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Verification of Ohm's Law - Lab I | EEGR 203, Lab Reports of Electrical and Electronics Engineering

Material Type: Lab; Class: Intro to Electrical Lab; Subject: Electrical Engineering; University: Morgan State University; Term: Unknown 1989;

Typology: Lab Reports

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MORGAN STATE UNIVERSITY
DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
EEGR 203.002: INTRODUCTION TO ELECTRICAL LABORATORY
Instructor: Dr. Gregory M. Wilkins
Lab 1: Verification of Ohm’s Law
Prior to arriving in lab for Assignment #1, each student is responsible for purchasing a toolbox for
EEGR203. The box contains most of the things you will need for this class such as breadboard, resistors,
op-amp, etc. If you don’t know where to get one, ask your classmates or your instructor for his assistant.
You will see this reminder in all of your labs.
Please take notes and commit all you learn in each lab to memory
You will need every bit of these information to complete your project !!!
Introduction
This lab provides an introduction to the test equipment that is used throughout the EEGR203 and
other EEGR courses that you will encounter as you pursue your career. In the first exercise, the
resistance of a resistor will be calculated using the color-codes and after which we will then use a digital
multimeter (DMM) to measured the value of the same resistor. Next, a DMM is used to measure dc
voltage of the bench power supply and the dc current that is drawn from the power supply when it is
loaded with a simple resistive network. For the second exercise, AC (ALTERNATING CURRENT)
voltages are generated with a function generator and are measured using a DMM and a digital
oscilloscope. Unlike the DMM, which computes a time-average voltage or current, a digital oscilloscope
displays graphs of voltage or current versus time on a liquid crystal display (LCD). The waves generated
by the function generator through the oscilloscope used to explore important features of the oscilloscope
including time base, voltage base, triggering, and
ac / dc coupling.
Resistor color code and its uses
A color code is used to identify the resistance and tolerance of resistors without having to measure
them using a digital multi-meter or ohmmeter. Resistors that have tolerances of 5% or greater have four
color bands, whereas resistors with tolerances of 1% or less have five color bands. The color code and
method to compute the resistance and tolerance are given below and on attached sheet.
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MORGAN STATE UNIVERSITY

DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING

EEGR 203.002: INTRODUCTION TO ELECTRICAL LABORATORY

Instructor: Dr. Gregory M. Wilkins

Lab 1: Verification of Ohm’s Law

Prior to arriving in lab for Assignment #1, each student is responsible for purchasing a toolbox for EEGR203. The box contains most of the things you will need for this class such as breadboard, resistors, op-amp, etc. If you don’t know where to get one, ask your classmates or your instructor for his assistant.

You will see this reminder in all of your labs.

Please take notes and commit all you learn in each lab to memory

You will need every bit of these information to complete your project !!!

Introduction

This lab provides an introduction to the test equipment that is used throughout the EEGR203 and other EEGR courses that you will encounter as you pursue your career. In the first exercise, the resistance of a resistor will be calculated using the color-codes and after which we will then use a digital multimeter (DMM) to measured the value of the same resistor. Next, a DMM is used to measure dc voltage of the bench power supply and the dc current that is drawn from the power supply when it is loaded with a simple resistive network. For the second exercise, AC (ALTERNATING CURRENT) voltages are generated with a function generator and are measured using a DMM and a digital oscilloscope. Unlike the DMM, which computes a time-average voltage or current, a digital oscilloscope displays graphs of voltage or current versus time on a liquid crystal display (LCD). The waves generated by the function generator through the oscilloscope used to explore important features of the oscilloscope including time base, voltage base, triggering, and ac / dc coupling.

Resistor color code and its uses

A color code is used to identify the resistance and tolerance of resistors without having to measure them using a digital multi-meter or ohmmeter. Resistors that have tolerances of 5% or greater have four color bands, whereas resistors with tolerances of 1% or less have five color bands. The color code and method to compute the resistance and tolerance are given below and on attached sheet.

Resistor Color Codes

Black = 0 Green = 5

Brown = 1 Blue = 6

Red = 2 Violet = 7

Orange = 3 Gray = 8

Yellow = 4 White = 9

Tolerance Color Codes

No Band = 20% Silver = 10 % Gold = 5% Red=2%

Expressions to Determine Resistance and Tolerance

≥ 5% R = AB x 10C, tolerance = D ≤ 1% R = ABC x 10D, tolerance = E

For example, a 2 kΩ resistor with a tolerance of 5% has a color code of Red, Black, Red, Gold. Using the expression for a resistor with a tolerance ≥ 5% (four color bands) gives:

Resistance value = (red black) x10red^ or 20 x 10^2 = 2000 Tolerance = gold Therefore 5% tolerance. 5% of 2000 = 100

Therefore, this 2kΩ resistor can have a value between 1100Ω and 1900Ω.

Part 1:

  1. Push the power button to turn on the multi-meter.
  2. To use the DMM as an ohmmeter, depress the Ohm button and ensure that you have one of the lead plugged into in-let with the (Ω) symbol.
  3. Choose three resistors from your toolbox (they must not be of the same color code as the one used in the sample problem and the resistors should have different color codes). From the color code, determine the resistance and the tolerance of each resistor. Calculate the range of resistance values for each resistor based on the tolerance of the resistors.
  4. Using the DMM, measure the resistance of each resistor. To do this, insert a red banana-to-clip connector into the HI-plug and a black banana-to-clip connector into the COM-plug. Place the resistor-under-test between the red and the black connectors.

Choose five resistor R1 = 560 Ω, R2 = 330 Ω, R3 = 820 Ω, R4 = 1 kΩ and R5 = 4.7 kΩ and put them

together as shown in the circuit in Figure 2. Connect the voltage supply as shown with Vs = 8 V. Measure voltages V1, V2, V3 and the current through each of the resistors. Be sure to write down the values of each of the resistors, both the value indicated by the color bands and the values you measure using the DMM. Ask for help if you need it.

Figure 2

a. Record the value of V1, V2, and V3 that you deduced using Ohms law in the Table 1. b. Record the value of V1, V2, and V3 that you measured using the DMM c. Repeat parts a and b for the currents and also record the values in Table 2.

Do the calculated and measured values agree? Comment on why you think the values matched or why they did not if that is the case with your result.

Table 1

Measured Voltage Deduced Voltage Difference V1= V1= V2= V2= V3= V3=

Table 2

Measured Current Deduced Current Difference I 1= I 1= I 2= I 2= I 3= I 3=

Assignment

  1. From what you did what do you think is the purpose of this lab.
  2. Do all the write-up as directed in the lab. 3. Write a single paragraph that summarizes all you learned from this lab.