M3L7_GroupC11

pdf

School

Kent State University *

*We aren’t endorsed by this school

Course

13021

Subject

Electrical Engineering

Date

Apr 3, 2024

Type

pdf

Pages

Uploaded by cuttingtatum

} | | 1 | | | | i | | l | l f r M ) ~ - pr A ‘\; - N | m p i n Name_ (UM A HTING Date ! 0| LL Partners {)\k}‘“ N, 70N \ LaB 7: KIRCHHOFF's cIRculT RULES The Energizer© keeps on going, and going, and . . . . —Eveready Battery Company, Inc. OBJECTIVES e To learn how multimeters are designed so that they don’t modify the currents and voltages being measured. e To learn to measure resistance with a multimeter. ¢ To develop a method for calculating the equivalent resistance of resistors con- nected in series. e To develop a method for calculating the equivalent resistance of resistors con- nected in parallel. e To understand Kirchhoff’s circuit rules and use them to determine the cur- rents that flow in various parts of DC circuits. OVERVIEW In the last few labs, you have examined simple circuits with bulbs or resistors connected in series and parallel. The emphasis has been on learning about the concepts of current, voltage, and resistance in fairly simple DC circuits. In this lab you will look at circuits more quantitatively. Up until now you have been using computer-based sensors to measure currents and voltages. A mul- timeter is a device with the capability of measuring current and voltage. Some multimeters can also be used to measure resistance. In Investigation 1, you will learn how to use a multimeter to measure current, voltage, and resistance. LAB 7: KIRCHHOFF'S CIRCUIT RULES 129

130 In Investigation 2, you will look at circuits with resistors connected in both series and parallel and discover the rules for finding the equivalent values of net- works of resistors wired in series and parallel. Sometimes circuit elements are connected with multiple b complicated ways than simply in series or parallel. The rules for series and par- allel addition of resistances are not adequate to determine the currents flowing in such circuits. In Investigation 3 of this lab, you will learn about Kirchhoff’s circuit rules that are generally applicable to all types of circuits. atteries in more INVESTIGATION 1: MEASURING CURRENT, VOLTAGE, AND RESISTANCE Resistance, voltage, and current are fundamental electrical quantities that char- acterize all electric circuits. The multimeters available to you can be used to measure these quantities. All you need to do is choose the correct dial setting, connect the wire leads to the correct terminals on the meter, and connect the meter correctly in the circuit. Figure 7-1 shows a simplified diagram of a multimeter. (e ) Scales: 3 ~ L! K=10% 'l m=1073 M = 10° Direct current volts — DCV__ACV DCV : — Dial for selection of measurement type and scale Ohms —Q R DCA +— Direct current amps VQ CO MA 10A (o) o] & @j— Receptacles for input leads (a) (b) Figure 7-1: (a) Multimeter with voltage, current, and resistan"ce modes, and (b) symbols that will be used to represent a multimeter when it is used as an ammeter, voltmeter, or ohmmeter, respectively. A current sensor and a multimeter used to measure current are both connected in a circuit in the same way. Likewise, a voltage sensor and a multimeter used to measure voltage are both connected in a circuit in the same way. The next two activities will remind you how to connect them. The activities will also show you that when meters are connected correctly, they don’t change the currents or volt- ages being measured. You will need: ¢ digital multimeter o 2 very fresh, akaline 1.5-V D cell batteries with holders e 6 alligator clip leads e 2 #14 bulbs and sockets REALTIME PHYSICS: ELECTRICITY AND MAGNETISM e

