LAB_15 - Capacitors and Inductors - No Quiz

LAB_15 - Capacitors and Inductors - No Quiz - Lab 15...

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Lab 15 163 Capacitors and Inductors Summary Capacitors and inductors are circuit components which are able to store and/or transfer energy in electrical circuits. Energy is stored in the electric field in the capacitor and the magnetic field around the inductor. These components come in a wide variety of configurations. In this experiment you will study the characteristics of some of these. Educational Objectives After performing this experiment, students should be able to: 1 . Measure the impedance (reactance) of an inductor. 2 . Measure the impedance (reactance) of a capacitor. 3 . Measure the time constant of an RC series circuit. 4 . Measure the time constant of an RL series circuit. 5 . Measure capacitance by observing charging and discharging times. 6. Measure inductance by observing charging and discharging time s. 7. Build a simple AC to DC Power Supply. "Genius is nothing but a greater aptitude for patience." - Benjamin Franklin (1706-1790)
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Lab 15 164 Background Information Capacitors Fundamentally, a capacitor consists of two isolated conductors. This definition is very general and does not require the conductors to have any particular shape or dimension. Each conductor could be an isolated wire, sheet or lump. When a voltage V is applied across the two conductors, a current briefly flows resulting in a charge of + Q on one conductor and an opposite charge of Q on the other. This charge separation is typically proportional to the applied voltage and allows us to define the capacitance C of the two isolated conductors as this proportionality constant. Q = CV - Definition of capacitance Figure 1a: Fundamental Definition of Capacitance From the definition, we see that capacitance is measured in coulombs per volt. In honor of the man who first studied them systematically, we define 1 Farad = 1 coulomb/volt. That is, the Farad is equal to one coulomb per volt. The separation of charge Q between the two conductors that compose a capacitor, creates an elec- tric field between them and results in the storage of energy. The amount of energy stored is: Conductor 2 Conductor 1 V + - - - - - - - - + + + + + + + + + - - E Q C CV C == 2 2 2 1 2
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Lab 15 165 Parallel-Plate Capacitor Some capacitors are made of two thin metal plates or sheets separated by an insulating (or dielec- tric) material. The two conductors are the top and bottom plates. Figure 1b: Parallel-Plate Capacitor For a parallel-plate capacitor (Fig. 1b) the value of the capacitance is dependent on the dielectric constant ε r of the medium between the plates, the area A of one plate, and the distance d between the plates: where: C is capacitance in Farads, A is the area of one side of one plate in square meters, d is the separa- tion of the two plates in meters and ε = ε
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This note was uploaded on 12/16/2011 for the course ENGR 102 taught by Professor Cattell during the Fall '10 term at Community College of Philadelphia.

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LAB_15 - Capacitors and Inductors - No Quiz - Lab 15...

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