Question

Notes for lab dc02-Resistors and the Color Code will skip are Part 2 e, g: Part 4; Exercises 2, 4,5,6 and 3. It is important to answer the exercises correctly in each labl you should include the appropriate prefix for the unit in the Numerical Value We will not be Volt using the Volt-Ohm meter (VOM) for this lab, so skip the parts that ask for VOM measurements. The parts we You do need to complete Exercises1 Note that in Exercise 1, column (Q, kn, M0, etc.) Every measured or calculated value requires a unit!!! The base unit for resistance is Ohms (Ω). The amount of resistance is notrelated to the physical size of the resistor. The size of the resistor will depend on how much power, measured in watts (W), it can dissipate. For the remainder of we will be using %-w and y-w resistors. Larger wattage resistors have legs that can damage the protoboard, so please don't force resistors greater than into the board. the labs resistors we are using will have 4 color bands, Each color represents a digit 0-9. The first 3 bands determine the nominal resistance value. Numerical Value Color Black Brown The first two bands correspond to an integer between 10 and 99. The 3"d band corresponds to the power of 10 Red Orange that the integer is multiplied by Yellow If the first three bands were brown, red, red Green The resistance would be 12x 10' which equals 1200 Ω Blue Usually this would be written as 1.2 kΩ Purple (Violet) Grey White If the resistance is less than 10 Ω, the 3rd band will be silver (0.01) or gold (0.1) The 4th band corresponds to the tolerance: silver is +/-10% and gold is +/-5%, if there is no 4th band then the tolerance is +/-20%. Insert resistors in the protoboard when measuring- do not hold the resistors in your hands. Using the Digital MultiMeter (DMM) to measure resistance The dial needs to be turned to the top section to measure resistance ( between 11a t gives the most accuracy and precision. This will be the first setting greater than the nce. If the meter is reading 1, then the setting is too low for the resistance that is being Use the setting that actual resista at least 3 significant figures. measured. Most of the time you should be able to measure to In the figure to the left, the dial is set to 2k, which means it can be used to measure any resistance less than 2000 Ω. However, if the actual resistance is less than 200 Q the dial should be moved to that setting. The red lead is inserted in the V Ω Hz socket which can be used when measuring either voltage, resistance, or frequency The black lead is inserted in the COM socket which is the ground. It should always remain there. CE In order to take a measurement the ends of the leads are put in contact with the legs of the resistor. The meter will send a small current through the resistor and display the resistance value. It is important to maintain good contact with the resistor while the readout stabilizes. A good way of doing this is to gently push the lead down into the same holes as the resistor (see next paragraph) or to hold it firmly against the legs The figure to the left shows the protoboard that we will be using for the labs. The legs of the resistors should be inserted into holes in the protoboard. Note that in the center section, the holes are arranged in groups of 5. Each group of 5 holes are connected behind the board (and some of the vertical groups are connected together). It is important that the legs of the resistors are not placed in holes that are connected to each other for this lab. EQUIPMENT ISSUED TABLE 2.0 Laboratory Serial No. Manufacturer and Model No. Item VOM DMM DESCRIPTION OF EQUIPMENT Both the VOM and the DMM will be used in this experiment vided resistors. The VOM employs an analog scale to read resistance, voltage, and current whereas the DMM has a digital display. An analog scale is a continuous scale, requiring that the user be able to interpret the location of the pointer using the scale divisions provided. For resis- tance measurements, the analog scale is also nonlinear, resulting in smaller distances between in creasing values of resistance. Note on the VOM scale the relatively large distance between 1 and 10 Ω and the smaller distance between 100 Ω and 100 n. The digital display provides a nu- merical value with the accuracy determined by the chosen