Were your predictions for the currents within 10% of the measured values? If your predictions were clearly wrong, what mistaken assumption did you make in your calculations? Percentage Error= | [(Measured Value - Predicted Value)/ Predicted Value)] | x100% For 11: Percentage Error= | [(8.56mA - 27.3mA) / 27.3mA)] |x100% = 68.6% For 12: Percentage Error- | [(8.61mA - 60.0mA) / 60.0mA)] |x100% = 85.7% For It: Percentage Error- | [(8.45mA - 18.1mA) / 18.1mA)] |x100% -53.3% No, because instead of using the voltage at each resistor we use +ve total voltage to calculate the current at each resistor. 3. Using two multimeters, connect ammeters 1 and 2 from the previous diagram so that you can read the currents simultaneously. Reverse the connections to ammeter 1 to see what the ammeter reads when inserted "backwards" into the circuit. 11 = -8.72 mA Explain the reading you obtain. First the two ammeters read the same I being equal to 8:72 mA, after reversing the connections to ammeter 1, they still measure the same value of I but this time with opposite signs. In fact, ammeter 1 reads a negative value of I being equal to -8.72 mA.c) Discuss how the voltage changes follow Kirchhoff's loop rule. Kirchoff's loop rule states that the sum of all electric potential differences/voltages around a loop in a circuit is 0. The voltage changes, as recorded from the lab experiment, were measured at a value close to 0, which means with the effect of some lab errors, the voltage changes respect Kirchoff's loop rule. Check your understanding An ammeter and a voltmeter are connected in B various ways to a non-ideal battery having an internal resistance of r: In which diagram(s) does the ammeter correctly measure the current through R R the battery? ii) In which diagram is the current through the battery nearly zero? iii) In which diagram(s) does the ammeter CI + correctly measure the current through the resistor with resistance R? A iv) In which diagram does the voltmeter correctly measure the terminal voltage of the battery? R . R V) In which diagram does the voltmeter read almost zero? viy In which diagram(s) does the ammeter read almost zero?5. Remove one of the ammeters from the circuit and switch it to be a voltmeter. For each part of the path around the circuit, measure and record on the diagram the potential difference. Include the sign of each potential difference. To measure a potential difference, simply touch the two leads of the voltmeter to the two points between which you want to measure AV. A voltmeter will read a positive value if the "+" lead touches a higher potential than the "-" lead. Record the current flowing in the circuit. 1 - -8.79mA If AV reads less than 2 V. adjust the voltmeter to read on the "2 volt max" range. AV :209 AVwire 22092 AV power supply AV wire = Avpow 10052 AV 1900 AV 22082 - er AV 10082 AVam AV 33092 meter 3309 AV ammeter = AV 1398 V power supply: -5.93 V V wire: 5.93 V V 220 ohm: -1.96 V V 100 ohm: 0.89 V V 330 ohm: -2.96 V V ammeter: 0.81 V7. When you attach the voltmeter in parallel across a resistance, why doesn't the ammeter reading change? The ammeter reading doesn't change when the voltmeter is connected in parallel across a resistance because of a few reasons; the ammeter measures the total current in the circuit, which includes both the main current through the resistance and the small current through the high-resistance voltmeter. The small current through the voltmeter is Physics 203-NYB-05 Electricity & Magnetism Lab #1b: Introduction to multimeters negligible and doesn't really affect/change the ammeter reading. 8. Conclusion Answer the following questions on the following page: a) Discuss how a voltmeter should be connected in a circuit so that the circuit, within experimental uncertainties, remains unchanged. Explain why it does not affect the circuit when properly connected. b) Discuss how an ammeter should be connected in a circuit so that the circuit, within experimental uncertainties, remains unchanged. Explain why it does not affect the circuit when properly connected. c) Discuss how the voltage changes follow Kirchhoff's loop rule. Kirchoff's loop rule states that the sum of all electric potential differences/voltages around a loop in a circuit is 0. The voltage changes, as recorded from the lab experiment, were measured at a value close to 0, which means with the effect of sYou are provided with a 100-ohm carbon resistor, a 220-ohm carbon resistor, and a 330-ohm carbon resistor. The resistors are color coded to indicate both their approximate resistance (the first three colored bands) and the tolerance or uncertainty in this approximate resistance (the fourth colored band): bow Hack how sl v 10% silver 10% brown god 5% god 5% 220 0 carbon resistor 100 0 carbon resistor RESISTORS IN SERIES Assemble the series circuit made up from a power supply, set at about 6 V, three resistors and a voltmeter. Before switching on the power supply, have your instructor check the circuit. A wrong connection can blow a fuse or damage the meter. 