# Lab 1 CA ```EXPERIMENT #1
STUDY OF RC AND RL CIRCUITS
Venue: Instrumentation and Measurement Laboratory in E2
I.
INTRODUCTION
This laboratory is about verifying the transient behavior of RC and RL
circuits. You need to revise the natural and step response of RC and RL
circuits you have covered in lectures.
The charging and discharging of capacitor through a resistance is verified
first, finding out its theoretical value of time constant which is verified by
practical calculations.
The magnetizing and demagnetizing of a coil through a resistance is verified
first, finding out it’s the theoretical of its time constant which is verified by
practical calculations.
II.
PRE-LAB
Do the ORCAD simulations of both RC and RL circuits, calculate time constants and
plot the resulting waveforms across C (in the case of RC) and the waveform of the
current in the case of RL. In the ORCAD, use VPULSE as the Vs and set V1=5V,
V2=-5V, TD=0, TR=0, TF=0, PER=1/FREQUENCY and PW=0.5*PER
Use the following specifications while verifying the RC of Fig # in ORCAD
C1 0.001 uF
R1 3000 Ohm
Vs 10.0 Vpp
TYPE = SQUARE WAVE
FREQUENCY = 20 kHz
OFFSET = 0
Use the following specifications while verifying the RC of Fig # in PSPICE
L1 10 mH
R1 3000 Ohm
Vs 10.0 Vpp
TYPE = SQUARE WAVE
FREQUENCY = 20 kHz
OFFSET = 0
ECE Lab1 ECE 2201 SEMESTER I, 2007/2008
By Sheroz Khan
III.
EXPERIMENTAL METHOD
Equipment Required: Square-wave generator, discrete circuit components of
R1=3000Ω, L1=470uH and C1=1000pF, oscilloscope and square-wave
generator
Fig #1
Fig #2
IV.
Here derive the equation for the above vC(t) and vR(t), and plot them using
MATLAB to see if they are the same as the ones obtained PSPICE and the
oscilloscope in II and III respectively.
From the plots in II and III find out how long (in time constant, τ) does it take
for the vC(t) and vR(t) to get to 95 % of their maximum (or come down to 5 %
of minimum) of their minimum values.
Show with changing values of R, the resultant waveforms and effect on them.
V.
CONSLUSIONS
Varying R in RC circuit results in what?
Varying R in RL circuit results in what?
How much the voltage across a charged capacitor is reduced to after one time
constant, RC?
How much the voltage across a resistor in RL circuit is reduced to after one
time constant, L/R?
ECE Lab1 ECE 2201 SEMESTER I, 2007/2008
By Sheroz Khan
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