Inductors in DC Circuits

Add Abstract, Introduction and Conclusion to the Inductors in DC Circuits Lab. Input calculation

Electric Circuits Lab

Instructor: ———–

Lab

Inductors in DC Circuits

Student Name(s):

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Honor Pledge:

I pledge to support the Honor System of ECPI. I will refrain from any form of academic dishonesty or deception, such as cheating or plagiarism. I am aware that as a member of the academic community, it is my responsibility to turn in all suspected violators of the honor code. I understand that any failure on my part to support the Honor System will be turned over to a Judicial Review Board for determination. I will report to the Judicial Review Board hearing if summoned.

Date: 1/1/2018

Contents
Abstract 3
Introduction 3
Procedures 3
Data Presentation & Analysis 4
Calculations 4
Required Screenshots 4
Conclusion 4
References 5

Abstract

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What is an Abstract?

This should include a brief description of all parts of the lab. The abstract should be complete in itself. It should summarize the entire lab; what you did, why you did it, the results, and your conclusion. Think of it as a summary to include all work done. It needs to be succinct yet detailed enough for a person to know what this report deals with in its entirety.

Objectives of Week 2 Lab 1:

· Measure the resistance and Inductance.
· Use the Oscilloscope and Function generator.
· Measure the LR time constant using VR and VL.
· Understand the effect of series and parallel inductors on LR time constant.

Introduction

(This instruction box is to be deleted before submission of the Lab report)

What is an Introduction?

In your own words, explain the reason for performing the experiment and give a concise summary of the theory involved, including any mathematical detail relevant to later discussion in the report. State the objectives of the lab as well as the overall background of the relevant topic.

Address the following items in your Introduction:

· What is the time constant for an RL circuit and what is its significance?
· How do inductors combine in series? (Give formula)
· How do inductors combine in parallel? (Give formula)
· What is inductive reactance? (Give formula)

Procedures

1.
Construct the circuit shown in Figure 1 in Multisim. (You may either use the clock voltage of the function generator.)

Figure 1: RL Circuit

2.
Connect Channel A of the oscilloscope across the resistor and Channel B across the inductor.

3.
Set the voltage source to
5VPP; 300 Hz, Square wave, 50% duty cycle

4. You should be able to see the waveform as shown below. (Use Volts/Div and Time/DIV settings to adjust the signal)

Figure 2. Voltage across the inductor and resistor

5.
Calculate the time constant of an LR circuit. Record the result in
Table 1 below under the calculated value.

 = L/R

6

. Turn on the cursors on the oscilloscope

7.
Measuring the time constant with VL: (shown in figure 3)

i.

Set Channel A to “0” to turn off Channel A signal.

ii.
Measure the peak value of the voltage across the resistor, by placing one of the cursors at the peak point _________.

iii.
Calculate the 37% of the above value _________.

iv.
Place the second cursor at the voltage calculated above in step (iii).

v.
Observe the change in time (T2-T1) value on the scope, which is the value of one time constant.

vi.
Record the T2-T1 value in
Table 1 under measured value using VL.

Figure 3: Measuring RL time constant using VL example (L = 150 mH)

Note: your scope screen will be different

8.
Set Channel B to “0” to turn it off.

9.
Set Channel A to “AC”

10. Adjust the Trigger settings, if needed, and you should be able to see the waveform as shown below. (Use Volts/Div and Time/DIV knobs to adjust the signal)

Figure 4: Voltage across the resistor

11.
Measuring the time constant: (shown in figure 5)

i.

Measure the peak value of the signal, by placing one of the cursors (T1) at the peak point and the other cursor (T2) at the negative peak.
Calculate the total peak-to-peak voltage (T1-T2) _________.

ii.
Calculate the 63% of the above value _________.

iii.
Place the second cursor (T2) at the negative peak value plus the step (ii) value above
.

iv.
Place T1 at the negative peak just before the signal begins to rise.

vii.
Observe the dT (T2-T1) value on the scope, which is one time constant.

viii.
Record the result in
Table 1 above under measured value using VR.

Figure 5: Measuring RL time constant using VR example (L = 150 mH)

Note: your scope screen will be different

Part II:

12.
Place two inductors in series as shown below.

Figure 6: Series Inductors

13.
Calculate the total inductance value and record the results in
Table 2 (Calculated) below.

14.

Measure the total inductance value. (If you have the proper measuring device to do so). Use the following procedure to measure the inductance in Multisim if you do not have the proper measuring device.

i.
Connect the Impedance Meter (Simulate >>Instruments>>LabView Instruments>>Impedance Meter) as shown in
Figure 7.

ii.
Measure the inductive reactance, XL, as shown in
Figure 7

.

iii.
Calculate the inductance using the equation. and record the value in
Table 2 (Measured).

Figure 7. Impedance Meter in Multisim Example

15.
Build the circuit in
Figure 9.

Figure 8: RL circuit with series Inductors

16.
Calculate the new LR time constant. Record the result in
Table 3 below.

17.
Connect Channel A of the oscilloscope across the resistor.

18. Adjust the Trigger, if needed, and you should be able to see the waveform as shown below. (Use Volts/Div and Time/DIV knobs to adjust the signal)

Figure 9: Voltage across the resistor

19. Use the cursors on the oscilloscope to
measure the time constant (refer to step 11). Record the result in
Table 3 below under measured value.

Part III:

20.
Place two inductors in parallel as shown below. (
Note: The 0.001 Ω resistor is
ONLY required for simulation in Multisim. Without the resistor, the mathematical model will not converge.)

Figure 10: Parallel Inductors

21.
Calculate the total inductance value and record the results in
Table 4
(Calculated).

22.
Measure the total parallel inductance value. (If you have the proper device to do so). Use the following procedure to measure the inductance in Multisim if you do not have the proper measuring device.

i.
Connect the Impedance Meter (Simulate >>Instruments>>LabView Instruments>>Impedance Meter).

ii.
Measure the inductive reactance, XL
.

iii.
Calculate the inductance using the equation and record the value in
Table 4 (Measured).

23.
Build the following circuit. (
Note: The 0.001 Ω resistor is
ONLY required for simulation in Multisim. Without the resistor, the mathematical model will not converge.)

Figure 11: RL circuit with parallel Inductors

24.
Calculate the new LR time constant. Record the result in
Table 5.

25.
Connect Channel A of the oscilloscope across the resistor.

26. You should be able to see the waveform as shown below. (Use Volts/Div and Time/DIV knobs to adjust the signal)

Figure 12: Voltage across the resistor

27. Use the cursors on the oscilloscope to
measure the time constant (refer to step 11). Record the result in
Table 5 under measured value.