22092 1predicted = VT 10092 VTmeasured = 33092 3predicted = 2predicted =Introduction This lab experiment is intended to provide experience in using multimeters for measuring and analyzing simple circuits. The accurate measurements possible with these devices complement your other experiments with circuits. Objective To investigate energy conservation and current conservation in a series circuit. METERS You should have two multifunction meters ("multimeters") that can serve as voltmeters for measuring potential differences, as ammeters for measuring current, or as ohmmeters for measuring resistances, depending on how the switches on the meter are set (some multimeters also require changing from ammeter sockets to voltmeter sockets). An ammeter has very low resistance (ideally zero) and should not affect the current you are trying to measure. Of course any real ammeter that is inserted into a | circuit does have some resistance. The voltmeter used in this experiment can be thought of as a very sensitive ammeter in series with a very large (known) resistance R. When you connect the voltmeter between two points that have different potentials, a tiny current I runs through the voltmeter, and the amount of current is an indication of the potential difference (AV = RI). In many practical situations this current is so small that attaching the voltmeter hardly affects the operation of the circuit. KIRCHHOFF'S RULE FOR ENERGY CONSERVATION In any circuit, energy conservation yields a loop: Loop Rule { V = 0, around any loop (or V.supplied - Vused = 0) You will verify that this equation correctly describes a circuit. In the process you will practice U6. Energy conservation on a per-charge basis predicts that the individual potential differences should add up to zero for a round trip around the circuit. Do your values confirm this prediction? Voltages add up to -8.64V which shows that there were error sources affecting the measurements. Justify your answer; use your values and calculate: (a) AV supplied - used - V power supply: -5.93 V V wire: 0.00 V V 220 ohm: -2.96 V V 100 ohm: 0.89 V V 330 ohm: -3.66 V V ammeter: 0.81 V -5.93V - (0.00V -2.96V +0.89V -3.66V +0.81V)= -1.01V (b) AV supplied Abused x 100 = AV supplied AV -UPDied: -5.93V AV supplied: -4.92V ((-5.93V - (-4.92)) /-5.93) x 100= 17.0%\f3. Using two multimeters, connect ammeters 1 and 2 from the previous diagram so that you can read the currents simultaneously. Reverse the connections to ammeter 1 to see what the ammeter reads when inserted "backwards" into the circuit. 11 = -8.72 mA Explain the reading you obtain. First the two ammeters read the same I being equal to 8.72 mA, after reversing the connections to ammeter 1, they still measure the same value of | but this time with opposite signs. In fact, ammeter 1 reads a negative value of I being equal to -8.72 mA. This means the current can still flow in the opposite direction. In fact, the polarity is now heading in the negative direction. Physics 203-NYB-05 Electricity & Magnetism Lab #1b: Introduction to multimeters 4. Switch ammeter 1 to be a voltmeter reading a positive value but do not change its position in the circuit (some multimeters may also require changing from ammeter sockets to voltmeter sockets). Original readings 1, = 8.72 mA 12 = 8.72 mA Switched readings V1 = 5.93 V 12 = 0.01 mA When you switch the ammeter 1 to be a voltmeter, why does the ammeter reading change? Explain clearly. A voltmeter acts like a huge resistor, which results in the decrease of current. As the ammeter's rule is to measure the current, it will read 0 mA ideally.2. Using one ammeter at time, at the places shown in the diagram, measure the current in such a way that the ammeters will read positive values. An ammeter will read a positive value if conventional current flows into the terminal marked "+". Choose the ammeter scales to give maximum accuracy. Record the ammeter readings on the diagram. 1 measured 22052 A1 10082 A3 33092 3measured = 12measured = Physics 203-NYB-05 Electricity & Magnetism Lab #1b: Introduction to multimeters Limeasured: 8.56mA [2measured: 8.61mA 3measured: 8.45mA Were your predictions for the currents within 10% of the measured values? If your predictions were clearly wrong, what mistaken assumption did you make in your calculations?1. Measure the voltage of the power supply. VT = 5.95 V Predict the currents 11, 12 and I; that will flow in the circuit. Calculations for the Predicted Intensities: 1. 2 . 3. V= IR V=IR V= IR 1= V/R I= V/R I= V/R V=6V V= 6V V= 6V R= 220n R= 1000 R= 330n |1= 6V/2200 12= 6V/100g la= 6V/330g 11= 0.0273A 12= 0.0600A 13= 0.0181A Liaradicted = 27.3 mA 2predicted = 60.0mA 3oradicted = 18.1mA Note the units are in milli-ampere (mA = x10-3 A). 2. Using one ammeter at time, at the places shown in the diagram, measure the current in such a way that the ammeters will read positive values. An ammeter will read a positive value if conventional current flows into the terminal marked "+". Choose the ammeter scales to give maximum accuracy. Record the ammeter readings on the diagram. 22012 1 measured