Resistance and Electric Circuits

Topics: Electrical resistance, Resistor, Electrical impedance Pages: 3 (714 words) Published: March 27, 2011
Resistance and Electric Circuits|
Lab 5|

The goal of the “Resistance and Electric Circuit” Lab was to determine the resistivity of a conducting wire given two known resistors. The main property of resistivity is that it represents how easily electrons can flow through a material. A Galvanometer is used to measure the current of the circuit and the Wheatstone Bridge is used to measure the resistances and determine the unknown resistance. This experiment also relates Ohm’s Law to determine the resistivity using the resistance of the wire, length of the wire, and cross sectional area. In order to relate a measured resistance as a function of length and obtain the value for an unknown resistor, a Wheatstone Bridge must be attached to a dc power supply, and a galvanometer. In order to determine the correct value for the known resistance, the galvanometer must read zero. Second, to relate the resistance to a specific length a micrometer is used in connection to a variable resistance box. Use six difference lengths on the micrometer, we chose intervals of 10, starting at 10 centimeters and ending at 60 centimeters. For the first set of data points, drag the micrometer tab to rest on 10 centimeters (have the same person press down on the wire for every data point using the same force because a change in force on the wire could vary the results). Then, using the variable resistor box, increase the resistance of the box until the galvanometer reads a value of zero. When the galvanometer reads zero the resistance shown on the variable resistance box is the unknown resistance relating to the specific length on the wire. Repeat these steps for five more values on the micrometer. After conducting, the experiment using a known R1 of 100Ω and R2 of 10Ω several data points were obtained and a line graph was formatted to relate the Resistance (R) and Length (L): Length (m)| R3 (Ω)| R3/10= R (Ω)|

.1| 26| 2.6|
.2| 70| 7|
.3| 104| 10.4|...
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