Unit 1. ET Unit 1. Quantities, Units, and Electrical Safety. Electronics Fundamentals Circuits, Devices and Applications - Floyd

Transcription

1 ET Unit 1 Quantities, Units, and Electrical Safety

2 Scientific and Engineering Notation Very large and very small numbers are represented with scientific and engineering notation. 47,000,000 = 4.7 x 10 7 (Scientific Notation) = 47 x 10 6 (Engineering Notation)

3 Scientific and Engineering Notation = 2.7 x 10-5 (Scientific Notation) = 27 x 10-6 (Engineering Notation) = 6.05 x 10-1 (Scientific Notation) = 605 x 10-3 (Engineering Notation)

4 Metric Conversions Numbers in scientific notation can be entered in a scientific calculator using the EE key. Most scientific calculators can be placed in a mode that will automatically convert any decimal number entered into scientific notation or engineering notation.

5 SI Fundamental Units Quantity Unit Symbol length mass time electric current temperature luminous intensity amount of substance meter kilogram second ampere Kelvin candela mole m kg s A K cd mol

6 Some Important Electrical Units Except for current, all electrical and magnetic units are derived from the fundamental units. Current is a fundamental unit. Quantity Unit Symbol current charge voltage resistance power ampere coulomb volt ohm watt A C V W W

7 Engineering Metric Prefixes P peta Can you name the prefixes and their meaning? T G M k tera giga mega kilo

8 Engineering Metric Prefixes m milli 10-3 Can you name the prefixes and their meaning? m n p f micro nano pico femto

9 Metric Conversions When converting from a larger unit to a smaller unit, move the decimal point to the right. Remember, a smaller unit means the number must be larger. Smaller unit 0.47 MW = 470 kw Larger number

10 Metric Conversions When converting from a smaller unit to a larger unit, move the decimal point to the left. Remember, a larger unit means the number must be smaller. Larger unit 10,000 pf = 0.01 mf Smaller number

11 Metric Arithmetic When adding or subtracting numbers with a metric prefix, convert them to the same prefix first. 10,000 W + 22 kw = 10,000 W + 22,000 W = 32,000 W Alternatively, 10 kw + 22 kw = 32 kw

12 Metric Arithmetic When adding or subtracting numbers with a metric prefix, convert them to the same prefix first. 200 ma ma = 200 ma + 1,000 ma = 1,200 ma Alternatively, ma ma = 1.2 ma

13 Error, Accuracy, and Precision Experimental uncertainty is part of all measurements. Error is the difference between the true or best accepted value and the measured value. Accuracy is an indication of the range of error in a measurement. Precision is a measure of repeatability. } Error Precise, but not accurate.

14 Significant Digits When reporting a measured value, one uncertain digit may be retained but other uncertain digits should be discarded. Normally this is the same number of digits as in the original measurement. Assume two measured quantities are and If the larger is divided by the smaller, the answer is 2.69 because the answer has the same uncertainty as the original measurement.

15 Significant Digits Rules for determining if a reported digit is significant are: 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. Zeros to the right of the decimal point for a decimal number are significant. 5. Zeros to the left of the decimal point with a whole number may or may not be significant depending on the measurement.

16 Rounding numbers Rounding is the process of discarding meaningless digits. Rules for rounding are: 1. If the digit dropped is greater than 5, increase the last retained digit by If the digit dropped is less than 5, do not change the last retained digit. 3. If the digit dropped is 5, increase the last retained digit if it makes it even, otherwise do not. This is called the "round-to-even" rule.

17 Electrical Safety Safety is always a concern with electrical circuits. Knowing the rules and maintaining a safe environment is everyone s job. A few important safety suggestions are: 1. Do not work alone, or when you are drowsy. 2. Do not wear conductive jewelry. 3. Know the potential hazards of the equipment you are working on; check equipment and power cords frequently. 4. Avoid all contact with energized circuits; even low voltage circuits. 5. Maintain a clean workspace. 6. Know the location of power shutoff and fire extinguishers. 7. Don t have food or drinks in the laboratory or work area.

18 Engineering notation Exponent Metric prefix Power of ten Key Terms A system for representing any number as a one-, two-, or three-digit number times a power of ten with an exponent that is a multiple of three. The number to which a base is raised. A symbol that is used to replace the power of ten in numbers expressed in scientific or engineering notation. A numerical representation consisting of a base of 10 and an exponent; the number 10 raised to a power.

19 Scientific notation Accuracy Precision Significant digit Key Terms A system for representing any number as a number between 1 and 10 times a power of ten. An indication of the range of error in a measurement. A measure of the repeatability (consistency) of a series of measurements. A digit known to be correct in a number.

20 Breadboard Setup Power Connections: Red is + voltage Black is voltage (GRD) Connect all + voltages Connect all voltages Note: leave about ¾ inch make wires short & do not strip too much from the wires