scale. For many years the analog me- ter was the instrument employed throughout the industry. In recent years, the digital meter has grown in popularity, making it important that the graduate of any technical program be adept at using both types of meters. to measure the resistance of the pro- RESUMÉ OF THEORY In this experiment, the resistance of a series of 1/2-W film resistors first will be determined from the color code and then compared with the measured value using both the VOM and the DMM. The two meters were applied to ensure familiarity with reading both an analog and a digital scale. The procedure for determining the resistance of a color-coded resistor is described in Appendix I with a listing of the numerical value associated with each color. The numerical value as- sociated with each color has been repeated in Fig. 2.1. The first two bands (those closest to the end of the resistor) determine the first two digits of the resistor value, while the third band determines the power of the power-of-10 multiplier (actually the number of zeros to follow the first two digits). If the third band is silver (0.01) or gold (0.1), it is a multiplying factor used to establish resistor val- ues less than 10 Ω. The fourth band is the percent tolerance for the chosen resistor (see Fg. 2.1). Black Browa Red Orane Yellow Green Blue Purple Gray Whie Red Red Br Silver 221 10% FIG. 2.1 22Ω-19S Ω to 242 Ω 10%.220 Ω 220 Ω RESISTORS AND THE COLOR CODE 23 For increasing wattage ratings, the size of the film resistor will increase to provide the body" required to dissipate the resulting heating effects. Resistance is never measured by an ohmmeter in a live network, due to the possibility of damaging the meter with excessively high currents and obtaining readings that have no meaning It is usually best to remove the resistor from the circuit before measuring its resistance to ensure that the measured value does not include the effect of other resistors in the system. However, if this maneuver is undesirable or impossible, make sure that one end of the resistor is not connected to any other element. The use of the VOM and DMM will be described early in the laboratory session. For the VOM, always reset the zero-adjust whenever you change scales. In addition, always choose the dial setting (RX I,RX 10, and so on) that will place the pointer in the region of the scale that will give the best reading. Finally, do not forget to multiply the reading by the proper multiplying fac- tor. For the DMM, remember that any scale marked "kl" will be reading in kilohms, and any "MI2" scale in megohms. For instance, a 91-2 resistor may read 90.7 2 on a 200-11 scale, 0.091 on a 2-kn scale, and 0.00 on a 2-Mn scale. There is no zero-adjust on a DMM meter, but make sure that R-0 when the leads are touching, or else an adjustment internal to the meter may have to be made. Any resistance above the maximum for a chosen scale will result in an O.L. indication. It is important to remember that there is no polarity to resistance measurements Either lead of the meter can be placed on either end of the resistor the resistance will be the same. Polarities will become important, however, when we measure voltages and currents in the experiments to follow. PROCEDURE The purpose of this experiment is to acquaint you with the laboratory equipment, so do not rush Learn how to read the meter scales accurately, and take your data carefully. If you are uncertain about anything, do not hesitate to ask your instructor. Part 1 Body Size (a) In the space below, draw the physical sizes of 1/4-W, 1/2-W, 1-W, and 2-W. 1-Mn film resistors (color bands brown, black, green). Note in particular that the resistance of each is the same but that the size increases with wattage rating. Identify each by its wattage rating. (b) How much larger (physically) is the 1-W resistor than the 1/2-W resistor? Is the ratio about the same for the 2-W resistor as compared with the 1-W resistor? Answer the ques- tions in sentence form. 24 EXPERIMENT dc 2 Part 2 Color Code (a) Using the procedure described in the Résumé of Theory, determine the color bands for each resistor appearing in Table 2.1. Then find each resistor in your provided kit and enter the colors for all four bands in Table 2.1, as shown by the example. (b) Enter the numerical