EET-117 LAB 1 F21

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Electrical Engineering

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Dec 6, 2023

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1 Centennial College ELECTRICAL ENGINEERING TECHNICIAN & TECHNOLOGY Course: EET-117 Name Student Number Date Lab #1 Metric Prefixes, Scientific Notation, and Graphing Based on Experiments in Basic Circuits by David Buchla OBJECTIVES: 1. Convert standard form numbers to scientific and engineering notation, use metric prefixes. 2. Use proper graphing techniques to plot experimental data. SUMMARY OF THEORY: Persons working in the electrical field need to be able to make concise statements about measured quantities. The basic electrical quantities encompass a very large range of numbers- from the very large to the very small. For example, the frequency of an FM radio station can be over 100 million hertz (Hz) and a capacitor can have a value of 10 billionths of a farad (F). To express very large and very small numbers, scientific (powers of 10) notation and metric prefixes are used. Metric prefixes are based on the decimal system and stand for powers of 10. They are widely used to indicate a multiple or sub-multiple of a measurement unit. Scientific notation is a means of writing any quantity as a number between 1 and 10 times a power of 10. The power of 10 is called the exponent. It simply shows how many places the decimal point must be shifted to express the number in its standard form. If the exponent is positive, the decimal point must be shifted to the right to write the number in standard form. If the exponent is negative, the decimal point must be shifted to the left. Note that 10° = 1, so multiplying by a power of 10 with an exponent of zero does not change the original number. Exponents that are a multiple of 3 are much more widely used in electrical and electronics work than exponents that are not multiples of 3. Numbers expressed with an exponent that is a multiple of 3 are said to be expressed in engineering notation. Engineering notation is particularly useful in the electrical field because of its relationship to the most widely used metric prefixes. Some examples of numbers written in standard form, scientific notation, and engineering notation are shown below (Table 1). Table 1

2 Numbers expressed in engineering notation can be simplified by using metric prefixes to indicate the appropriate power of 10. In addition, prefixes can simplify calculations. You can perform arithmetic operations on the significant figures of a problem and determine the answer's prefix from those used in the problem. For example, 4.7 kΩ + 1.5 kΩ = 6.2 kΩ. The common metric prefixes used in electricity and their abbreviations are shown in Table 2. The metric prefixes representing engineering notation are shown. Table 2 Any n u mber can be converted from one prefi x to ano th er (or no prefix) u s ing the table . Write th e num b er to be converted on the line with the decimal u n d er t h e metric prefix that appear s with the n um b er . The decimal point i s then moved directly under any other line , and the me t ric prefix immediate l y above the li n e i s used . The number can also be r ead in engineer i ng nota t ion by u s ing the power of 10 s hown immediate l y abo v e the line. Example 1: Example 2:

3 SIGNI F ICANT DIGITS: When a measurement contains approximate data, those digits known to be correct are called significant digits . Zeros that are used only for locating the decimal place are not significant, but those that are part of mea s ured quantity are significant . When reporting a measured value, the least significant uncertain digits m ay be retained, but all other uncertain digits should b e discarded. It is not correct to show either too many o r too few digits. For example, it is not valid to retain more than three digits when using a met e r that has a three-digit resolution, nor is it proper to discard valid digits, even if they are zeros. For example, if you s et a power supply to the nearest hundredth of a volt, then the recorded voltage should be reported to the h undredth place (3 . 00 V is correct, but 3 V is incorrect). For laboratory work in this course, you should normally be able to measure and retain three significant digits. To find the number of significant digits in a given number, ignore the decimal point and count the number of digits from left to right , st a rting with the first nonzero digit and ending with the last digit to the right. A ll digits counted are significant except zeros at the right end of the number . A zero on the right end of a n umber is significant only if it is to the right of the decimal point; otherwise, it is uncertain. For example, 43 . 00 contains four significant digits. The whole number 4300 may contain two, three, or four significant digits . In the absence of other information, the significance of the right-hand zeros is uncertain, and t hese digit s cannot be assumed to be significant . To avoid confusion, numbers such as these should be reported using scientific notation. For e x ample , the number 2.60 X 10 3 contains three significant figures and t he number 2 . 600 X 10 3 contains four significant figures. Rules for determining if a reported digit is significant are as follows: 1. Nonzero digits are always considered to be significant . 2. Zeros to the left of the first nonzero digit are never significant . 3. Zeros between nonzero digits are always significant . 4. When digits are shown to the right of the decimal point, zeros to the right of the digits are significant . 5. Zeros at the right end of a whole number are uncertain. Whole numbers should be reported in scientific or engineering notation to clarify the significant figures. The rule for multiplication and division: The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer. Example: A= LxW = (3.2 m)(2.8 m) = 8.96 m 2 ={original values had 2 sig. digits}=> 9.0 m 2 Videos: 1. Significant digits https://www.khanacademy.org/math/arithmetic-home/arith-review-decimals/arithmetic- significant-figures-tutorial/v/significant-figures 2. Multiplying and dividing with significant digits https://www.khanacademy.org/math/arithmetic-home/arith-review-decimals/arithmetic- significant-figures-tutorial/v/multiplying-and-dividing-with-significant-figures

4 G RAPHS: A gr aph is a visual tool that can quickly convey to the reader the relationship between variables. The eye can discern trends in magnitude or slope more easily on a graph than from tabular data . Graphs are widely used i n experimental work to present information because they enable the reader to discern variations in magnitude, slope, and direction between two quantities. In experimental work, you will graph data on many occasions. The following steps will guide you in preparing a graph : 3. Determine the type of scale that will be used. A linear scale is the most frequently used and will be discussed here. Choose a scale factor that enables all of the data to be plotted on the graph without being cramped. The most common scales are multiples of 1, 2 , 5, or 10 units per division . 4. Number the major divisions along each axis. Do not number each small division as it will make the graph appear cluttered. Each division must have equal weight . 5. Label each axis to indicate the quantity being measured and the measurement units. Usually, the measurement units are given in parentheses. 6. Plot the data points with a small dot with a small circle around each point . If additional sets of data are plotted, use other distinctive symbols (such as triangles) to identify each set . 7. Draw a smooth line that represents the data trend. It is normal practice to consider data points but to ignore minor variations due to experimental errors . 8. Title the graph , indicating with the title what the graph represents. The completed graph should be self-explanatory. Figure 1 shows an example of a set of data taken in an experiment where frequency is measured as a function of capacitance. The data is plotted in accordance to the rules given previously. Notice that not every data point lies on the smooth curve drawn to represent the "best - fit" of the data . Also, the scale factors are selected to fit all of the data points onto the graph, and the labels are given to both axes with proper measurement units. Fig. 1

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