Data Presentation & Analysis

Calculated value

Measured value using VL

Measured value using VR

Time constant ()

Table 1: Calculated and measured time constant values

Calculated Value

Measured Value

Inductance

Table 2: Series Inductors

Calculated value

Measured value using VR

Time constant ()

Table 3: Calculated and measured time constant values

Calculated value

Measured value

Inductance

Table 4: Parallel Inductors

Calculated value

Measured value using VR

Time constant ()

Table 5: Calculated and measured time constant values

Calculations

(This instruction box is to be deleted before submission of the Lab report)
Show all of your calculations in this section.

Part 1 step 5:  =

Part 2 step 13: LT =

Part 2 step 14: LT =

Part 2 step 16:  =

Part 3 step 21: LT =

Part 3 step 22: LT =

Part 3 step 24:  =

Required Screenshots

(This instruction box is to be deleted before submission of the Lab report)

Place screenshots of measurements in this section. You may change the names of the figures as the ones provided show the required content.

Figure 13: Screenshot of Waveforms Part 1 Step 4

Figure 14: Screenshot of Waveforms Part 1 Step 7

Figure 15: Screenshot of Waveforms Part 1 Step 11

Figure 16: Screenshot of Impedance Measurement Part 2 Step 14

Figure 17: Screenshot of Waveforms Part 2 Step 19

Figure 18: Screenshot of Impedance Measurement Part 3 Step 22

Figure 19: Screenshot of Waveforms Part 3 Step 27

Conclusion

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What is a Conclusion?

This section should reflect your understanding of the experiment conducted. Important points to include are a brief discussion of your results, and an interpretation of the actual experimental results as they apply to the objectives of the experiment set out in the introduction should be given. Also, discuss any problems encountered and how they were resolved.

Address the following in your conclusions:
· Did your measured results match your calculated values? If not, why not?
· What happened to the overall inductance when you went from one series inductors to two? (Did inductance increase or decrease?)
· What happened to the overall inductive reactance when you went from one series inductor to two? (Did the inductive reactance increase or decrease?)
· What happened to the time constant when you went from one series inductor to two? (Did the time constant increase or decrease?)
· What happened to the overall inductance when you went from one inductor to two parallel inductors? (Did the inductance increase or decrease?)
· What happened to the overall inductive reactance when you went from one inductor to two parallel inductors? (Did the inductive reactance increase or decrease?)
· What happened to the time constant when you went from one inductor to two parallel inductors? (Did the time constant increase or decrease?)

References

Floyd, T. L., & Buchla, D. M. (2019). 
Principles of Electric Circuits (10th Edition). Pearson Education (US). 

https://bookshelf.vitalsource.com/books/9780134880068

(2017) National Instruments Multisim (V 14.1) [Windows]. Retrieved from

http://www.ni.com/multisim/

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ELECTRIC CIRCUITS I

METRIC PREFIX TABLE

Metric

Prefix

Symbol

Multiplier

(Traditional Notation)

Expo-

nential

Description

Yotta

Y

1,000,000,000,000,000,000,000,000

1024

Septillion

Zetta

Z

1,000,000,000,000,000,000,000

1021

Sextillion

Exa

E

1,000,000,000,000,000,000

1018

Quintillion

Peta

P

1,000,000,000,000,000

1015

Quadrillion

Tera

T

1,000,000,000,000

1012

Trillion

Giga

G

1,000,000,000

109

Billion

Mega

M

1,000,000

106

Million

kilo

k

1,000

103

Thousand

hecto

h

100

102

Hundred

deca

da

10

101

Ten

Base

b

1

100

One

deci

d

1/10

10-1

Tenth

centi

c

1/100

10-2

Hundredth

milli

m

1/1,000

10-3

Thousandth

micro

µ

1/1,000,000

10-6

Millionth

nano

n

1/1,000,000,000

10-9

Billionth

pico

p

1/1,000,000,000,000

10-12

Trillionth

femto

f

1/1,000,000,000,000,000

10-15

Quadrillionth

atto

a

1/1,000,000,000,000,000,000

10-18

Quintillionth

zepto

z

1/1,000,000,000,000,000,000,000

10-21

Sextillionth

yocto

y

1/1,000,000,000,000,000,000,000,000

10-24

Septillionth

4-BAND RESISTOR COLOR CODE TABLE

BAND

COLOR

DIGIT

Band 1: 1st Digit

Band 2: 2nd Digit

Band 3: Multiplier
(# of zeros
following 2nd digit)

Black

0

Brown

1

Red

2

Orange

3

Yellow

4

Green

5

Blue

6

Violet

7

Gray

8

White

9

Band 4: Tolerance

Gold

± 5%

SILVER

± 10%

5-BAND RESISTOR COLOR CODE TABLE

BAND

COLOR

DIGIT

Band 1: 1st Digit

Band 2: 2nd Digit

Band 3: 3rd Digit

Band 4: Multiplier
(# of zeros
following 3rd digit)

Black

0

Brown

1

Red

2

Orange

3

Yellow

4

Green

5

Blue

6

Violet

7

Gray

8

White

9

Gold

0.1

SILVER

0.01

Band 5: Tolerance

Gold

± 5%

SILVER

± 10%

EET Formulas & Tables Sheet

Page
1 of
21

UNIT 1: FUNDAMENTAL CIRCUITS

CHARGE

Where:
Q = Charge in Coulombs (C)
Note:
1 C = Total charge possessed by 6.25×1018 electrons

VOLTAGE

Where:
V = Voltage in Volts (V)
W = Energy in Joules (J)
Q = Charge in Coulombs (C)

CURRENT

Where:
I = Current in Amperes (A)
Q = Charge in Coulombs (C)
t = Time in seconds (s)

OHM’S LAW

Where:
I = Current in Amperes (A)
V = Voltage in Volts (V)
R = Resistance in Ohms (Ω)

RESISTIVITY

Where:
ρ = Resistivity in Circular Mil – Ohm per Foot (CM-Ω/ft)
A = Cross-sectional area in Circular Mils (CM)
R = Resistance in Ohms (Ω)
ɭ = Length in Feet (ft)
Note:
CM: Area of a wire with a 0.001 inch (1 mil) diameter

CONDUCTANCE

Where:
G = Conductance in Siemens (S)
R = Resistance in Ohms (Ω)

CROSS-SECTIONAL AREA

Where:
A = Cross-sectional area in Circular Mils (CM)
d = Diameter in thousandths of an inch (mils)

ENERGY

Where:

W = Energy in Joules (J). Symbol
is an italic
W.