Activity 1-1: Measuring Current with a Multimeter ~ Figure 7-2 shows two possible ways that you might connect a multimeter to mea- sure the current flowing through bulb 1. Prediction 1-1: Which of the diagrams in Figure 7-2, (b) or (c), shows the cor- rect way to connect a multimeter to measure the current through bulb 1? Explain why it should be connected this way. [Hint: In which case is the current flowing through the multimeter the same as that flowing through bulb 17] d \O\O ;( O \filn\ C 1 @ O ’@‘ 1 z ©: ©: d (a) (b) (e Figure 7-2: (a) A circuit with two light bulbs and a battery, and two possible but not necessar- ily desirable ways to connect a multimeter to measure current: (b) in series with bulb 1, and () in parallel with bulb 1. 1. Set up the basic circuit in Figure 7-2a. Use two batteries in series to make a 3-V battery. Observe the brightness of the bulbs. 2. Set the multimeter to measure current and connect it as shown in Figure 7-2b. Was the brightness of the bulbs significantly affected? [\() 3. Now connect the meter as in Figure 7-2c. Was the brightness of the bulbs sig- nificantly affected? %65 b\)lp A do@sn{ ltgh‘\’ ve Question 1-1: If the multimeter is connected correctly to measure current, it should measure the current flowing through bulb 1 without significantly affect- ing the current flowing through the bulb. Which circuit in Figure 7-2 shows the correct way to connect a multimeter? Explain based on your observations. Why is it connected in this way? B, becaue the Dulps weront afected Question 1-2: Does the multimeter appear to behave as if it is a large resistor or a small resistor? Explain based on your observations. Why is it designed in this way? small resistor pecavse wnen vsed Correct K AoRs NOr okect ‘he Coneny wirhin The CI( | Activity 1-2: Measuring Voltage with a Multimeter Figure 7-3 shows two possible ways that you might connect a multimeter to mea- sure the potential difference across bulb 1. 131 LAB 7: KIRCHHOFF'S CIRCUIT RULES

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

132 Prediction 1-2: Which of the diagrams in Figure 7-3 shows the correct way to connect a multimeter to measure the voltage across bulb 1? Explain why it should be connected this way. ) (a) (b) Figure 7-3: Two possible but not necessarily desirable ways to connect a multimeter to measure voltage: (a) in series with bulb 1, and (b) in parallel with bulb 1. 1. Set the meter to measure voltage and connect it as in Figure 7-3a. Was the brightness of the bulbs significantly affected? ho 2. Now connect the meter as in Figure 7-3b. Was the brightness significantly affected? nD Question 1-3: If the multimeter is connected correctly, it should measure the volt- age across bulb 1 without significantly affecting the current flowing through the bulb. Which circuit in Figure 7-3 shows the correct way to connect the multimeter? Explain based on your observations. Why is it connected in this way? [Hint: In which case is the voltage across the multimeter the same as that across bulb 1?] SO 1 can CO(TCC‘\'\L& measvre, the voviage Question 1-4: Does the multimeter behave as if it is a large resistor or a small resistor? Explain based on your observations. Why is it designed in this way? SHAl (eSiSrar e COVSe |+ dloesn Offect the curreny /voage hivigin clcour You just observed that even multimeters have some resistance. Now you will investigate how to measure resistance with a multimeter. In earlier labs, you observed that the resistance of a light bulb increases when the current through it causes the temperature of the filament to rise. To make the behavior of circuits more consistent, it is desirable to have circuit elements with resistances that do not change. For that reason, circuit elements known as resis- tors have been invented. The resistance of a well-designed resistor doesn’t vary with the amount of current passing through it (or with temperature), and resis- tors are inexpensive to manufacture. The most common resistors contain a form of carbon known as ).’,I'.\}‘]\il\‘ Sus- pended in a hard glue binder. It is usually surrounded by a plastic case with a color code painted on it Figure 7-4 depicts a carbon resistor cut down the middle REALTIME PHYSICS: ELECTRICITY AND MAGNETISM

