t"e electrons in t"e glass rod +ill #e (noc(ed o; and collected on t"e sil(&

!"e glass rod gains an o%erall positi%e c"arge, and t"e sil( gains an o%erall negati%e c"arge& 6n

a #atter, c"emical reactions are used to $orce electrons $rom t"e positi%e terminal and placet"em on t"e negati%e terminal&Measuring "arges
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!"e amount o$ o%erall electric c"arge possessed # an o#ject is measured in coulom#s& necoulom# is roug"l e/ual to t"e amount o$ c"arge possessed # o+& *n electric current is not"ing more t"an t"e >o+ o$ electric c"arges&Electric c"arges can onl >o+ t"roug" certain materials, called conductors& *lt"oug" t"eelectrons in most materials are con)ned to )'ed or#its, some materials, including most metals,"a%e man loose electrons +"ic" are $ree to +ander around t"roug" t"e material& Materials+it" t"is propert act as conductors& "en a conductor is placed #et+een t+o c"argedo#jects, t"ese loose electrons are pus"ed a+a # t"e negati%el c"arged o#ject and aresuc(ed into t"e positi%el c"arged o#ject& !"e result is t"at t"ere is a >o+ o$ c"arge, called a

current, and t"e t+o o#jects c"arges #ecome #alanced& !"e amount o$ current >o+ingt"roug" a conductor at an gi%en time in measured in amperes, or amps $or s"ort& "en ouread t"at somet"ing uses so man amps, +"at ou are #eing told is t"e amount o$ current>o+ing t"roug" t"e de%ice& ne ampere is e/ual to t"e >o+ o$ one coulom# o$ c"arge in onesecond&4atteries and urrent

4atteries and current 6n t"e pre%ious paragrap", +e loo(ed at "o+ current >o+s $rom onec"arged o#ject to anot"er, canceling out t"e c"arges o$ t"e t+o o#jects& nce t"e c"arges+ere canceled, t"e current stopped& 6$ current +ere al+as t"is s"ort?li%ed, it +ould #e %erimpractical& 6magine a >as"lig"t t"at onl lasted a $raction o$ a second #e$ore needing to #erec"argedJ "ile current does tend to cancel out c"arges on t+o o#jects and t"en stop>o+ing, i$ a c"arge can #e placed on t"e o#jects $aster t"an t"e current can drain t"e c"arge,it is possi#le to (eep a current >o+ing inde)nitel& !"at is +"at "appens in a #atter& "emicalreactions +it"in t"e #atter pump electrons $rom t"e positi%e terminal to t"e negati%e terminal

$aster t"an t"e de%ice connected to t"e #atter can drain t"em& !"e #atter +ill continue tosuppl as muc" current as t"e de%ice re/uires until t"e c"emicals +it"in t"e #atter are used


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up, at +"ic" point t"e #atter is dead and must #e replaced&Kesistance

*ll conductors o;er some degree o$ resistance to t"e >o+ o$ electric current& "at "appens ist"is: *s electrons tra%el t"roug" t"e conductor, t"e #ump into atoms, losing some o$ t"eirmo%ement in jiggling t"e atom& !"e result is t"at t"e current >o+ing t"roug" t"e conductor isslo+ed do+n, and t"e conductor is "eated& !"e amount t"at a gi%en conductor resists t"e >o+o$ electric current is measured in o"ms&o+er

"ene%er current >o+s, +or( is done& * conductor ma #e "eated, a motor ma #e spun, a#ul# mig"t gi%e o; lig"t, or some ot"er $orm o$ energ ma #e released& !"ere is a simple la+t"at tells e'actl "o+ muc" +or( ma #e done # a >o+ing current& !"e amount o$ +or( doneis e/ual to t"e %oltage o$ t"e suppl times t"e current >o+ing t"roug" t"e +ire& !"is la+ ise'pressed in t"e $orm B6H, +"ere is t"e po+er in +atts, 6 is t"e current in amps, and H ist"e %oltage in %olts& For e'ample, i$ +e )nd t"at a lig"t #ul# dra+s "al$ o$ an amp at 120 %olts,+e simpl multipl t"e 120 %olts # "al$ an amp to )nd t"at t"e #ul# dra+s o+s, t"e circuit is said to #e 9closed, and t"e lamp +ill lig"t& !"ecurrent >o+s $rom t"e cell along one +ire to t"e lamp, t"roug" t"e lamp, and along t"e ot"er+ire #ac( to t"e cell& "en t"e +ires are disconnected, t"e circuit is said to #e 9open or9#ro(en& 6n practice, circuits are opened # suc" de%ices as s+itc"es, $uses, and circuit#rea(ers -see $use, electricN circuit #rea(erN s"ort circuit.& !+o general circuit classi)cations are