P = Power in Watts (W). Unit
is not an italic W.

t = Time in seconds (s)
Note:
1 W = Amount of power when 1 J of energy
is used in 1 s

POWER

Where:
P = Power in Watts (W)
V
= Voltage in Volts (V)

I = Current in Amperes (A)
Note:
Ptrue = P in a resistor is also called true power

OUTPUT POWER

Where:
POUT = Output power in Watts (W)
PIN = Input power in Watts (W)
PLOSS = Power loss in Watts (W)

POWER SUPPLY EFFICIENCY

Where:
POUT = Output power in Watts (W)
PIN = Input power in Watts (W)
Efficiency = Unitless value
Note:
Efficiency expressed as a percentage:

UNIT 2: SERIES CIRCUITS (R1, R2, , Rn)

TOTAL RESISTANCE

Where:
RT = Total series resistance in Ohms (Ω)
Rn
= Circuit’s last resistor in Ohms (Ω)

KIRCHHOFF’S VOLTAGE LAW

Where:
VS = Voltage source in Volts (V)
Vn = Circuit’s last voltage drop in Volts (V)

VOLTAGE – DIVIDER

Where:
Vx = Voltage drop in Ohms (Ω)
Rx
= Resistance where Vx occurs in Ohms (Ω)

RT = Total series resistance in Ohms (Ω)
VS
= Voltage source in Volts (V)

TOTAL POWER

Where:
PT = Total power in Watts (W)
Pn = Circuit’s last resistor’s power in Watts (W)

UNIT 3: PARALLEL CIRCUITS (R1||R2||||Rn)

TOTAL RESISTANCE

Where:
RT = Total parallel resistance in Ohms (Ω)
Rn
= Circuit’s last resistor in Ohms (Ω)

TOTAL RESISTANCE – TWO RESISTORS IN PARALLEL

Where:
RT = Total parallel resistance in Ohms (Ω)

TOTAL RESISTANCE – EQUAL-VALUE RESISTORS

Where:
RT = Total parallel resistance in Ohms (Ω)
R = Resistor Value in Ohms (Ω)
n = Number of equal value resistors (Unitless)

UNKNOWN RESISTOR

Where:
Rx = Unknown resistance in Ohms (Ω)
RA = Known parallel resistance in Ohms (Ω)
RT = Total parallel resistance in Ohms (Ω)

KIRCHHOFF’S CURRENT LAW

Where:
n = Number of currents into node (Unitless)
m = Number of currents going out of node (Unitless)

CURRENT – DIVIDER

Where:
Ix = Branch “x” current in Amperes (A)
RT = Total parallel resistance in Ohms (Ω)
Rx = Branch “x” resistance in Ohms (Ω)
IT = Total current in Amperes (A)

TWO-BRANCH CURRENT – DIVIDER

Where:
I1 = Branch “1” current in Amperes (A)
R2 = Branch “2” resistance in Ohms (Ω)
R1 = Branch “1” resistance in Ohms (Ω)
IT = Total current in Amperes (A)

TOTAL POWER

Where:
PT = Total power in Watts (W)
Pn = Circuit’s last resistor’s power in Watts (W)

OPEN BRANCH RESISTANCE

Where:
ROpen = Resistance of open branch in Ohms (Ω)
RT(Meas) = Measured resistance in Ohms (Ω)
GT(Calc) = Calculated total conductance in Siemens (S)
GT(Meas) = Measured total conductance in Siemens (S)
Note:
GT(Meas) obtained by measuring total resistance, RT(Meas)

UNIT 4: SERIES – PARALLEL CIRCUITS

BLEEDER CURRENT

Where:
IBLEEDER = Bleeder current in Amperes (A)
IT = Total current in Amperes (A)
IRL1 = Load resistor 1 current in Amperes (A)
IRL2 = Load resistor 2 current in Amperes (A)

THERMISTOR BRIDGE OUTPUT

Where:
= Change in output voltage in Volts (V)
= Change in thermal resistance in Ohms (Ω)
VS = Voltage source in Volts (V)
R = Resistance value in Ohms (Ω)

UNKNOWN RESISTANCE IN A WHEATSTONE BRIDGE

Where:
RX = Unknown resistance in Ohms (Ω)
RV = Variable resistance in Ohms (Ω)
R2 = Resistance 2 in Ohms (Ω)
R4 = Resistance 4 in Ohms (Ω)

UNIT 5: MAGNETISM AND ELECTROMAGNETISM

MAGNETIC FLUX DENSITY

Where:
B = Magnetic flux density in Tesla (T)
= Flux in Weber (Wb)
(Greek letter Phi)
A = Cross-sectional area in square meters (m2)
Note:
Tesla (T) equals a Weber per square meter (Wb/m2)

RELATIVE PERMEABILITY

Where:
= Relative permeability (Unitless)
(Greek letter Mu)
= Permeability in Webers per Ampere-turn · meter
(Wb/At·m)
= Vacuum permeability in Webers per Ampere-
turn · meter (Wb/At·m)
Note:
= Wb/ At·m

RELUCTANCE

Where:
R = Reluctance in Ampere-turn per Weber (At/Wb)
ɭ = Length of magnetic path in meters (m)
µ = Permeability in Weber per Ampere-turn · meter
(Wb/At · m)
A = Cross-sectional area in meters squares (m2)

MAGNETOMOTIVE FORCE

Where:
Fm = Magnetomotive force (mmf) in Ampere-turn (At)
N
= Number of Turns of wire (t)

I = Current in Amperes (A)

MAGNETIC FLUX

Where:
= Flux in Weber (Wb)
Fm = Magnetomotive force in Ampere-turn (At)
R = Reluctance in Ampere-turn per Weber (At/Wb)

MAGNETIC FIELD INTENSITY

Where:
H = Magnetic field intensity in Amperes-turn per
meter (At/m)
Fm = Magnetomotive force in Ampere-turn (At)
ɭ = Length of material in meters (m)

INDUCED VOLTAGE

Where:
vind = Induced voltage in Volts (V)
B = Magnetic flux density in Tesla (T)
ɭ = Length of the conductor exposed to the magnetic
field in meters (m)
v = Relative velocity in meters per second (m/s)
Note:
Tesla (T) equals a Weber per square meter (Wb/m2)

