# ELEX127 lab2 by wuzhengqin

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(ELEX 127)

OHM’S LAW AND ITS APPLICATIONS
Lab Week 2
______________________________________________________________________

OBJECTIVE

    Be familiar with DC power supply
    Measure DC voltage and current with digital multimeter (DMM)
    Verify Ohm’s law with experiment
    Verify relationship of voltage in series circuit
    Verify relationship of current in parallel circuit

BACKGROUND

a) Ohm’s Law

+
V                                    V                         I             R
I                                          -
R

VR1
b) Voltage in Series Circuit
+          R1
V                          R2        VR2
VT  VR1  VR 2  VR 3                             -
R3

VR3

c) Current in Parallel Circuit                              IT

IT  I R1  I R 2  I R 3
+
V                    I1       R1   I2   R2     I3     R3
-

Document1                                                        Electronics Department, Camosun College
Elex127 – Lab2            Ohm’s Law and Its Applications                             Page 2 of 5
_____________________________________________________________________________________

PROCEDURE

Part A. Verify Ohm’s Law
1. Obtain 3 four-band resistors (1KΩ, 2.2KΩ, 3.9KΩ, 5% tolerance) from the lab. Use
the digital multimeter (DMM) to measure them. Record the results in to Table 1.

2. Using each resistor, build the circuit as shown on the
right individually. Varying the output voltage of the            +
power supply* according to Table 1, measure the              V                   I                   R
current* thought the circuit and record measured                 -
values into Table 1.

* The instructor will demonstrate to you:
 How to connect a DC power supply to the circuit
 How to measure the current with the multimeter(DMM)

3. Compare measured values with expected (theoretical) values. Are they consistent?

Yes                    No

4. Use Excel to graph all “curves” on one chart. [Note: Review ELEX 130 assignment02
of Excel graphs if needed]

Table 1      Ampere-Volt Characteristics of Linear Resistors

R1 = ______________       R2 = ______________            R3 = ______________

I (mA)       I (mA)       I (mA)       I (mA)              I (mA)           I (mA)
Voltage
(V)       Expected     Measured      Expected    Measured             Expected        Measured

0            0                        0                                0

2

4

6

8

10

Document1                                                     Electronics Department, Camosun College
Elex127 – Lab2                 Ohm’s Law and Its Applications                                 Page 3 of 5
_____________________________________________________________________________________

Part B. Voltage in Series Circuit
5. With the resistors used in Part A, construct following series circuit. Label all resistors
with their measured values on the diagram.

VR1

+                1K
E
2K2         VR2
10V -

3K9

VR3

6. Adjust the output of DC power supply to 10 Volts and check it with DMM. [Note:
During a confliction under any circumstances, DMM will be used as the reference by defaulting]

7. Use DMM meter to measure the VOLTAGE across each resistor and record them into
Table 2.

8. Compare measured values with expected (theoretical) values. Are they consistent?

Yes                         No

Table 2          Voltage in Series Circuit

E=10V                     R1 = ___________           R2 = ___________            R3 = ___________
Expected Value                             Measured Value

VR1

VR2

VR3

VTotal                         10 V

Document1                                                              Electronics Department, Camosun College
Elex127 – Lab2                  Ohm’s Law and Its Applications                                 Page 4 of 5
_____________________________________________________________________________________

Part C. Current in Parallel Circuit
9. With the resistors used in Part A, construct following parallel circuit. Label all
resistors with their measured values on the diagram.

IT

+
E                      I1   1K      I2    2K2     I3      3K9
10V
-

10. Adjust the output of DC power supply to 10 Volts and check it with DMM. [Note:
During a confliction under any circumstances, DMM will be used as the reference by defaulting]

11. Use DMM meter to measure the CURRENT passing through each resistor as well as
the main circuit. Record them into Table 2.

12. Compare measured values with expected (theoretical) values. Are they consistent?

Yes                         No

Table 2        Current in Parallel Circuit
E=10V                     R1 = ___________           R2 = ___________             R3 = ___________
Expected Value                              Measured Value

IR1

IR2

IR3

ITotal

Document1                                                               Electronics Department, Camosun College
Elex127 – Lab2                Ohm’s Law and Its Applications                                Page 5 of 5
_____________________________________________________________________________________

13. Write down your comments on this Lab – Discussion & Conclusion.
[Hint: What have you learned from this lab? Or what does this lab try to show you? Any problem did
you have and how did you solve it?]

Document1                                                            Electronics Department, Camosun College

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