series and parallel& !"e elements o$ a series circuit are connected end to endN t"e samecurrent >o+s t"roug" its parts one a$ter anot"er& !"e elements o$ a parallel circuit areconnected so t"at eac" component "as t"e same %oltage across its terminalsN t"e current >o+is di%ided among its parts& "en t+o circuit elements are connected in series, t"eir e;ecti%eresistance -impedance i$ t"e circuit is #eing $ed alternating current. is e/ual to t"e sum o$ t"eseparate resistancesN t"e current is t"e same in eac" component t"roug"out t"e circuit& "encircuit elements are connected in parallel, t"e total resistance is less t"an t"at o$ t"e element"a%ing t"e least resistance, and t"e total current is e/ual to t"e sum o$ t"e currents in t"eindi%idual #ranc"es& * #atter?po+ered circuit is an e'ample o$ a direct?current circuitN t"e%oltages and currents are constant in magnitude and do not %ar +it" time& 6n alternating?current circuits, t"e %oltage and current periodicall re%erse direction +it" time& * standardelectrical outlet supplies alternating current& ig"ting circuits and electrical mac"iner usealternating current circuits& Man ot"er de%ices, including computers, stereo sstems, andtele%ision sets, must )rst con%ert t"e alternating current to direct current& !"at is done # a

special internal circuit usuall called a po+er suppl& * digital circuit is a special (ind o$electronic circuit used in computers and man ot"er de%ices& Magnetic circuits are analogousto electric circuits, +"ere magnetic materials are regarded as conductors o$ magnetic >u'&Magnetic circuits can #e part o$ an electric circuitN a trans$ormer is an e'ample& E/ui%alentcircuits are used in circuit analsis as a modeling toolN a simple circuit made up o$ a resistor,and an inductor mig"t #e used to electricall represent a loudspea(er& Electrical circuits canalso #e used in ot"er )elds o$ studies& 6n t"e stud o$ "eat >o+, $or e'ample, a resistor is usedto represent t"ermal insulation& perating electric circuits can #e used $or general pro#lemsol%ing -as in an analog computer.&Oirc""o;s la+s

Oirc""o;s la+s P$or Qusta% K& Oirc""o;R, pair o$ la+s stating general restrictions on t"e currentand %oltage in an electric circuit& !"e )rst o$ t"ese states t"at at an gi%en instant t"e sum o$t"e %oltages around an closed pat", or loop, in t"e net+or( is zero& !"e second states t"at atan junction o$ pat"s, or node, in a net+or( t"e sum o$ t"e currents arri%ing at an instant ise/ual to t"e sum o$ t"e currents >o+ing a+a&inductance


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inductance, /uantit t"at measures t"e electromagnetic induction o$ an electric circuitcomponentN it is a propert o$ t"e component itsel$ rat"er t"an o$ t"e circuit as a +"ole& !"esel$?inductance, , o$ a circuit component determines t"e magnitude o$ t"e electromagnetic$orce -em$. induced in it as a result o$ a gi%en rate o$ c"ange o$ t"e current t"roug" t"ecomponent& 3imilarl, t"e mutual inductance, M, o$ t+o components, one in eac" o$ t+oseparate #ut closel located circuits, determines t"e em$ t"at eac" ma induce in t"e ot"er $ora gi%en current c"ange& 6nductance is e'pressed in "enrs -$or =osep" enr.& *n inductor is a

de%ice designed to produce an inductance, e&g&, a coilN an ideal inductor, i&e&, one "a%ing noresistance or capacitance -see impedance., is o$ten called an inductance&u(um "m menata(an #a"+a #esar arus ang mengalir pada suatu (ondu(tor pada su"utetap se#anding dengan #eda potensial antara (edua ujung?ujung (ondu(tor6 B H C K

UOUM M U!UO K*QO*6* !EK!U!U

6 B n EK S n rd

6 B nK S rdCp

n B #ana( elemen ang disusun seriE B ggl -%olt.rd B "am#atan dalam elemenK B "am#atan luarp B #ana(na elemen ang disusun paralel

K*QO*6* *M4*!* 863U3U 3EK6 8* *K*E3EK6

K B K1 S K2 S KT S H B H1 S H2 S HT S 6 B 61 B 62 B 6T B

*K*E

1 B 1 S 1 S 1K K1 K2 KT

H B H1 B H2 B HT B 6 B 61 S 62 S 6T S

EEKQ6 8* 8*V* 63!K6O

EEKQ6 63!K6O -.adala" energi ang dipa(ai -terserap. ole" "am#atan K&

B H 6 t B HWtCK B 6WKt

=oule B att&deti(O B Oilo&att&jam

8*V* 63!K6O -. adala" energi listri( ang terpa(ai setiap deti(&

B Ct B H 6 B HWCK B 6WK

UOUM O6KFF 6 : jumla" arus menuju suatu titi( ca#ang sama dengan jumla" arus angmeninggal(anna&