FARADAY’S LAW

Where:
vind = Induced voltage in Volts (V)
N = Number of turns of wire in the coil (Unitless)
= Rate of change of magnetic field with respect
to the coil in Webers per second (Wb/s)

ELECTRIC CIRCUITS II

UNIT 1: ALTERNATE CURRENT & INDUCTORS

ALTERNATE CURRENT

FREQUENCY & PERIOD

Where:
f = Frequency in Hertz (Hz)
T = Period in Seconds (s)
Note:
1 Hertz = 1 cycle per 1 second

PEAK TO PEAK VOLTAGE

Where:
Vpp = Peak to peak voltage in Volts (V)
Vp = Peak voltage in Volts (V)

ROOT MEAN SQUARE (RMS) VOLTAGE

Where:
Vrms = Root mean square voltage in Volts (V)
Vp = Peak voltage in Volts (V)

HALF-CYCLE AVERAGE VOLTAGE

Where:
Vavg = Half-cycle average voltage in Volts (V)
Vp = Peak voltage in Volts (V)

RADIAN & DEGREE CONVERSION

Where:
Rad = Number of radians in Rad (rad)
Degrees = Number of degrees in Degrees (0)
Note:
= 3.1416 (Greek letter Pi)

GENERATOR OUTPUT FREQUENCY

Where:
f = Frequency in Hertz (Hz)
Number of pole pairs = Number of pole pairs (Unitless)
rps = Revolutions per second in Revolutions per
Second (rps)

PEAK TO PEAK CURRENT

Where:
Ipp = Peak to peak current in Amperes (A)
Ip = Peak current in Amperes (A)

ROOT MEAN SQUARE (RMS) CURRENT

Where:
Irms = Root mean square current in Amperes (A)
Ip = Peak current in Amperes (A)

HALF-CYCLE AVERAGE CURRENT

Where:
Iavg = Half-cycle average current in Amperes (A)
Ip = Peak current in Amperes (A)

SINE WAVE GENERAL FORMULA

Where:
y = Instantaneous voltage or current value
at angle in Volts or Amperes (V or A)
(Greek letter Theta)
A = Maximum voltage or current value in Volts or
Amperes (V or A)
= Angle where given instantaneous voltage or
current value exists

SINE WAVE LAGGING THE REFERENCE

Where:
y = Instantaneous voltage or current value
at angle in Volts or Amperes (V or A)
A = Maximum voltage or current value in Volts or
Amperes (V or A)
= Angle where given instantaneous voltage or
current value exists
= Angle sine wave is shifted right (lagging) of
reference (Greek letter Phi)

ANGULAR VELOCITY

Where:
= Angular velocity in Radians per second (rad/s)
(Small Greek letter omega)
f = Frequency in Hertz (Hz)
Note:
= 3.1416

SINE WAVE VOLTAGE

Where:
v = Sinusoidal voltage in Volts (V)
Vp = Peak voltage in Volts (V)
f = Frequency in Hertz (Hz)
t = Time in Seconds (s)
Note:
= 3.1416

PULSE WAVEFORM AVERAGE VALUE

Where:
vavg = Pulse waveform average value in Volts (V)
baseline = Baseline in Volts (V)
duty cycle = Percent duty cycle in Percent/100%
(Unitless)
Amplitude = Amplitude in Volts (V)

SINE WAVE LEADING THE REFERENCE

Where:
y = Instantaneous voltage or current value
at angle in Volts or Amperes (V or A)
A = Maximum voltage or current value in Volts or
Amperes (V or A)
= Angle where given instantaneous voltage or
current value exists
= Angle sine wave is shifted left (leading) of
reference

PHASE ANGLE

Where:
= Angle sine wave is shifted in Radians (rad)
= Angular velocity in Radians per second (rad/s)
t = Time in Seconds (s)

DUTY CYCLE

Where:
Percent duty cycle = Percent duty cycle in Percentage (%)
tw = Pulse width in Seconds (s)
T = Period in Seconds (s)
F = Frequency in Hertz (Hz)

INDUCTORS

INDUCED VOLTAGE

Where:
vind = Induced voltage in Volts (V)
L = Inductance in Henries (H)
= Time rate of change of the current in Amperes
per second (A/s)

INDUCTANCE OF A COIL

Where:
L = Inductance of a coil in Henries (H)
N = Number of turns of wire (Unitless)
= Permeability in Henries per meter (H/m)
A = Cross-sectional area in Meters squared (m2)
= Core length in Meters (m)
Notes:
Permeability in H/m is equal to Wb/At·m
Non-magnetic core = Permeability of a vacuum, µ0
µ0 = 4 x 10-7 H/m

RL TIME CONSTANT

Where:
= RL time constant in Seconds (s) (Greek letter Tau)
L = Inductance in Henries (H)
R = Resistance in Ohms (Ω)

GENERAL EXPONENTIAL VOLTAGE FORMULA

Where:
v = Instantaneous voltage at time, t, in Volts (V)
VF = Voltage final value in Volts (V)
Vi = Voltage initial value in Volts (V)
R = Resistance in Ohms (Ω)
t = Time in Seconds (s)
L = Inductance in Henries (H)

INDUCTOR ENERGY STORAGE

Where:

W = Energy in Joules (J)

L = Inductance in Henries (H)
I = Current in Amperes (A)

TOTAL INDUCTANCE – SERIES

Where:
LT = Total series inductance in Henries (H)
Ln = Circuit’s last inductor in Henries (H)

TOTAL INDUCTANCE – PARALLEL

Where:
LT = Total parallel inductance in Henries (H)
Ln
= Circuit’s last inductor in Henries (H)

RL CIRCUIT CURRENT INCREASE AND DECREASE

FOR GIVEN NUMBER OF TIME CONSTANTS

# of Time Constants

Approx % of Final Current

Approx % of Initial Charge

1

63

37

2

86

14

3

95

5

4

98

2

5

99
Considered 100%

1
Considered 0%

GENERAL EXPONENTIAL CURRENT FORMULA

Where:
i = Instantaneous current at time, t, in Amperes (A)
IF = Current final value in Amperes (A)
Ii = Current initial value in Amperes (A)
R = Resistance in Ohms (Ω)
t = Time in Seconds (s)
L = Inductance in Henries (H)

INDUCTIVE REACTANCE

Where:
XL = Inductive reactance in Ohms (Ω)
f = Frequency in Hertz (Hz)
L = Inductance in Henries (H)
Note:
= 3.1416 (Greek letter “Pi”)

