BME 153 lab 2 Ohm's law and power _Nigel

# BME 153 lab 2 Ohm's law and power _Nigel - BME 153 Lab 3...

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Lab 2 – Ohm’s Law and Power Nigel Chou Shijie Lab Partner: Tim Liu Section 1 September 12, 2007 I have adhered to the Duke Community Standard in completing this assignment. _____________________________ Objectives The objective of this lab is learn to measure current using a digital multimeter, and to demonstrate Ohm’s law, first by showing how the current calculated by Ohm’s law correspond to values of current measured directly, then by exploring the i - v relationships of various resistors. We also learned how to measure power indirectly with voltage and resistance measurements. Using the breadboard, we also learned to construct two voltage divider circuits. We studied the relation of power dissipation to resistance in the first circuit, and the variation of voltage with resistance in a slightly more complicated circuit. Apparatus BK Precision 1652 Triple Output DC Power Supply Fluke 45 Dual Display Bench Multimeter / Digital Multimeter (DMM) Potentiometer Various Resistors Solderless breadboard Procedure 1. Current : The circuit shown in figure 1 was assembled, with the power supply set to 5V and the negative side connected to the frame ground of the power supply. The current through each resistor was first determined by measuring the voltages across them and using ohm’s law, then measured directly. The DMM was used for both voltage and current measurements. 2. Ohm’s law : The current through 3 resistors (560 , 1000 , 2200 ) is measured as the source voltage is varied from 1 to 10V. The Voltage is then plotted against current for each resistor. 3. Power : Using the circuit in Figure 2, 7 to 10 measurements of V out are taken over varying resistances of the potentiometer, then the Voltages and resistances measured are used to calculate power, which is plotted against the resistance of the potentiometer. Separate tests are done for a source voltages of 8V,10V and 12V. 4. Voltage divider : The circuit in Figure 3 was set up, with R 1 and R 2 set as close as possible to the values calculated in the Prelab. For R1, a 120 resistor was used in place of the 133.3 resistor. For R 2 , two resistors, one 2000 and another 510 were used in series to simulate the 2533.3 resistor. 10 measurements of V out were made for various resistance values (R 3 ) of the potentiometer, then V out was plotted against R. Data and Calculations The uncertainty for the DMM when measuring resistance is 0.05% of reading + 2 digits, where digits refers to the least significant digit of the reading. The uncertainty for current is 0.2% of reading + 5 digits. Uncertainty when measuring voltage is 0.25% of reading + 6 digits.

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## This lab report was uploaded on 04/09/2008 for the course BME 153 taught by Professor Malkin during the Fall '07 term at Duke.

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BME 153 lab 2 Ohm's law and power _Nigel - BME 153 Lab 3...

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