3 6in B 6out

UOUM O6KFF 66 : dalam rang(aian tertutup, jumla" alja#ar QQ -e. dan jumla" penurunanpotensial sama dengan nol&

3e B 3 6K B 0

**! UOUK 63!K6O !EK86K6 8*K61& =EM4*!* E*!3!E

diguna(an untu( mengu(ur nilai suatu "am#atan dengan cara mengusa"a(an arus angmengalir pada gal%anometer B nol -(arena potensial di ujung?ujung gal%anometer sama#esar.& =adi #erla(u rumus per(alian silang "am#atan :

K1 KT B K2 K'2& *MEKME!EK

untu( memper#esar #atas u(ur ampermeter dapat diguna(an "am#atan 3"unt -Ks. angdipasang sejajarCparalel pada suatu rang(aian&

Ks B rd 1C-n?1.n B pem#esaran pengu(uranT& H!ME!EK


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untu( memper#esar #atas u(ur %oltmeter dapat diguna(an "am#atan multiplier -K?. angdipasang seri pada suatu rang(aian& 8alam "al ini K& "arus dipasang di depan %oltmeterdipandang dari datangna arus listri(&

Km B -n?1. rdn B pem#esaran pengu(uran

!EQ*Q* =E6! -H. :

adala" #eda potensial antara (utu#?(utu# sum#er atau antara dua titi( ang diu(ur&1& 4ila #atere mengalir(an arus ma(a tegangan jepitna adala":Ha# B e X 6 rd

2& 4ila #atere menerima arus ma(a tegangan jepitna adala":Ha# B e S 6 rd

T& 4ila #atere tida( mengalir(an atau tida( menerima arus ma(ategangan jepitna adala" &Ha# B e

8alam menelesaian soal rang(aian listri(, perlu diper"ati(an :

1& am#atan K ang dialiri arus listri(& am#atan K dia#ai(an ji(a tida(dilalui arus listri(&

2& am#atan K umumna tetap, se"ingga le#i" cepat mengguna(an

rumus ang #er"u#ungan dengan "am#atan K terse#ut&T& Kumus ang sering diguna(an: "u(um "m, "u(um Oirc"o;, si$atrang(aian, energi dan daa listri(&

onto" 1 :

Untu( rang(aian seperti pada gam#ar, #ila sa(lar 31 dan 32 ditutup ma(a "itungla"penunju((an jarum %oltmeter J

=a+a# :

Oarena sa(lar 31 dan 32 ditutup ma(a K1, K2, dan KT dilalui arus listri(, se"ingga :1 B 1 S 1Kp K2 KT

Kp B K2 KT B 2K2 S K1

H B 6 K B 6 -K1 S Kp.6 B 2AC-TS2. B A& *

Holtmeter mengu(ur tegangan di K2 di KT, dan di ga#ung(an K2 CC KT, jadi :

H B 62 K2 B 6T KT B 6 KpH B 6 Kp B 0, H

onto" 2:

ada lampu * dan 4 masing?masing tertulis 100 +att, 100 %olt& Mula?mula lampu * den 4di"u#ung(an seri dan dipasang pada tegangan 100 %olt, (emudian (edua lampu di"u#ung(anparalel dan dipasang pada tegangan 100 %olt& !entu(an per#andingan daa ang dipa(ai pada"u#ungan paralel ter"adap seri Jam#atan lampu dapat di"itung dari data ang tertulis dilampu :K* B K4 B HWC B 100WC100 B 100

Untu( lampu seri : K3 B K* S K4 B 200 Untu( lampu paralel : Kp B K* G K4 B 50 K* S K4

Oarena tegangan ang terpasang pada masing?masing rang(aian sama ma(a guna(an rumus : B HWCK

=adi per#andingan daa paralel ter"adap seri adala" :p B HW : HW B Ks B As Kp Ks Kp 1

onto" T:

8ua #ua" #atere ujung?ujungna ang sejenis di"u#ung(an, se"ingga mem#entui( "u#unganparalel& Masing?masing #atere memili(i QQ 1,5 HN 0,T o"m dan 1 HN 0,T o"m&itungla"tegangan #ersama (edua #atere terse#ut J

=a+a# :


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!enta(an ara" loop dan ara" arus listri( -li"at gam#ar., dan terap(an "u(um Oirc"o; 66,3e S 3 6 K B 0e1 S e2 B 6 -r1 S r2.

6 B -1,5 X 1. B 5 *0,T S 0,T

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