Physics for Technology, Second Edition, 2nd Edition

Appendix B

Supplementary Lab Experiments

Contained in this appendix are ten laboratory experiments.

B.1   MEASURING LENGTH

Objective: To build and calibrate a device to measure length using a wire’s resistance dependence on length.

FIGURE B.1   A device to measure length using a wire’s resistance dependence on length.

Theory: A wire’s resistance changes with its length. By measuring the resistance of a wire of a known length, we can determine the wire’s resistivity ρ (the number of ohms per meter of wire). The resistance is given by:

$$\begin{array}{c}R=\rho \times L\\ \text{Resistance}\left(\Omega \right)=\text{resistivity}\left(\Omega \text{/m}\right)\times \text{length}\left(\text{m}\right)\end{array}$$

Once we know the wire’s resistivity, we can use the wire ...