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Capacitors (5.1); Inductors (5.2); LC Combinations (5.3). Dr. Holbert November 6, 2001. Energy Storage Elements. Capacitors store energy in an electric field. Inductors store energy in a magnetic field. Capacitors and inductors are passive elements: Can store energy supplied by circuit
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Capacitors (5.1); Inductors (5.2); LC Combinations (5.3) Dr. Holbert November 6, 2001 ECE201 Lect-19
Energy Storage Elements • Capacitors store energy in an electric field. • Inductors store energy in a magnetic field. • Capacitors and inductors are passive elements: • Can store energy supplied by circuit • Can return stored energy to circuit • Cannot supply more energy to circuit than is stored. ECE201 Lect-19
Power Generation and Distribution • Energy storage elements model electrical loads: • Capacitors model computers and other electronics (power supplies). • Inductors model motors. ECE201 Lect-19
Signal ProcessingCommunicationInstrumentation • Capacitors and inductors are used to build filters and amplifiers with desired frequency responses: • Instrumentation amplifiers. • Capacitors are used in analog-to-digital (A/D) converters to hold a sampled signal until it can be converted into bits. ECE201 Lect-19
Solid StateDigital Design • Integrated circuits (ICs) have layers of conductors (metal, silicon with impurities) with insulators (glass) between. This is a capacitor! • This capacitance is one of the limiting factors in processor speeds. • This capacitance is used to create RAM’s. ECE201 Lect-19
Electromagnetics • For high frequency signals, inductance and capacitance are more significant effects than resistance. ECE201 Lect-19
Capacitance • Capacitance occurs when two conductors (plates) are separated by a dielectric (insulator). • Charge on the two conductors creates an electric field that stores energy. + + + + + + + + +- - - - - - - - - - - - ECE201 Lect-19
Capacitance • The voltage difference between the two conductors is proportional to the charge: q = Cv • The proportionality constant C is called capacitance. • Units of Farads (F) – Coulomb/Volt ECE201 Lect-19
The rest of the circuit + i(t) v(t) – Capacitor ECE201 Lect-19
Capacitor Voltage ECE201 Lect-19
Energy Stored ECE201 Lect-19
Class Examples • Learning Extension E5.2 • Learning Extension E5.3 ECE201 Lect-19
Inductance • Inductance occurs when current flows through a (real) conductor. • The current flowing through the conductor sets up a magnetic field that is proportional to the current. • The voltage difference across the conductor is proportional to the rate of change of the magnetic field. ECE201 Lect-19
Inductance • The voltage difference across the inductor is proportional to the rate of change of the current. • The proportionality constant is called the inductance, denoted L • Units of Henrys (H) - V·s/A ECE201 Lect-19
Inductor The rest of the circuit + i(t) H v(t) – ECE201 Lect-19
Inductor Current ECE201 Lect-19
Energy Stored ECE201 Lect-19
Class Examples • Learning Extension E5.4 • Learning Extension E5.5 ECE201 Lect-19
Inductor Combinations • Series inductors combine like series resistors Lser = L1 + L2 + L3 + · · · • Parallel inductors combine like parallel resistors 1/Lpar = 1/L1 + 1/L2 + 1/L3 + · · · ECE201 Lect-19
Capacitor Combinations • Series capacitors combine like parallel resistors (opposite) 1/Cser = 1/C1 + 1/C2 + 1/C3 + · · · • Parallel capacitors combine like series resistors (opposite) Cpar = C1 + C2 + C3 + · · · ECE201 Lect-19
Class Examples • Learning Extension E5.7 • Learning Extension E5.8 ECE201 Lect-19