DE LA SALLE LIPA
COLLEGE OF INFORMATION TECHNOLOGY AND ENGINEERING
ELECTRICAL ENGINEERING DEPARTMENT
CKTS002 – CIRCUITS 2 LABORATORY EXPERIMENT MANUAL
EXPERIMENT #1: SERIES RC AND RL CIRCUITS
I.
OBJECTIVES
1. To analyze the phasor relationships of voltage and current for RC circuit.
2. To analyze the phasor relationships of voltage and current for RL circuit.
II.
DISCUSSION
Ohm’s law applies to all types of circuits, but in the case of AC circuits all
currents, voltages, reactances, resistances, and impedances must be
expressed as phasors. All calculations must be done vectorially with
reference to a phasor diagram. All phasor diagrams should be accompanied
by a circuit diagram. If this is not done, then such a circuit diagram must be
obvious or assumed in order to interpret the phasor diagram. The phasor
diagram shows only the magnitude and relative phase angles of the currents
and voltages while the circuit diagram shows only the location, direction and
polarity of the currents and voltages. These are important distinctions and
confusion generally results when not recognized or when the two diagrams
are combined.
The circuit diagram of a series RC circuit is shown in Fig. 1.1a. The
current through a capacitor leads the voltage across it by 90 degrees. Since
the same current flows through the capacitor as flows through the resistor and
since the voltage across the resistors in phase with the current through it, we
may conclude that the voltage across the resistor leads the voltage across the
capacitor by 90 degrees. This relationship is shown as the phasor diagram in
Fig. 2.1b. From the phasor diagram, ET = ER – jEC. We observe that from
Ohm’s law, we have: ET = IZ, ER = IR and EC = IXc. From these equations, we
can compute the impedance of a series RC circuit. The impedance is given
by the equation, Z = R - jXC. Xc can be computed if frequency and
capacitance are known by the equation Xc = ½ π f C.
The circuit diagram of a series RL circuit is shown in Fig. 1.2a. The current
through the inductor lags the voltage across it by 90 degrees. Since the same
current flows through both elements, the voltage across the resistor lags that
across the inductor by 90 degrees. The phasor diagram showing these
voltages is given below. From the phasor diagram, we have: E T = ER + jEL.
We know from Ohm’s law that ET = IZ, ER = IR and EL = IXL. From which the
total impedance of the series RL circuit is given by Z = R + jXL. If frequency
and inductance are known, we could compute for XL using the equation XL=
2 π f L.
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DE LA SALLE LIPA
COLLEGE OF INFORMATION TECHNOLOGY AND ENGINEERING
ELECTRICAL ENGINEERING DEPARTMENT
CKTS002 – CIRCUITS 2 LABORATORY EXPERIMENT MANUAL
(a) circuit diagram
(b) phasor diagram
Fig. 1.1 Series RC circuit
(b) circuit diagram
(b) phasor diagram
Fig. 1.2 Series RL circuit
III.
COMPONENTS NEEDED
ITEM NO.
IV.
DESCRIPTION
AC voltmeter
AC ammeter
Lamp (10 Ω)
50 H inductor
0.15 F capacitor
12V AC Power Supply
PROCEDURE
RC circuit:
1. Connect the circuit shown in Fig. 1.3.
2. Set the AC power supply to 12V, 0.1 Hz.
3. Record the current I and voltages ER and EC.
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QUANTITY
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1
1
1
1
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DE LA SALLE LIPA
COLLEGE OF INFORMATION TECHNOLOGY AND ENGINEERING
ELECTRICAL ENGINEERING DEPARTMENT
CKTS002 – CIRCUITS 2 LABORATORY EXPERIMENT MANUAL
4. Using Ohm’s law, compute the magnitude of the impedance network.
Record it as the measured value.
5. Compute the magnitude and phase angle of the impedance using the
equation Z = R - jXC where XC = 1/ 2 π fC.
6. Compute the percentage difference between the measured and compared
value of the impedance.
RL circuit:
1.
2.
3.
4.
Connect the circuit shown in Fig. 1.4.
Set the AC power supply to 12V, 0.1 Hz.
Record the current I and voltages ER and EL.
Using Ohm’s law, compute the magnitude of the impedance network.
Record it as the measured value.
5. Compute the magnitude and phase angle of the impedance using the
equation Z = R + jXL where XL = 2 π fL.
6. Compute the percentage difference between the measured and compared
value of the impedance.
V.
CIRCUIT DIAGRAM
Fig 1.3. Capacitive circuit
Fig 1.4. Inductive circuit
VI.
DATA AND RESULTS
CIRCUIT
ET
I
ER
EC
Series RC
Series RL
3
EL
Z
(meas)
Z
(comp)
% diff
Ɵ
(comp)
DE LA SALLE LIPA
COLLEGE OF INFORMATION TECHNOLOGY AND ENGINEERING
ELECTRICAL ENGINEERING DEPARTMENT
CKTS002 – CIRCUITS 2 LABORATORY EXPERIMENT MANUAL
VII.
QUESTIONS
1. A circuit contains a fixed resistor in series with variable capacitor. Plot the curve
to show the variation of the impedance with capacitive reactance as the
capacitance is varies from zero to an infinitely large value.
2. A pure capacitor and pure resistor are connected in series in an AC circuit. A
voltmeter reads 30 V when connected across the capacitor and 40 V when
connected across the resistor. What will it read when connected across both?
3. A current of 25 A is observed in 120 V 60 Hz circuit which consist of a pure
resistor and a pure inductor in series. The voltages across the resistor and
inductor are found to be identical. Calculate the value of the resistance and the
inductance.
VIII.
CONCLUSION
References:
Electrical Engineering Department: Laboratory Experiment Manual - Electrical Circuits 2
Online Resources:
https://phet.colorado.edu/sims/html/circuit-construction-kit-ac/latest/circuit-constructionkit-ac_en.html
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