INDUCTOR REACTIVE POWER

Where:
Pr = Reactive Power in Watts (W)
Vrms = Voltage rms in Volts (V)
Irms = Current rms in Amperes (A)
XL = Inductive reactance in Ohms (Ω)

UNIT 2: RL CIRCUITS

SERIES RL CIRCUIT

IMPEDANCE IN RECTANGULAR FORM

Where:

Z = Impedance in Ohms (Ω)

R = Resistance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)
Note:
Bold letters represent complete phasor quantities.
For example, “
Z” in the formula above

VOLTAGE IN RECTANGULAR FORM

Where:

Vs = Voltage in Volts (V)

VR = Resistor voltage in Volts (V)
VL = Inductor voltage in Volts (V)

INDUCTOR TRUE POWER

Where:
Ptrue = True Power in Watts (W)
Irms = Current rms in Amperes (A)
RW = Winding resistance in Ohms (Ω)

COIL QUALITY FACTOR

Where:
Q = Coil quality factor (Unitless)
XL = Inductive reactance in Ohms (Ω)
RW = Winding resistance of the coil or the resistance
in series with the coil in Ohms (Ω)
Note:
Circuit Q and the coil Q are the same when the resistance is only the coil winding resistance

IMPEDANCE IN POLAR FORM

Where:

Z = Impedance in Ohms (Ω)

R = Resistance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)
Note:
= Magnitude
= Phase Angle

VOLTAGE IN POLAR FORM

Where:

Vs = Voltage in Volts (V)

VR = Resistor voltage in Volts (V)
VL = Inductor voltage in Volts (V)

LEAD CIRCUIT

ANGLE BETWEEN VOLTAGE IN & OUT

Where:
= Angle between voltage in and out in Degrees (0)
R = Resistance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)

OUTPUT VOLTAGE MAGNITUDE

Where:
Vout = Voltage output in Volts (V)
XL = Inductive reactance in Ohms (Ω)
R = Resistance in Ohms (Ω)

LAG CIRCUIT

ANGLE BETWEEN VOLTAGE IN & OUT

Where:
= Angle between voltage in and out in Degrees (0)
XL = Inductive reactance in Ohms (Ω)
R = Resistance in Ohms (Ω)

OUTPUT VOLTAGE MAGNITUDE

Where:
Vout = Output voltage in Volts (V)
R = Resistance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)
Vin = Input voltage in Volts (V)

PARALLEL RL CIRCUIT

TOTAL 2-COMPONENT IMPEDANCE

Where:

Z = Total 2-component impedance in Ohms (Ω)

R = Resistance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)

CURRENT IN POLAR FORM

Where:

Itot = Total current in Amperes (A)

IR = Resistor current in Amperes (A)
IL = Inductor current in Amperes (A)

TOTAL ADMITTANCE

Where:

Y = Total admittance in Siemens (S)

G = Conductance in Siemens (S)
BL = Inductive Susceptance in Siemens (S)
Note:

CURRENT IN RECTANGULAR FORM

Where:

Itot = Total current in Amperes (A)

IR = Resistor current in Amperes (A)
IL = Inductor current in Amperes (A)

PARALLEL TO SERIES FORM CONVERSION

Where:
Req = Resistance in Ohms (Ω)
Z = Impedance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)
= Angle where given instantaneous voltage or
current value exists

POWER

RL CIRCUIT REACTIVE POWER

Where:
Pr = Reactive power in Volt-Ampere Reactive (VAR)
Itot = Total current in Amperes (A)
XL = Inductive reactance in Ohms (Ω)

UNIT 3: CAPACITORS

CAPACITANCE

Where:
C = Capacitance in Farads (F)
Q = Charge in Coulombs (C)
V = Voltage in Volts (V)

ENERGY STORED IN A CAPACITOR

Where:

W = Energy in Joules (J)

C = Capacitance in Farads (F)
V = Voltage in Volts (V)

DIELECTRIC CONSTANT (RELATIVE PERMITTIVITY)

Where:
= Dielectric constant (Unitless)
(Greek letter Epsilon)
= Absolute permittivity of a material in Farads per
meter (F/m)
= Absolute permittivity of a vacuum in Farads per
meter (F/m)
Note:
= 8.85 x 10-12 F/m

CAPACITANCE

Where:
C = Capacitance in Farads (F)
A = Plate area in Meters squared (m2)
= Dielectric constant (Unitless)
d = Plate separation in Meters (m)
Note:
If d is in mils, 1 mil = 2.54 x 10-5 meters

SERIES CAPACITORS

TOTAL CHARGE

Where:
QT = Total charge in Coulombs (C)
Qn = Circuit’s last capacitor charge in Coulombs (C)

TOTAL CAPACITANCE

Where:
CT = Total series capacitance in Farads (F)
Cn
= Circuit’s last capacitor’s capacitance in

Farads (F)

TOTAL CAPACITANCE – TWO CAPACITORS

Where:
CT = Total series capacitance in Farads (F)

VOLTAGE ACROSS A CAPACITOR

Where:
Vx = Voltage drop in Volts (V)
CT = Total series capacitance in Farads (F)
Cx = Capacitor x’s capacitance in Farads (F)
VT = Total voltage in Volts (V)

TOTAL CAPACITANCE – EQUAL-VALUE CAPACITORS

Where:
CT = Total series capacitance in Farads (F)
n = Number of equal value capacitors (Unitless)

PARALLEL CAPACITORS

TOTAL CHARGE

Where:
QT = Total charge in Coulombs (C)
Qn = Circuit’s last capacitor charge in Coulombs (C)

TOTAL CAPACITANCE – EQUAL-VALUE CAPACITORS

Where:
CT = Total series capacitance in Farads (F)
n = Number of equal value capacitors (Unitless)

CAPACITORS IN DC CIRCUITS

RC TIME CONSTANT

Where:
= Time constant in Seconds (s)
R = Resistance in Ohms (Ω)
C = Capacitance in Farads (F)

TOTAL CAPACITANCE

Where:
CT = Total series capacitance in Farads (F)
Cn
= Circuit’s last capacitor’s capacitance in

Farads (F)

