Ohms Law

# Ohms Law - PHY 132 LAB : Ohm's Law Introduction: In this...

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PHY132 Labs (Bennett, JCHS) -1- 09/22/06 PHY 132 LAB : Ohm’s Law Introduction: In this lab, we look at the concepts of electrical resistance and resistivity. Text Reference: Young & Freedman 25:2-3. Special equipment notes: 1. Note the tips on wiring and meters attached at the end of this lab. That sheet is useful for other labs as well. 2. The DC supply includes a current-limit safety feature. You cannot exceed a set value, and a front-panel light will come on. Avoid this. Also, since this is a “constant voltage” supply, you should find voltage readings to be quite steady, while current readings may vary with contact resistance, etc. Theory: Ohm’s law states that the voltage drop V (volts) across a resistor R (ohms) is proportional to the current flow I (amps), namely V = IR eq. 1 A sample that follows this equation is said to be “ohmic”. The resistance of a cylindrical conductor is R = ρ L/A, eq. 2 where L and A are the length and cross-sectional area of the conductor, and ρ is the resistivity of the conducting material. Resistivity is a material property (like density), which is independent of size or shape. It can be seen that the units of resistivity are ohms * length, conventionally ohm-cm. Procedure: Part 1: (I, V) for carbon resistor. 1. Find the nominal value of R, based on the color code. 2.

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## This note was uploaded on 05/11/2008 for the course PHY 132 taught by Professor Tsen during the Fall '08 term at ASU.

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Ohms Law - PHY 132 LAB : Ohm's Law Introduction: In this...

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