Cross section of graphite material. Figure 7-4: A cutaway view of a carbon resistor. Figure 7-5 shows a carbon resistor with colored bands that tell you the value of the resistance and the tolerance (guaranteed accuracy) of this value. Figure 7-5: A carbon resistor with color bands. The first two stripes indicate the two digits of the resistance value. The third stripe indicates the power of ten multiplier, and the fourth stripe signifies the resistor’s tolerance. The key in Table 7-1 shows the corresponding values. Table 7-1: The resistor code Bands A, B, C violet = 7 black = 0 gray = 8 brown = 1 white = 9 red = 2 orange = 3 Band D yellow = 4 none = =20% green = 5 silver = *£10% blue = 6 gold = *5% As an example, look at the resistor in Figure 7-6. Its two digits are 1 and 2 and the multiplier is 10%, so its value is 12 X 102, or 12,000 ). The tolerance is +20%, so the value might actually be as large as 14,400 Q or as small as 9600 (1. Brown Orange Figure 7-6: An example of a color-coded carbon resistor. The resistance of this resistor is 12 %X 10% 0 = 20%. The appropriate way to connect -the multimeter to measure resistance is shown in Figure 7-7. When the multimeter is in its ohmmeter mode, it connects a known voltage across the resistor and measures the current through the resistor. Then resistance is calculated by the meter from R V/I. LAB 7: KIRCHHOFF'S CIRCUIT RULES

134 Note: Resistors must be isolated (disconnected from the circuit) before their resistances can be measured. This also prevents damage to the multimeter that may occur if a voltage is connected across its terminals while in the resistance mode. R Figure 7-7: Connec- tion of an ohm- meter to measure resistance. In the next activity, you will use the multimeter to measure the resistance of sev- eral resistors. You will need e several color-coded resistors e 2 digital multimeters ® 6-V battery Activity 1-3: Reading Resistor Codes and Measuring Resistance 1. Choose several resistors and read their codes. Record the resistances and the tolerances in the first two columns of Table 7-2. Table 7-2 R from Tolerance Measured Measured Measured R = V/I code (1)) from code R () V (V) 1 (A) Q) 23_N| +5% [22.8-1[3.L\V |00l A |92.40 5.0 | 25 [14 1303V 0.4ga [1S.00 290 |25 390 [3.w2V 0.093p (2890 ol | £51 Q@20 |3.02V |D03TA |971.80 There are two ways to determine resistance with the multimeter. One is to use the resistance mode and measure the resistance directly. The second is to connect the resistor to a battery and then measure the voltage across the resistor and the current through the resistor. R can then be calculated from Ohm’s law, R = V/I. You will use both of these methods to measure the resistances of the resistors you selected. 2. Measure the resistance of each of your resistors directly using the multimeter and enter the values in Table 7-2 under “Measured R.” 3. Be sure to reset the multimeter to measure current and voltage, respectively, or you will burn out the fuse in the meter. Connect each resistor to the battery and simultaneously measure the voltage across the resistor and the current through the resistor with the multimeters. Record V and I in the appropriate columns of Table 7-2 and calculate the resistance from these values. REALTIME PHYSICS: ELECTRICITY AND MAGNETISM i—

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Question 1-5: How do the values of your resistors measured with the resistance mode of the multimeter compare to the values indicated by the code? Assuming that your measured values are correct, are the values indicated by the code cor- rect within the stated tolerance? N ey were WY Close . e treu Are Question 1-6: How do the resistance values found from the voltage across the resistor and the current through it compare to the values measured with the re- sistance mode of the multimeter? Do you conclude that the resistance mode is reliable? Explain. qe ) J t “{(\(‘f* \/\'—’CJ | YO v : ) 2 WX \ ': .- ! ~.. C ¢ v i J ( s INVESTIGATION 2: SERIES AND PARALLEL COMBINATIONS OF < RESISTORS Several resistors can be wired in series or in parallel as shown in Figure 7-8. Series resistors Parallel resistors G- S p— R R, Figure'7-8: Resistors wired in series and in parallel. Prediction 2-1: Do you think that two identical resistors wired in'series will have a total resistance that is greater, the same as, or less than the individual resistance of one of them? / J\"\'Q( v To do some exploration of equivalent resistance of different resistors wired in com- bination you will need the following: e 3 51-) resistors e a22-() and a 75-() resistor ¢ digital multimeter s 6 alligator clip leads 135 LAB 7: KIRCHHOFF’'S CIRCUIT RULES