RC CIRCUIT CURRENT INCREASE AND DECREASE

FOR GIVEN NUMBER OF TIME CONSTANTS

# of Time Constants

Approx % of Final Current

Approx % of Initial Charge

1

63

37

2

86

14

3

95

5

4

98

2

5

99
Considered 100%

1
Considered 0%

GENERAL EXPONENTIAL VOLTAGE FORMULA

Where:
v = Instantaneous voltage at time, t, in Volts (V)
VF = Voltage final value in Volts (V)
Vi = Voltage initial value in Volts (V)
t = Time in Seconds (s)
= Time constant in Seconds (s)

CHARGING TIME TO A SPECIFIED VOLTAGE

Where:
t = Time in Seconds (s)
R = Resistance in Ohms (Ω)
C = Capacitance in Farads (F)
v = Specified voltage level in Volts (V)
VF = Final voltage level in Volts (V)
Note:
Assumes Vi = 0 Volts

GENERAL EXPONENTIAL CURRENT FORMULA

Where:
i = Instantaneous current at time, t, in Amperes (A)
IF = Current final value in Amperes (A)
Ii = Current initial value in Amperes (A)
t = Time in Seconds (s)
= Time constant in Seconds (s)

DISCHARGING TIME TO A SPECIFIED VOLTAGE

Where:
t = Time in Seconds (s)
R = Resistance in Ohms (Ω)
C = Capacitance in Farads (F)
v = Specified voltage level in Volts (V)
Vi = Initial voltage level in Volts (V)
Note:
Assumes VF = 0 Volts

CAPACITORS IN AC CIRCUITS

INSTANTANEOUS CAPACITOR CURRENT

Where:
i = Instantaneous current in Amperes (A)
C = Capacitance in Farads (F)
= Instantaneous rate of change of the voltage
across the capacitor in Volts per second (V/s)

CAPACITOR REACTIVE POWER

Where:
Pr = Reactive Power in Volt-Ampere Reactive (VAR)
Vrms = Voltage rms in Volts (V)
Irms = Current rms in Amperes (A)
XC = Capacitive reactance in Ohms (Ω)

CAPACITIVE REACTANCE

Where:
XC = Capacitive reactance in Ohms (Ω)
f = Frequency in Hertz (Hz)
C = Capacitance in Farads (F)
Note:
= 3.1416 (Greek letter “Pi”)

SWITCHED-CAPACITORS CIRCUITS

AVERAGE CURRENT

Where:
I1(avg) = Instantaneous current in Amperes (A)
C = Capacitance in Farads (F)
V1 = Voltage 1 in Volts (V)
V2 = Voltage 2 in Volts (V)
T = Period of time in Seconds (s)

UNIT 4: RC CIRCUITS

RC SERIES CIRCUITS

IMPEDANCE IN RECTANGULAR FORM

Where:

Z = Impedance in Ohms (Ω)

R = Resistance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)

OHM’S LAW

Where:

I = Current in Amperes (A)

Z = Impedance in Ohms (Ω)

V = Voltage in Volts (V)

VOLTAGE IN RECTANGULAR FORM

Where:

Vs = Voltage in Volts (V)

VR = Resistor voltage in Volts (V)
VC = Capacitor voltage in Volts (V)

LEAD CIRCUIT

ANGLE BETWEEN VOLTAGE IN & OUT

Where:
= Angle between voltage in and out in Degrees (0)
XC = Capacitive reactance in Ohms (Ω)
R = Resistance in Ohms (Ω)

EQUIVALENT RESISTANCE

Where:
R = Equivalent resistance in Ohms (Ω)
T = Period of time in Seconds (s)
C = Capacitance in Farads (F)
f = Frequency in Hertz (Hz)

IMPEDANCE IN POLAR FORM

Where:

Z = Impedance in Ohms (Ω)

R = Resistance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)

VOLTAGE IN POLAR FORM

Where:

Vs = Voltage in Volts (V)

VR = Resistor voltage in Volts (V)
VC = Capacitor voltage in Volts (V)

OUTPUT VOLTAGE MAGNITUDE

Where:
Vout = Voltage output in Volts (V)
R = Resistance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)

LAG CIRCUIT

ANGLE BETWEEN VOLTAGE IN & OUT

Where:

= Angle between voltage in and out in Degrees (0)
R = Resistance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)

RC PARALLEL CIRCUITS

TOTAL 2-COMPONENT IMPEDANCE

Where:

Z = Total 2-component impedance in Ohms (Ω)

R = Resistance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)

OHM’S LAW

Where:

I = Current in Amperes (A)

V = Voltage in Volts (V)

Y = Admittance in Siemens (S)

CURRENT IN RECTANGULAR FORM

Where:

Itot = Total current in Amperes (A)

IR = Resistor current in Amperes (A)
IC = Capacitor current in Amperes (A)

PARALLEL TO SERIES FORM CONVERSION

Where:
Req = Resistance in Ohms (Ω)
Z = Impedance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)
= Angle where given instantaneous voltage or
current value exists

OUTPUT VOLTAGE MAGNITUDE

Where:
Vout = Voltage output in Volts (V)
XC = Capacitive reactance in Ohms (Ω)
R = Resistance in Ohms (Ω)

TOTAL ADMITTANCE

Where:

Y = Total admittance in Siemens (S)

G = Conductance in Siemens (S)
BC = Capacitive susceptance in Siemens (S)
Note:

CURRENT IN POLAR FORM

Where:

Itot = Total current in Amperes (A)

IR = Resistor current in Amperes (A)
IC = Capacitor current in Amperes (A)

RC SERIES –PARALLEL CIRCUITS

PHASE ANGLE

Where:
Req = Resistance in Ohms (Ω)
Z = Impedance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)
= Angle where given instantaneous voltage or
current value exists

POWER

APPARENT POWER

Where:
Pa = Apparent power in Volt-ampere (VA)
I = Current in Amperes (A)
Z = Impedance in Ohms (Ω)

POWER FACTOR

Where:
PF = Power Factor (Unitless)
= Phase angle in Degrees (0)

OSCILLATOR AND FILTER

OSCILLATOR OUTPUT FREQUENCY

Where:
fr = Output frequency in Hertz (Hz)
R = Resistance in Ohms (Ω)
C = Capacitance in Farads (F)
Note:
= 3.1416

UNIT 5: RLC CIRCUITS AND PASSIVE FILTERS

RLC SERIES CIRCUITS

TOTAL REACTANCE

Where:
Xtot = Total reactance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)

TOTAL IMPEDANCE IN POLAR FORM

Where:

Z = Total impedance in Ohms (Ω)

R = Resistance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)
Xtot = Total reactance in Ohms (Ω)
Note:
When XL > XC, the angle is positive
When XC > XL, the angle is negative

