Ohms Law and Electric Power Fall 2018.pdf - Ohms Law Electric Power Part 1 Ohms law Introduction and Theory Text reference Young Adams and Chastain 19.2

Ohms Law and Electric Power Fall 2018.pdf - Ohms Law...

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Ohm’s Law. Electric Power Part 1. Ohm’s law. Introduction and Theory: Text reference: Young, Adams, and Chastain §19.2. Ohm’s Law states that the voltage drop V (volts - V) across a resistor R (ohms - ) is proportional to the current flow I (amperes - A), namely ࠵? = ࠵? ∙ ࠵? (1) A sample that follows this equation is said to be “ohmic”. The resistance of a cylindrical ohmic conductor is ࠵? = ࠵?࠵? ࠵? (2) where L and A are the length and cross-sectional area of the conductor respectively, and ρ is the resistivity of the conducting material. Resistivity is a material property (like density), which is independent of size or shape. Procedure Part 1a: Current – voltage ( I - V ) characteristic for a carbon resistor 1. Find the nominal value of the carbon resistor’s resistance R (the one on the plastic holder), based on the color code. 2. Measure the resistance R of the carbon resistor using the ohms range of the Digital Multimeter (DMM). The resistor must be out of the circuit! 3. Connect the circuit shown in Fig. 1 below. Fig. 1. Circuit diagram. Technical note : meters can influence sensitive circuit measurements. Namely, the current through the ammeter includes both the sample and voltmeter currents. The voltmeter however, draws negligible current for the samples we use. 4. Tabulate ( I - V ) data in the range 0 – 15 Volts. Take data one way only (the way up): 7 points total. The (0, 0) is recommended to be included as a by-default point.

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