136 Uov ddd ~": Activity 2-1: Equivalent Resistance of Resistors Connected in Series 1. Measure the actual values of the 51-() resistors with the multimeter. Record their values below: R, 0.1 o R, 20D r,209 o 2. Connect R; and R, in series. Measure the resistance of this series combination with the multimeter. Resistance of Ry and R, in seriuszm_ﬂ 3. Now connect R;, R,, and Rj in series and measure the resistance of the com- bination. Resistance of Ry, Ry, and Rj in sories:lu(l Question 2-1: How did your measurements compare to your prediction? Yoey matoned, all ’\qu\r.\(‘( = o\ addead '{V‘QC”,.;#V’ Question 2-2: Based on your measurements, state a rule for finding the equivalent resistance of several resistors connected in series. If the resistors have resistances R;, R,, and Rj, write a mathematical equation for the equivalent re- sistance, Req, when these are connected in series. Explain how your measurements support this rule. 'e) E — D R, + R, ¥Ry = Beq Question 2-3: Does your rule agree with your observations in Lab 5 that the cur- rent through two identical resistors connected in series is half the current through a single resistor connected to the same battery? Explain. W Cey . Ged, 1€ You have resistors in seriey ~ Vo , « T (¢ them Togetner So eyl O Prediction 2-2: Do you think that two identical resistors \vued in pamllol will have a total resistance that is greater, the same as, or less than the individual resistance of one of them? less tnhan Test your prediction. Activity 2-2: Equivalent Resistance of Resistors Connected in Parallel 1. Use your three 51-{) resistors again. Connect R; and R, in parallel. Measure the resistance of this parallel combination with the multimeter. . 2C, 7] Resistance of Ry and R; in |)(|mllvl:/..-7- J,,,(l 2. Now connect Ry, Ry, and Rs in parallel, and measure the resistance of the com- bination. Resistance of Ry, Ry, and Ry in parallel: \1‘ 3 REALTIME PHYSICS: ELECTRICITY AND MAGNETISM L

Question 2-4: How did your measurements compare with your prediction? Jes Question 2-5: Based on your measurements, is the equivalent resistance, Req, consistent with the following mathematical relationship? \ \ Leieped Reglnetsmo Show the calculati(‘ms you used to check the validity of this equation. Req =(5dae 5081 Soge) = 161 Question 2-6: Does the relationship in Question 2-5 agree with your observa- tions in Lab 5 that the current through a battery connected to two identical resis- tors connected in parallel is twice the current through the battery when connected to a single resistor? Explain. Jes, becavse the resistance 1S \o\€ So corrent 1S dovle. 2-3: Other Combinations of Resistors in easure the values of the 22-Q and 75-() resistors with the multimeter. Record these values below: Ry— QO Rs— QO 2. Connect Ry, Ry, and Rs in series. Measure the resistance of this series combi- nation. Resistance of Ry, Ry, and Rs in series.— () //Question E2-7: Use your rule in Question 2-2 to calculate the equivalent resis- tance of these three resistors in series. Show your calculation. How does this value compare to the measured resistance of the series combination? 3. Connect Ry, Ry, and Rs in parallel. Measure the resistance of this parallel com- bination. Resistance of the combination:— () Question E2-8: Use the rule in Question 2-5 to calculate the equivalent resis- tance of these three resistors. Show your calculation. How does this value com- pare to the measured resistance of the parallel combination? 137 LAB 7: KIRCHHOFF'S CIRCUIT RULES

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

138 Now that you know the basic rules for calculating the equivalent resistance for series and parallel connections of resistors, you can tackle the question of how to find the equivalent resistance for a complex network of resistors. The trick is to be able to calculate the equivalent resistance of each segment of the complex network and use that in calculations of the next segment. For example, in the network shown in Figure 7-9, there are two resistance values, R; and R,. A series of simplifications is shown in the diagram below. Ry Ry R1 A R B LetRyj=R +Ry R3 R1 A ’_{ R, l—’\/\/\/—' B LetRy= RyRy/(Ry+ Ry Ry R, A ._/\/\/\/R—W\/—. B Where Roq= Ry + Ry 2 Figure 7-9: A sample resistor network. To complete the following extension about equivalent resistance you will need: e 3 22-Q) resistors e 3 51-() resistors e digital multimeter Extensioy{ 2-4: The Equivalent Resistance for a Network 1. Use the color-coded value for your smaller resistors for R, and the color-coded value for your larger resistors for R,. List these values below. Rypmo — Ry: 2. Calculate the equivalent resistance between points A and B for the network shown below. Show your calculations on a step-by-step basis. R, R, Eijigvvv Ry J -\ R A - B R/ AN —} i R/ REALTIME PHYSICS: ELECTRICITY AND MAGNETISM

