chapter32

chapter32 - Chapter 32 Inductance L and the stored magnetic...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chapter 32 Inductance L and the stored magnetic energy RL and LC circuits RLC circuit Resistance, Capacitance and Inductance Ohms Law defines resistance: V R I Capacitance, the ability to hold charge: Q C V Capacitors store electric energy once charged: Resistors do not store energy, instead they transform electrical energy into thermo energy at a rate of: 2 2 V P V I I R R = = = ( 29 2 2 1 1 2 2 E Q U C V C = = Inductance, the ability to hold current (moving charge). Inductors store magnetic energy once charged with current, i.e., current flows through it. Inductance, the definition I When a current flows through a coil, there is magnetic field established. If we take the solenoid assumption for the coil: E E L + B nI = When this magnetic field flux changes, it induces an emf, E L , called self-induction: ( 29 ( 29 2 B L d NAB d NA nI d dI dI n V L dt dt dt dt dt = - = - = - = -- E or: L dI L dt R- E This defines the inductance L , which is constant related only to the coil. The self- induced emf is generated by current flowing though a coil. According to Lenz Law, the emf generated inside this coil is always opposing the change of the current which is delivered by the original emf. For a solenoid: 2 L n V = Where n : # of turns per unit length. N : # of turns in length l . A : cross section area V : Volume for length l . Inductor We used a coil and the solenoid assumption to introduce the inductance. But the definition holds for all types of inductance, including a straight wire. Any conductor has capacitance and inductance. But as in the capacitor case, an inductor is a device made to have a sizable inductance. L L dI dt R- E An inductor is made of a coil. The symbol is Once the coil is made, its inductance L is defined. The self-induced emf over this inductor under a changing current I is given by: L dI L dt = - E Unit for Inductance The SI unit for inductance is the henry (H) Named for Joseph Henry: 1797 1878 American physicist First director of the Smithsonian Improved design of electromagnet Constructed one of the first motors Discovered self-inductance A s V 1 H 1 = Discussion about Some Terminology Use emf and current when they are caused by batteries or other sources...
View Full Document

This note was uploaded on 05/06/2008 for the course PHYS 1304 taught by Professor Ye during the Spring '08 term at SMU.

Page1 / 22

chapter32 - Chapter 32 Inductance L and the stored magnetic...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online