School of Electrical, Electronics and Computer Engineering EE101L/B6
Experiment 7 Forced and Natural Response of RC circuits with DC excitation
CORONEL, JLL!N "ER#L $% &roup No%' ( Date of )erformance' Fe*ruar+ , -.. Date of Su*mission' "arch -., -..
&rade
Engr% John "ercado /NS0RC0OR
/% O1JEC0/$ES
.%2 0o anal+3e the effect of energ+ storing de4ices li5e capacitors in DC circuits %2 0o demonstrate the charging and discharging response of a capacitor with DC excitation 6%2 0o 4erif+ the natural response and forced response of a DC excited RC circuit (%2 0o distinguish among the natural response, forced response and complete response of a d+namic RC circuit
//% D!0!70!1LES7&R!)8S Preliminary Data Sheet Experiment 7: Forced and Natural Response of RC circuits with DC excitation Name:Coronel, Jullan "er+l $% Crs/Sec: EE.-.L719 0a*le :%. Charging ;Complete response2 0ime ;ms2 $oltage;$ p<=-m$2 .- ;.2 .9> m$ - ;-2 6 m$ 6- ;62 >( m$ (- ;(-2 6-- m$ =- ;=2 6.9 m$ 9- ;9-2 6.9 m$ >- ;>-2 6( m$ .-- ;.--2 6( m$ .- ;.-2 6( m$ .(.9.>0a*le :% Discharging ;Natural response2 0ime ;ms2 $oltage ;m$2 6> .- ;.2 .:9 - ;-2 >( 6- ;62 ((- ;(-2 =- ;=-2 . 9- ;9-2 ( >- ;>-2 .-- ;.--2 .- ;.-2 .(.9.>-
ppro!ed "#:
Engr. John Mercado $nstructor
Date: Fe*ruar+ , -.. Group no: (
Charge .9%> μ 6% μ >%( μ 6- μ 6.%9 μ 6.%9 μ 6%( μ 6%( μ 6%( μ
Charge 6%> μ .:%9 μ >%( μ ( μ μ .% μ -%( μ -
///% /N0ER)RE0!0/ON
/n this experiment, we use oscilloscope to 5now the $oltage across the capacitor at specific time and its wa4eforms% Since, we 5now the 4oltage across the capacitor at specific time, and then we were a*le to 5now the 4alue of the charge of the capacitor at specific time% !s / o*ser4ed, *ased on m+ research, the resisti4e?capitance time constant is the time re@uired to charge a capacitor to approximatel+ 96A of the maximum 4oltage or to discharge a capacitor to approximatel+ 6:A of the initial 4oltage of the capacitor% Be use 0ina pro *ecause the amount of time re@uired to charge and discharge a capacitor is 4er+ small% /n RC circuit, it composed of a source, resistor and a capacitor% Be use resistor to control the charge and discharge time necessar+% /f the resistance of the resistor decreases, it ta5es less time to charge a capacitor% 1ecause of that, the amount of time of the capacitor to *ecome full+ charged is depends on the capacitances of the capacitor and the resistance of the resistor% 0he natural response of an RC circuit is the exponential part of the response that usuall+ dies out, due to the presence of capacitor in the circuit% 0herefore, this is the charging and discharging of the capacitor%
$% CONCLS/ON7S""!R#
!fter this experiment in Forced and Natural Response of RC circuits with DC excitation, / was a*le to 5now that when the 4oltage across a capacitor is not changing with time, the current through the capacitor is 3ero% 0herefore, / conclude that a capacitor is an open circuit to dc and that the 4oltage on a capacitor cannot change a*ruptl+ *ecause the capacitor resists an a*rupt change in the 4oltage across it% 8ere, / also conclude that capacitance is directl+ proportional to the area of the plates and in4ersel+ proportional to the distance *etween the plates of the capacitor% / also learned that the role of a capacitor is to store energ+% !dditionall+, / also conclude that natural response of an RC circuit is the circuits temporar+ response that will die out with time% 8ere, / conclude that forced response of an RC circuit is the *eha4ior of the circuit a long time after an external excitation is applied% !nd lastl+, complete response is the summation of all the response%
$/% REFERENCE7SORCES Electrical Circuits La*orator+ . "anual *+ 8ortinela and $allestero http'77www%ee%surre+%ac%u57)roects7C!L7complex?fre@uenc+7ForcedA-response%htm http'77www%m+oops%org7cocw7usu7ElectricalandComputerEngineering7SignalsandS+stems7 .9node9%html
/$% ES0/ONS !ND )RO1LE"S
1. What are the factors governing capacitance?
0he factors that go4ern capacitance are charge and 4oltage% !lso, the following can still include' surface area of the plates where the greater plate area the greater the capacitance whereas, the lesser the plate area the lesser the capacitance, distance *etween plates where the greater the plate spacing the lesser the capacitance whereas, the closer the plate spacing the greater the capacitance and permitti4it+ of material where the higher the permitti4it+ the greater the capacitance% 2. What are the characteristics of the capacitor when connected to a ! so"rce?
0he following are the characteristics of the capacitor in DC source' •
0he capacitor is an open circuit
•
! finite amount of energ+ can *e stored in a capacitor e4en if the current through it is 3ero%
•
! capacitor resists an a*rupt change in the 4oltage through it%
•
0he capacitor ne4er dissipates energ+ *ut onl+ stores it%
#. isc"ss $rief%& the different t&pes of capacitors •
Dielectric Capacitors are usuall+ of the 4aria*le t+pe such as used for tuning transmitters, recei4ers and transistor radios%
•
Film Capacitors are the most commonl+ a4aila*le of all t+pes of capacitors, consisting of a relati4el+ large famil+ of capacitors with the difference *eing in their dielectric properties%
•
Ceramic Capacitors or Disc Capacitors as the+ are g enerall+ called, are made *+ coating two sides of a small porcelain or ceramic disc with sil4er and are then stac5ed together to ma5e a capacitor%
•
Electrol+tic Capacitors are generall+ used when 4er+ large capacitance 4alues are re@uired%
'. What are the $asic app%ications of an (! circ"it?
0he *asic applications of an RC circuit are dela+ circuit and electronic flash unit% /t *asicall+ consists of an RC circuit with the capacitor c onnected in parallel with a neon lamp% ). efine the time constant of an (! circ"it?
0he time re@uired to charge a capacitor to 96 percent ;actuall+ 96% percent2 of full charge or to discharge it to 6: percent ;actuall+ 69%> percent2 of its initial 4oltage is 5nown as the 0/"E CONS0!N0 ;0C2 of the circuit% 6.
etermine the e*"iva%ence capacitance when a para%%e% with series connect
7.
and #0
capacitor is p%aced in
capacitors.
+ind the e*"iva%ent capacitance when series connected capacitors are connected in para%%e% with series connected capacitors.
and and
,. etermine the time constant of an (! circ"it with a resistance (- 200 hms and a )0 micro +arad capacitor connected in series with a 20 d! so"rce. τ =
τ =
9.
etermine the time constant of an (! circ"it with a resistance ( a capacitor connected in para%%e% with a #0 dc so"rce.
and
10.
etermine the vo%tage after ) after the switch is c%osed if the circ"it is connected to a #0 s"pp%& and the capacitor is initia%%& "ncharged.
(
