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Experiment: SERIES RC AND RL CIRCUITS

Experiment 2

SERIES RC AND RL CIRCUITS

I. OBJECTIVES

1. To become acquainted with phasor diagrams.2. To become familiar with series RC and RL circuits.

II. DISCUSSION:

Ohms law applies to all types of circuits but in the case of !C circuits all circuitquantities must be e"pressed as phasors. !ll calculations must be performed using phasor

algebra. ! phasor diagram can be used to represent these quantities. #ith this $ariables in

an !C circuit. The phasor diagram shows the magnitude and relati$e phase position of the

circuit quantities.

The circuit diagram of a series of a series RC circuit is shown in %igure 11.1a. The

current through the capacitor leads the $oltage across the capacitor by &'(. )ince the

same current passes through the capacitor and the resistor the $oltage across the resistor

leads the $oltage across the capacitor by &'(. This relationship is shown on the phasor

diagram of %igure 11.1b. %rom the phasor diagram er * e r + ,ec. %rom Ohms law we

ha$e- er * i er * iR and ec * i/c. %rom these equations we can compute for the

impedance of a series RC circuit. The impedance is gi$en by the equation * R + ,/c.

/c is the capaciti$e reactance and is equal to 0 fC where f and C are the frequency and

the capacitance respecti$ely.

The circuit diagram of a series RL circuit is shown in %igure 11.2a. The current

through the inductor lags the $oltage across it by &'(. )ince the same current flows

lectrical ngineering 3anel

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Experiment: SERIES RC AND RL CIRCUITS

through both elements the $oltage across the resistor lags the $oltage across the inductor

by &'(. This relationship is shown on the phasor diagram of %igure 11.2b. %rom the

phasor diagram we ha$e- eT* eR+ ,eL. %rom Ohmss law we ha$e- eT* i eR* iR and

eL* i/L. %rom which the total impedance of a series RL circuit is gi$en by *R 4 ,/L. 5f

frequency and inductance are 6nown we could compute for /L using the equation

/L* 2fL.

III. INSTRUMENTS AND COMPONENTS:

7O8

!C 7oltmeter 9:% Capacitor

!C !mmeter 1; 5nductor

Lamp 127 2.

2. Record the current and $oltages eRand ec.

>. =sing Ohms Law compute for the magniture of the impedance of the networ6.

Record it as the measured $alue.

9. Compute for the magnitude and phase angle of the impedance using the equation

* R + ,/c where /c * 1? 2fC.

. Record the current and the $oltages eRand eL.

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Experiment: SERIES RC AND RL CIRCUITS

9. =sing Ohms Law compute for the magnitude of the impedance of the networ6.

Record it as the measured $alue.

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Experiment: SERIES RC AND RL CIRCUITS

2. ! pure capacitor and a pure resistor are connected in series in an !C circuit. ! $oltmeter

reads >'7. when connected across the resistor. #hat will it read when connected across

bothA

>. ! current of 2.

to be equal. Calculate the $alue of the resistance and the inductance.

VIII. CONCLUSION:

lectrical ngineering 3anel