3. Set up this network of resistors and check your calculation by measuring the equivalent resistance directly with the multimeter. Question E2-9: How did your measured value for the equivalent resistance agree with the calculated value? Could any disagreement be explained by the tolerances in the resistor values? Explain in detail. INVESTIGATION 3: KIRCHHOFF’S CIRCUIT RULES Consider a circuit that has many components wired together in a complex array. Suppose you want to calculate the currents in various branches of this circuit. The rules for combining resistors that you examined in Investigation 2 are very con- venient in circuits made up only of resistors that are connected in series or in par- allel. But, while it may be possible in some cases to simplify parts of a circuit with the series and parallel rules, complete simplification to an equivalent resistance is often impossible. This is especially true when additional components such as more than one battery are included. The application of Kirchhoff’s circuit rules can help you to understand the most complex circuits. Kirchhoff’s circuit rules are based on two conservation laws that apply to cir- cuits: conservation of charge and conservation of energy. Before summarizing these rules, we need to define the terms junction and branch in a circuit. Figure 7-10 illustrates the definitions of these two terms for an arbitrary circuit. As shown in Figure 7-10a, a junction in a circuit is a place where two or more wires are con- nected together. As shown in Figure 7-10b, a branch is a portion of the circuit in which the current is the same through all of the circuit elements. (That is, the circuit elements in a branch are all connected in series with each other.) Branch 1 Branch 2 Branch 3 4/(3Juncijion 1/\’;\ 48 R +| J + + + 12V —/— 6!2§ 6V 12V 6Q 6V — - ~ - - i + + 4V — 4V = ° _T Junction 2 (a) (b) Figure 7-10: An arbitrary circuit used to illustrate junctions and branches. Kirchhoff’s rules can be summarized as follows: 1. Junction Rule (based on charge conservation): The sum of all the currents entering any junction of the circuit must equal the sum of the currents leaving. 2. Loop Rule (based on energy conservation): Around any closed loop in a cir- cuit, the sum of all changes in pnlunti.ll (emfs and ]mh’nlid] drops across resistors and other circuit elements) must equal zero. LAB 7; KIRCHHOFF'S CIRCUIT RULES 139

These rules can be applied to a circuit using the following steps: 1. Assign a current symbol to each branch of the circuit, and label the cur- rent in each branch I, I, I, etc. 2. Arbitrarily assign a direction to each current. (The direction chosen for the current in each branch is arbitrary. If you choose the right direction, when you solve the equations, the current will come out positive. If you choose the wrong direction, the current will come out negative, indicating that its direction is actually opposite to the one you chose.) Remember that the current is always the same everywhere in a branch, and the current out of a battery is always the same as the current into a battery. 3. Apply the Loop Rule to each of the loops. a. Let the potential drop (voltage) across each resistor be the negative of the product of the resistance and the net current through the resistor. (However, make the sign positive if you are traversing a resistor in the direction opposite that of the current). b. Assign a positive potential difference when the loop traverses from the — to the + terminal of a battery. (If you are going across a battery in the opposite direction, assign a negative potential difference to the trip across the battery terminals.) Find each of the junctions and apply the Junction Rule to it. You can write currents leaving the junction on one side of the equation and currents com- ing into the junction on the other side of the equation. » To illustrate the application of the rules let’s consider the circuit in Figure 7-11. Arbitrarily assigned loop direction for keeping track of currents and potential differences Junction 1 Current direction through battery often chosen to be in the direction of —to + Loop 1 I R, Loop 2 ‘/lil' A — /,;/V Junchon 2 1 Figure 7-11: A complex circuit in which loops 1 and 2 share the resistor R. Question 3-1: Why aren’t the resistors R, and R, in series? Why aren’t they in pam”vl? ere. are 2 battery Jou n, Oets Cufent from koth VOl : Sou(Ces 140 REALTIME PHYSICS: ELECTRICITY AND MAGNETISM

