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Chapter 3. Inductance and Capacitance. Capacitance. Capacitor - a circuit component that has two parallel metal plates separated by a dielectric 3D Drawing Circuit Symbols. Capacitance - the measure of the ability of a capacitor to store charge Voltage Equation for a Capacitor v=q/C
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Chapter 3 Inductance and Capacitance
Capacitance • Capacitor - a circuit component that has two parallel metal plates separated by a dielectric • 3D Drawing • Circuit Symbols
Capacitance - the measure of the ability of a capacitor to store charge • Voltage Equation for a Capacitor v=q/C C = Capacitance in Farads (F) q = Charge on one plate in Coulombs (C) v = Voltage across the capacitor in Volts (V) Example: What is the charge on a 200mF capacitor with 100 Volts across its terminals?
Examples: (Plots of v and i) • What is the current to the 100mF capacitor for the following voltages? • v = 9 Volts • v(t) = 9V sin((200rad/s) t) • v(t) = 9V cos((200rad/s) t)
Capacitance Equation eo = permittivity of air, 8.85 x 10-12 F/m er = relative permittivity of the dielectric (Table 3.1) A = plate area in square meters (m2) d = distance between plates in meters (m)
Capacitor Applications • Keyboards • Surge Suppressors • Radio Tuners • Camera Flash Units
Types of Capacitors • Electrolytic • Oil-filled • Ceramic • Variable Capacitors • How can you vary the capacitance of a capacitor?
Capacitors in Series • Draw three capacitors in series with a battery. • What is the same for every capacitor in a series? • Answer: Charge • This leads to the Total Capacitance Equation:
Capacitors in Parallel • Draw three capacitors in parallel with a battery. • What is the same for every capacitor in parallel? • Answer: Voltage • This leads to the Total Capacitance Equation:
Inductance • Inductor - a circuit component that has two terminals connected to a coil of wire • Inductors are also called: • Solenoids • Coils • Electromagnets • 3D Drawing • Circuit Symbols
Inductors in Series • What is the same for every inductor in a series? • Answer: Current • This leads to the Total Inductance Equation:
Inductors in Parallel • What is the same for every inductor in parallel? • Answer: Voltage • This leads to the Total Inductance Equation:
Inductance (L) is the measure of an inductors ability to impede current using a magnetic field • It is measured in Henries (H). • What does the inductance of an inductor depend upon? • Answers: Length, Diameter, Core Material, Number of Turns of Wire
Energy Stored on a Inductor • Inductors also do not dissipate energy like resistors. • They store energy in the form of a magnetic field.
Energy Stored on a Capacitor • Capacitors do not dissipate energy like resistors. • They store energy in the form of charge. DEMO
Examples: (Plots of v and i) • What is the voltage across a 10mH inductor for the following currents? • i = 10 A • i(t) = 10A sin(200t) • i(t) = 10A cos(200t)
Exam I • Thursday • Use the study guide on the course home page • Graded Homework
Example Problem • What is the capacitance of a capacitor with plates with an area of 1 cm2 used to sandwich a polystyrene (er=2) sheet 0.1 mm thick.