value of each color in the next column, as shown by the example. TABLE 2.1 Resistor Nominal Value) Color Bands-Celer Color Bands-Nuerical Value Red Red Black Gold 5% 220 Ω Red Bow 10 kn 470 kΩ I Mn (e) The percent tolerance is used to determine the range of resistance levels within which the manufacturer guarantees the resistor willfall. Itits determined by first taking the percent tolerance and multiplying by the nominal resistance level. For the example in Table 2.1, the resulting resistance level urer guarantees (5%)(22 Ω)-(0.05)(22 Ω)-1-a is added to and subtracted from the nominal value to determine the range as follows: Maximum value-2261 + 1.1 Ω 23.1 Ω Minimum value-22 Ω-1.1 Ω-20.9 as shown in Table 2.2 Complete Table 2.2 for each resistor in Table 2.1. (d) Read the resistance level using the DMM and insert the value in Table 2.3. For each resistor, take the time to choose the scale that will result in the highest degree of accuracy for the measurement. Ask for assistance if you need it. Then determine the magnitude of the difference between the nominal and measured values using the following equation. The vertical bars of the equation specify that the sign resulting from the operation is not to be included in the solution. RESISTORS AND THE COLOR CODE 25 TABLE 22 Maximum Resistance Minimunm Resistance 22 n 20.9 ถ 15-5S 2 91Ω 220 n 4469 0.S 41 okn 470 kn 6,4 6.8 Ω 100% % Difference-Nominal-Measured TABLE 2.3 VoM DMM Meter Falls within Falls within Specified Resister Measured Tolerance (Ye No) Specified Differenoe 45% 23 0 Yes Yes 22.9 Ω 91Ω 220 ถ 33k3.25 470 kn ·016 6.8 Ω (e) Repeat part (d) using the VOM and insert the data in Table 2.3.As with the DMM. be sure to ask for assistance if you need it. It is very important to become familiar with the oper- ation of each meter boy10148, Dcoz.gad 1//7443 AM Page 26 EXPERIMENT dc 2 26 (r) For the DMM measarements, are all the resistors within the specified tolerance range? You can check by referencing Table 2.2 or comparing the percent tolerance to in Table 2.1. If not, how many resistors did not fall within the tolerance range (R) For the VOM measurements, are all the resistors within the specified tolerance range? Again, you can check using the range of Table 2.2 or the percent tolerance of Table 2.1. If not, how many resistors did not fall within the tolerance range? Part 3 Body Resistance Guess the resistance of your body between your hands and record the value in Table 24. Measure the resistance with the DMM by firmly holding one lead in each hand (wet your fingers and hold the leads as tight as possible), and record in the same table. If 10 mA are "lethal," what voltage (V- IR) would be required to produce the current through your body? Again, record in Table 2.4. TABLE 2.4 Guessed body resistance Measured body resistance Lethal voltage Part 4 Meter Resistance (a) Voltmeters Ideally, the internal resistance of the DMM and VOM should be infinite (like an open circuit) when voltages in a network are being measured to ensare that the meter does not alter the normal behavior of the network For the VOM, there is an ohm/volt (/V) rating written on the bottom of the scale that permits determination of the internal resistance of each scale of the meter when used as a voltmeter. For the 260 Simpson VOM, the ohm/volt rating is 20,000 ณV. The internal resistance of each setting then can be calculated by multiplying the maximum voltage reading of a scale by the ohm/volt rating. For instance, the 10-V scale will have (10 VX20,000 V) 200 kn.

Answer 1

PART 1

a) The resistors can be drawn in the increasing order of the size like 1/4 resistor will be smallest one, resistor 1/2 will be double of the first, resistor 1W will be double of 1/2W and similarly all can be drawn and this is because of the fact that the size of the resistor is directly proportional to the power rating.

b) 1W resistor will be double the size of 1/2W resistor as the size of the resistor is directly proportional to the power rating of the resistor. Yes, the ratio of the size will be the same for the resistors 2W and 1W as in the case of 1W and 1/2W.

PART 2

Date Monenical a lu Resieb olos Barde-Colo 2 Red Red Block fo on Red Red Boun gold 22 m Bortum Black germ elu 2(d) ahe 2.2 20.9a S6.451 220 231 3.3 ka okn 70kn 3.465 n 446 Sk |ma os 7.19 Pm