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

In Figure 7-11 the directions for the loops through the circuits and for the three currents are assigned arbitrarily. That is, other assignments would work. If we assume that the internal resistances of the batteries are negligible, then by applying the Loop Rule we find that Loop 1 +& — LRy, — LRy =0 (1) Loop 2 —&3 + LRy — Ry =0 (2) By applying the Junction Rule to junction 1 or 2, we find that L=L+1 (3 (current into junction = current out of junction) It may trouble you that the current directions and directions that the loops are traversed have been chosen arbitrarily. You can explore this assertion by chang- ing these choices and analyzing the circuit again. (Alternate assignments if applied consistently will yield the same final results!) To do the next activity you’ll need the following;: ® 2 resistors (rated values of 39 and 75 Q) ¢ digital multimeter (to measure resistance) * 6-V battery ® very fresh, alkaline 1.5-V D cell battery and holder Activi& -1: Applying the Loop and Junction Rules Severaf {imes Figure 7-12 shows the same circuit as in Figure 7-11 with different arbitrary directions for the loops and current through R,. 4!; V T Loop1 |, Loop 2 Iy { | _J “AAA R1 R3 Figure 7-12: The same complex circuit as in Figure 7-11 with the current through R, chosen arbitrarily in the opposite direction, and the loops traversed in the coun- terclockwise direction instead of clockwise. 1. Use the loop and junction rules to write down the three equations for Figure 7-12 that correspond to Equations (1), (2), and (3) derived above for Figure 7-11. Question 3-2: Show that if you make the substitution I,’ = —1I,, then the three equations you just derived can be rearranged algebraically so they are exactly the ame as Equations (1), (2), and (3). LAB 7: KIRCHHOFF'S CIRCUIT RULES 141

142 2. Measure the actual values of the two fixed resistors of 75 and 39 (2 and the two battery voltages with your multimeter. List the results below. Measured voltage (emf) of the 6-V battery 1t Measured voltage (emf) of the 1.5-V battery £ Measured resistance of the 75-() resistor Rp: Measured resistance of the 39-() resistor Ry— 3. Carefully rewrite Equations (1), (2), and (3) with the appropriate measured (1ot rated) values for emf and resistances substituted into them. Use 100 (2 for the value of R, in your equations. You will be setting a variable resistor to that value soon. 4. Solve these three equations for the three unknown currents, I, I, and I3 in amps. Show your calculations in the space below. Question 3-3: Do your currents actually satisfy the equations? Use direct sub- stitution to find your answer. Now you can verify that the application of Kirchhoff’s rules actually works for this circuit. In addition to the materials from the previous activity, you will need: e 0 to 200-Q variable resistor (potentiometer) » 6 alligator clip leads Activity 3-2: Testing Kirchhoff’s Rules with a Real Circuit % Before wiring the circuit, use the resistance mode of the multimeter to mea- sure the resistance between the center wire on the variable resistor and one of the other wires. What happens to the resistance reading as you rotate the dial on the variable resistor clockwise? Counterclockwise? Set the variable resistor so that there is 100 ) between the center wire and one of the other wires. Was it difficult to do? If so, explain why. % REALTIME PHYSICS: ELECTRICITY AND MAGNETISM

