DC Electric currents I Lab Report PDF

Preview

Summary

My detailed lab reports from Physics 2 Lab with Dr. Sorci....

Description

Expe r i me nt3:DCEl e c t r i cCur r e nt sI Fe br u a r y25,201 6

I. PURPOSE The purpose of the experiment is to learn how to set up basic circuits with resistors in series and in parallel and to measure current and voltage in order to very Ohm’s Law. II. THEORY Ohm’s Law states that the potential difference (V) is directly proportional to the current across the resistor. A resistor (R) impedes the current flow while simultaneously acting to lower voltage levels within the circuit. Resistors in series can be added together to get the equivalent resistance; however, resistors in parallel are added in the inverse (1/R). Voltage provides a charge in electrical potential energy and this causes the charge to flow (current). Like all potential energy, electrical potential energy wants to go from high to low EPE. The amount of current that flows through a resistor depends on what battery is attached to it. The amount of resistance a resistor has can be determined by the color bands painted on the outside of the resistor. The first 3 color bands are referred to as A, B, and C. Each color refers to a different digit. The D-band (fourth band) will be either silver or gold and indicates the tolerance of resistance. Silver is +/-10% while gold is +/-5%. If there is no band present, the tolerance of the resistance value is 20% For resistors in series that are not equal, the voltage across the resistors is not the same but the current is the same. Resistors in parallel that are not equal have the same voltage but different currents across them. Ohm’s Law:

Resistors in Series:

Resistors in Parallel:

Value of Resistor:

III. PROCEDURE Single Resistor

1. Record colors on resistor and determine value of the resistance. 2. Set up circuit using digital meter as ammeter to measure current and voltage. mA and com will be used for ammeter and V and COM will be be used for voltage. 3. Start recording. Adjust knob to 0.5V and record current and voltage. 4. Increase by 0.5V until you reach 5V. Record current for each interval.

Parallel and Series Circuits 1. Connect voltage sensor (port A) and current sensor (port B) to the 850. 2. Open Capstone. Choose 2 digits and graph display. 3. Choose set up hardware and click on A and choose voltage sensor. 4. Click on B and choose current sensor. 5. Click orange push pin on top of box. 6. Select voltage for the measurement on the y-axis of the graph and current for the xaxis. One digit should be current and the other should be voltage. Series Circuit

1. Set up circuit. 2. Hit Record. 3. Turn on power supply. Gently increase voltage to 5V. 4. Use icon with line and dots to perform a linear fit. Record slope. 5. Measure voltage and current over each resistor at 5V. Parallel

1. Set up circuit. 2. Hit Record. 3. Turn on power supply. Gently increase voltage to 5V.

4. Use the icon with lien and dots to perform a linear fit. Record slope. 5. Measure voltage and current over each resistor. 6. Measure voltage and current over each resistor at 5V.

During the course of this experiment, I assisted my lab partners in setting up the circuit. In addition, I recorded measurements and worked out my own calculations. V. ANALYSIS

VI. CONCLUSION This experiment confirmed Ohm's through various situations. For the single resistor set-up, the theoretical total resistance was calculated to be 2680 while the slope of the graph was 3493.3. This gave a percent error of 5.07%. For the experiment with the resistors in series, the theoretical total resistance was calculated to be 380. One resistor was 220 while the other was 160. The value from the slope of the graph was 396, resulting in a percent error of 4.21%. The measured voltage for the 160 resistor was 2.76 and for the 220 resistor was 2.24. The current throughout both resistors was the same, as expected. The calculated theoretical current for the resistors in series was calculated to be 13.18mA, giving a percent error of 2.57%. The theoretical voltage across the 160 resistor was calculated to be 2.208V, giving a percent error of 25.00%. The theoretical voltage across the 220 resistor was calculated to be 3.036V, giving a percent error of 1.45%. For the experiment with the resistors in parallel, the theoretical total resistance was calculated to be 92.63. One resistor was 220 while the other was 160.The value from the slope of the graph was 97.9, giving a percent error of 5.70%. The measured current for the 160 was measured to be 27.7mA and for the 220 was 22.5mA. The voltage throughout both resistors was the same, as expected. The calculated theoretical voltage for the resistors in series was calculated to be 4.99V, giving a percent error of 1.603%. The theoretical current across the 160 resistor was calculated to be 31.25mA, giving a percent error of 11.36%. The theoretical current across the 220 resistor was calculated to be 22.73V, giving a percent error of 1.01%. The total current theoretical current was calculated to be 53.98mA while the

actual current across both resistors was totaled at 50.21mA. This gave a percent error of 7.00%. Although there was some minor error and one particularly high percent error, this experiment can be considered a success. This high percent error is likely due to human error that could have been caused by not reading or recording the correct value. In addition, this high percent error could have been caused by faulty equipment. Our ammeter blew a fuse and data that came from that machine on previous readings could have been slightly skewed....