TRUE POWER

Where:
Ptrue = True power in Watts (W)
V = Voltage in Volts (V)
I = Current in Amperes (A)
= Phase angle in Degrees (0)

FILTER CUTOFF FREQUENCY

Where:
fc = Cutoff frequency in Hertz (Hz)
R = Resistance in Ohms (Ω)
C = Capacitance in Farads (F)
Note:
= 3.1416

TOTAL IMPEDANCE IN RECTANGULAR FORM

Where:

Z = Total impedance in Ohms (Ω)

R = Resistance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)
XC = Capacitive reactance in Ohms (Ω)

RESONANT FREQUENCY

Where:
fr = Resonant frequency in Hertz (Hz)
L = Inductance in Henries (H)
C = Capacitance in Farads (F)
Note:
At resonance, XL = XC and the j terms cancel
= 3.1416

RLC PARALLEL CIRCUITS

TOTAL CURRENT

Where:

Itot = Total current in Amperes (A)

IR = Resistor current in Amperes (A)
IC = Capacitor current in Amperes (A)
IL = Inductor current in Amperes (A)
ICL = Total current into the L and C branches
in Amperes (A)

RLC PARALLEL RESONANCE

RESONANT FREQUENCY – IDEAL

Where:
fr = Resonant frequency in Hertz (Hz)
L = Inductance in Henries (H)
C = Capacitance in Farads (F)
Note:
At resonance, XL = XC and Zr =
= 3.1416

CURRENT AND PHASE ANGLE

Where:
Itot = Total current in Amperes (A)
VS = Voltage source in Volts (V)
Zr = Impedance at resonance in Ohms (Ω)

RESONANT FREQUENCY – PRECISE

Where:
fr = Resonant frequency in Hertz (Hz)
RW = Winding resistance in Ohms (Ω)
C = Capacitance in Farads (F)
L = Inductance in Henries (H)
Note:
= 3.1416

RLC SERIES – PARALLEL CIRCUITS

SERIES-PARALLEL TO PARALLEL CONVERSION

EQUIVALENT INDUCTANCE

Where:
Leq = Equivalent inductance in Henries (H)
L = Inductance in Henries (H)
Q = Coil quality factor (Unitless)

EQUIVALENT PARALLEL RESISTANCE

Where:
Rp(eq) = Equivalent parallel resistance in Ohms (Ω)
RW = Winding resistance in Ohms (Ω)
Q = Coil quality factor (Unitless)

NON-IDEAL TANK CIRCUIT

TOTAL IMPEDANCE AT RESONANCE

Where:
ZR = Total impedance in Ohms (Ω)
RW = Resistance in Ohms (Ω)
Q = Coil quality factor (Unitless)

SPECIAL TOPICS

RESONANT CIRCUIT BANDWIDTH

BANDWIDTH

Where:
BW = Bandwidth in Hertz (Hz)
f2 = Upper critical frequency at Z=0.707·Zmax
in Hertz (Hz)
f1 = Lower critical frequency at Z=0.707·Zmax
in Hertz (Hz)

BANDWIDTH AND QUALTIY FACTOR

Where:
BW = Bandwidth in Hertz (Hz)
fr = Center (resonant) frequency in Hertz (Hz)
Q = Coil quality factor (Unitless)

PASSIVE FILTERS

POWER RATIO IN DECIBELS

Where:
dB = Power ratio in decibels (dB)
Pout = Output power in Watts (W)
Pin = Input power in Watts (W)

OVERALL QUALITY FACTOR WITH AN EXTERNAL LOAD

Where:
QO = Overall quality factor (Unitless)
Rp(tot)= Total parallel equivalent resistance in Ohms (Ω)
XL = Inductive reactance in Ohms (Ω)

CENTER (RESONANT) FREQUENCY

Where:
fr = Center (resonant) frequency in Hertz (Hz)
f1 = Lower critical frequency at Z=0.707·Zmax
in Hertz (Hz)
f2 = Upper critical frequency at Z=0.707·Zmax
in Hertz (Hz)

VOLTAGE RATIO IN DECIBELS

Where:
dB = Power ratio in decibels (dB)
Vout = Output voltage in Volts (V)
Vin = Input voltage in Volts (V)

LOW-PASS & HIGH-PASS FILTERS

RC FILTERS

Where:
fC = Filter critical frequency in Hertz (Hz)
R = Resistance in Ohms (Ω)
C = Capacitance in Farads (F)
Note:
= 3.1416
At fC, Vout = (0.707)·Vin

SERIES RESONANT BAND-PASS FILTER

Where:
BW = Bandwidth in Hertz (Hz)
f0 = Center frequency in Hertz (Hz)
Q = Coil quality factor (Unitless)

RL FILTERS

Where:
fc = Filter critical frequency in Hertz (Hz)
L = Inductance in Henries (H)
R = Resistance in Ohms (Ω)
Note:
= 3.1416
At fC, Vout = (0.707)·Vin

GENERAL INFORMATION

AREA AND VOLUMES

AREAS

CIRCLE AREA

Where:
A = Circle area in meters squared (m2)
r = Radius in meters (m)
Note:
= 3.1416

RECTANGULAR AND POLAR FORMS

RECTANGULAR FORM

Where:
A = Coordinate value on real axis (Horizontal Plane)
j = j operator
B = Coordinate value on imaginary axis (Vertical Plan)
Note:
“j operator” prefix indicates designated coordinate value is on imaginary axis.

COMPLEX PLANE AND RECTANGULAR FORM PHASOR

+A
Quadrant 1
Quadrant 3
Quadrant 4
-A
+jB
-jB
(A + jB)
(A – jB)
(-A + jB)
(-A – jB)
Quadrant 2
00/3600
1800
900
2700

POLAR FORM

Where:
C = Phasor magnitude
= Phasor angle relative to the positive real axis

COMPLEX PLANE AND POLAR FORM PHASOR

Real Axis
Quadrant 1
Quadrant 3
Quadrant 4
+j
-j
Length = Magnitude
–
Quadrant 2
+

RECTANGULAR TO POLAR CONVERSION

Where:
A = Coordinate value on real axis (Horizontal Plane)
j = j operator
B = Coordinate value on imaginary axis (Vertical Plan)
C = Phasor magnitude
= Phasor angle relative to the positive real axis
Note:
To calculate C:

To calculate in Quadrants 1 and 4 (A is positive):

Use +B for +B values, -B for –B values

To calculate in Quadrants 2 and 3 (A is negative):

Use for +B values
Use for –B values

POLAR TO RECTANGULAR CONVERSION

Where:
C = Phasor magnitude
= Phasor angle relative to the positive real axis
A = Coordinate value on real axis (Horizontal Plane)
j = j operator
B = Coordinate value on imaginary axis (Vertical Plan)
Note:
To calculate A:

To calculate B:

Electric Circuits Lab

Inductors in DC Circuits

I.

