tailieunhanh - Lecture Electric circuits analysis - Lecture 25: Capacitors and Inductors

Lecture Electric circuits analysis - Lecture 25: Capacitors and Inductors. In this chapter, the following content will be discussed: Introduction, capacitors, series and parallel capacitors, inductors, series and parallel inductors. | Capacitors and Inductors Introduction Capacitors Series and Parallel Capacitors Inductors Series and Parallel Inductors Lecture 25 Introduction Resistor: a passive element which dissipates energy only Two important passive linear circuit elements: Capacitor Inductor Capacitor and inductor can store energy only and they can neither generate nor dissipate energy. Capacitors A capacitor consists of two conducting plates separated by an insulator (or dielectric). When a voltage source v is connected to the capacitor, the source deposits a positive charge q on one plate and a negative charge −q on the other. The capacitor is said to store the electric charge. Capacitance The amount of charge that a capacitor can store per unit of voltage across its plates is its capacitance, designated C. That is, capacitance is a measure of a capacitor's ability to store charge. The more charge per unit of voltage that a capacitor can store, the greater its capacitance, as expressed by the following formula: By rearranging the terms C=Q/V, we can obtain two other formulas. Q= CV V= Q /C The Unit of Capacitance The farad (F) is the basic unit of capacitance. Recall that the coulomb (C) is the unit of electrical charge. One farad is the amount of capacitance when one coulomb (C) of charge is stored with one volt across the plates. Although the capacitance C of a capacitor is the ratio of the charge per plate to the applied voltage v, it does not depend on q or v. Three factors affecting the value of capacitance: Area: the larger the area, the greater the capacitance. Spacing between the plates: the smaller the spacing, the greater the capacitance. Material permittivity: the higher the permittivity, the greater the capacitance. Circuit symbols for capacitor According to the passive sign convention, current is considered to flow into the positive terminal of the capacitor when the capacitor is being charged, and out of the positive terminal when the capacitor is discharging. Polyester . | Capacitors and Inductors Introduction Capacitors Series and Parallel Capacitors Inductors Series and Parallel Inductors Lecture 25 Introduction Resistor: a passive element which dissipates energy only Two important passive linear circuit elements: Capacitor Inductor Capacitor and inductor can store energy only and they can neither generate nor dissipate energy. Capacitors A capacitor consists of two conducting plates separated by an insulator (or dielectric). When a voltage source v is connected to the capacitor, the source deposits a positive charge q on one plate and a negative charge −q on the other. The capacitor is said to store the electric charge. Capacitance The amount of charge that a capacitor can store per unit of voltage across its plates is its capacitance, designated C. That is, capacitance is a measure of a capacitor's ability to store charge. The more charge per unit of voltage that a capacitor can store, the greater its capacitance, as expressed by the following .