w Wire up the circuit pictured in Figure 7-11 using the 0 to 200-() variable resistor set at 100 () as R,. Spread the wires and circuit elements out on the table so that the circuit looks as much like Figure 7-10 as possible. Use the multimeter to measure the current in each branch of the circuit (see Note below), and enter your data in Table 7-3. Compare the measured values to those calculated in Activity 3-1 by computing the percent difference inxead1 case. ’ Y Nf)fe: The most accurate and easiest way to measure the currents with the digital multimeter is to measure the voltage across a resistor of known value, and then use Ohm’s law to calculate I from V and R. Table 7-3 R measured w/ multimeter ()] V measured w/ multimeter V) Measured 1=V/R (amps) \ / 1) Thebretical / (@nps) (from Adtivity/3- % Difference Ry 9. (N 3.9V Jd A Y 30 Rz %A.2.9 2.43V o \&Fx /\ 3. Rs AN o2V « O5A T/ X X [ Question 3-4: Use your measured current values to verify the junction rule at the two junctions in the circuit. OoR LBA = 1| BA Question 3-5: Use your measured voltage values to verify the loop rule in loop 1 labeled in Figure 7-11. Quest valug _\_ o\ V< ~ differ by more than this? If you have LAB 7: KIRCHHOFF'S CIRCUIT RULES 1,105\ {1 3-6: How well do your measured currents agree u calculated in Activity 3-17 Are they within a few additional time, do the following extension. with the theoretical percent, or do they - (.em) (99 - (s\war) (4 LAY = - \2.00\4 143

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Extensjon 3-3: How Do Changes Affect the Currents? In Acfivities 3-1 and 3-2 you analyzed the circuit in Figure 7-11 with Kirchhoff’s N : ; . Loop Rule and Kirchhoff’s Junction Rule. Now consider the case where resistor R, is removed from the circuit. 1. Use the space to the right to draw a picture of the modified circuit (with Ry removed). Question E3-7: Wil the analysis of the modified circuit with Kirchhoff’s rules now be more or less complex than it was for the circuit in Figure 7-11? That is, will you need to generate more or fewer equations with Kirchhoff’s Loop Rule? With Kirchhoff’s Junction Rule? Why? Question E3-8: What is the effective value of R, in the modified circuit? Think about this question very carefully and explain. Prediction E3-1: Predict the values of the voltages across Ry and R; for the mod- ified circuit. Show your calculations clearly in the space below. Test your prudi(lion. Remove R, and measure [; and I5 from V3, V3, Ry, and R as before. Record the new values below. Vi Vy— . [i— - Iy Question E3-9: Did your observations agree with your predictions? Explain. REALTIME PHYSICS: ELECTRICITY AND MAGNETISM (4

UGS e leaving class Instructions: This sheet should be included as the last page of your lab work and printouts from the lab activity today. Before you leave class today you must discuss your answers with your teaching assistant, and receive guidance if necessary. Your teaching assistant will ini itial this page after your discussion. It is good to also discuss with another student if you are sharing a lab table. 1. Write down one major conclusion you can draw fr. don’t just list an equation. EQuVOLeNy FESISIAN CE 6F YESISIONS 1) SELILS 1S OO om this week's laboratory. Please explain concepts in words, TNANTR (CSISHANCE ofan ANQY (AQUAT YESTIN 1O TOWEL CaQUIvaIent (eg(sianice of YESISToS s DAY IS et -1 \a ] TR YES\SIGNTR D on individual resISTor. 2. What is the experimental evidence for this conclusion? Please ex, shows the above. Avoid answers such as “ explain/describe. Ln acHivily 72-1, adding anoiner RSiStoy MOCre0sea 1ine (CSIstance vy a factor of 2.+ fonowead (Gs= ‘ I OCHvit \ 2-7, (K ?g”t;r,\§>j anNe TR veSistancs plain in words what you saw and why it everything done in the lab” or “Activity 2-1,” you need to ey reHstor akcrealed - THollowed Cp= o, o Ql \? 2 3. Give one example of applications/situations for the finding(s) you described above in your everyday life outside of lab. - NNEN MAIcNg elecHrical Crircuity o o 11§ O DO YO SISTOFS 10 pOYaReL Wil Creat€ mMove Curven:- since T FESISTaNCE ARCIRASES, L O oG Nty 1N F IS Needed, fhen Poralel yenstors would need o e Useo, [ Question 1: is the conclusion appropriate (O—-1point) | - Question 2: does the evidence support the conclusion (0 -1 point) S Question 3: is the example reasonable (0~ 1 point) Total (0—3) Rev.:6/8/21

M3L7_GroupC11

Related Documents