Objectives:

After completing this lab experiment, you should be able to:

· Measure the resistance and Inductance.

· Use the Oscilloscope and Function generator.

· Measure the LR time constant using VR and VL.

· Understand the effect of series and parallel inductors on LR time constant.

II.

Parts List:

· Resistor (1) 5.1 kΩ

· Inductor (2) 100mH

III.

Procedures:

Part I:

1.
Construct the circuit shown in
Figure 1 in Multisim. (You may use either the clock voltage component or the function generator.)

PP

Figure 1: RL Circuit

2.
Connect Channel A of the oscilloscope across the resistor and Channel B across the inductor.

3.
Set the voltage source to
5VPP; 300 Hz, Square wave, 50% duty cycle

4. You should be able to see the waveform as shown below. (Use Volts/Div and Time/DIV settings to adjust the signal)

Figure 2. Voltage across the inductor and resistor

5.
Calculate the time constant of an LR circuit.
Record the result in
Table 1 below under the calculated value.

 = L/R

	Calculated value	Measured value using VL	Measured value using VR
Time constant ()	19.6 us	20.319 us	20.398 us

Table 1: Calculated and measured time constant values

6. Turn on the cursors on the oscilloscope

7.
Measuring the time constant with VL: (shown in Figure 3)

i.
Set Channel A to “0” to turn off Channel A signal.

ii.
Measure the peak value of the voltage across the resistor, by placing one of the cursors at the peak point _____5.002 V____.

iii.
Calculate the 37% of the above value ___1.85V______.

iv.
Place the second cursor at the voltage calculated above in step (iii).

v.
Observe the change in time (T2-T1) value on the scope, which is the value of one time constant.

vi.
Record the T2-T1 value in
Table 1 above under measured value using VL.

Figure 3: Measuring RL time constant using VL example (L = 150 mH)

Note: your scope screen will be different

8.
Set Channel B to “0” to turn it off.

9.
Set Channel A to “AC”

10. Adjust the Trigger settings, if needed, and you should be able to see the waveform as shown below. (Use Volts/Div and Time/DIV knobs to adjust the signal)

Figure 4: Voltage across the resistor

11.
Measuring the time constant: (shown in Figure 5)

i.

Measure the peak value of the signal, by placing one of the cursors (T1) at the peak point and the other cursor (T2) at the negative peak.
Calculate the total peak-to-peak voltage (T1-T2) _4.998V________.

ii.
Calculate the 63% of the above value __3.15V_______.

iii.
Place the second cursor (T2) at the negative peak value plus the step (ii) value above
.

iv.
Place T1 at the negative peak just before the signal begins to rise.

vii.
Observe the dT (T2-T1) value on the scope, which is one time constant.

viii.
Record the result in
Table 1 above under measured value using VR.

Figure 5: Measuring RL time constant using VR example (L = 150 mH)

Note: your scope screen will be different

Part II:

12.
Place two inductors in series as shown below.

Figure 6: Series Inductors

13.
Calculate the total inductance value and
record the results in
Table 2 (Calculated) below.

14.

Measure the total inductance value. (If you have the proper measuring device to do so). Use the following procedure to measure the inductance in Multisim if you do not have the proper measuring device.

i.
Connect the Impedance Meter (Simulate >>Instruments>>LabView Instruments>>Impedance Meter) as shown in
Figure 7.

ii.
Measure the inductive reactance, XL, as shown in
Figure 7

.

iii.
Calculate the inductance using the equation. and
record the value in
Table 2 (Measured).

Calculated Value

Measured Value

Inductance

200

199.99

Table 2: Series Inductors

Figure 7. Impedance Meter in Multisim Example

15.
Build the circuit in
Figure 8.

Figure 8: RL circuit with series Inductors

16.
Calculate the new LR time constant.
Record the result in
Table 3 below.

17.
Connect Channel A of the oscilloscope across the resistor.

18. Adjust the Trigger, if needed, and you should be able to see the waveform as shown below. (Use Volts/Div and Time/DIV knobs to adjust the signal)

Figure 9: Voltage across the resistor

19. Use the cursors on the oscilloscope to
measure the time constant (refer to step 11).
Record the result in
Table 3 below under measured value.

Calculated value

Measured value using VR

Time constant ()

40 us

41.276 us

Table 3: Calculated and measured time constant values

Part III:

20.
Place two inductors in parallel as shown below. (
Note: The 0.001 Ω resistor is
ONLY required for simulation in Multisim. Without the resistor, the mathematical model will not converge.)

Figure 10: Parallel Inductors

21.
Calculate the total inductance value and
record the results in
Table 4 (Calculated).

Calculated value

Measured value

Inductance

50

50

Table 4: Parallel Inductors

22.
Measure the total parallel inductance value. (If you have the proper device to do so). Use the following procedure to measure the inductance in Multisim if you do not have the proper measuring device.

i.
Connect the Impedance Meter (Simulate >>Instruments>>LabView Instruments>>Impedance Meter).

ii.
Measure the inductive reactance, XL
18.8496 .

iii.
Calculate the inductance using the equation and
record the value in
Table 4 (Measured).

23.
Build the following circuit. (
Note: The 0.001 Ω resistor is
ONLY required for simulation in Multisim. Without the resistor, the mathematical model will not converge.)

Figure 11: RL circuit with parallel Inductors

24.
Calculate the new LR time constant.
Record the result in
Table 5 below.

25.
Connect Channel A of the oscilloscope across the resistor.

26. You should be able to see the waveform as shown below. (Use Volts/Div and Time/DIV knobs to adjust the signal)

Figure 12: Voltage across the resistor

27. Use the cursors on the oscilloscope to
measure the time constant (refer to step 11).
Record the result in
Table 5 below under measured value.

Calculated value

Measured value using VR

Time constant ()

8.3

11.183

Table 5: Calculated and measured time constant values

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Week2 Circuit 1.ms14

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Week2 Circuit 2.ms14

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Week2 Circuit 3.ms14

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