Electromagnetic Field Theory
Lecture 5
Electromagnetic Field Theory
“Our thoughts and feelings have Dr. G. V. Nagesh Kumar Professor and Head, Department of EEE, electromagnetic reality. JNTUA College of Engineering Pulivendula Manifest wisely.” Topics
1. Magnetic circuits, MMF, Reluctance 2. Self and Mutual inductance of simple configurations
3 MMF
• Definition: The current flowing in an electric circuit is due to the existence of electromotive force similarly magnetomotive force (MMF) is required to drive the magnetic flux in the magnetic circuit. • The magnetic pressure, which sets up the magnetic flux in a magnetic circuit is called Magnetomotive Force. • The SI unit of MMF is Ampere-turn (AT), and their CGS unit is G (gilbert). • In short, a force which is responsible to drive flux in the magnetic circuit (same as electromotive (EMF) which drives electron in an electric circuit) is known as magnetomotive force .
4 MMF
• The strength of the MMF is equivalent to the product of the current around the turns and the number of turns of the coil. • As per work law, the MMF is defined as the work done in moving the unit magnetic pole (1weber) once around the magnetic circuit. • The MMF is also known as the magnetic potential. • It is the property of a material to give rise to the magnetic field. • The magnetomotive force is the product of the magnetic flux and the magnetic reluctance.
5 Reluctance
6 Reluctance
• The reluctance (S), of a material is a measure of how difficult it is to produce flux within it. • It represents the opposition to magnetic flux, and depends on the geometry and composition of an object. • Permeability, on the other hand, is a measure of how easily a magnetic field can be set up in a material. • Permeability is the ratio of the flux density of the magnetic field within the material, to its field strength. • To produce a magnetic circuit with low reluctance, the circuit length should be kept short, the material chosen for the magnetic circuit should have a high permeability and the cross sectional area of the circuit should be large.
7 Reluctance
8 Similarities
9 Inductance
10 Inductance of Toroid
11 Inductance of Solenoid
12 Inductance of Coaxial Cable
13 Mutual Inductance
14 Mutual Inductance
15 Mutual Inductance
16 Inductance
17 Magnetic Energy
18 Magnetic Boundary Conditions
19 Boundary Conditions for Normal Component
20 Boundary Conditions for Normal Component
21 MagneticBoundary Conditions Boundary for Conditions Tangential Component
22 MagneticBoundary Conditions Boundary for Conditions Tangential Component
23 MagneticBoundary Conditions Boundary for Conditions Tangential Component
24 Boundary Conditions
25 Problem
26 Problem
27 Problem
28 Problem
29 Problem
30 Problem
31 Problem
32 Problem
33 Problem
34 Problem
35 Problem
36 Problem
37 Problem
38 Problem
39 Problem
40 Problem
41 Problem : GATE 2003
42 Problem : GATE 2003
43 Problem : GATE 2004
44 Problem : GATE 2008
45 Problem : GATE 2016
46 Problem : GATE 2017
47 Problem : GATE 2020
48 Problem : GATE 2020
49 Problem : GATE 1993
Option (a) is Correct
50 Problem : GATE 1994
51 Problem : GATE 1996
Option (b) is Correct
52 Problem : GATE 1996
Option (b) is Correct
53 Problem : GATE 2003
Option (c) is Correct
54 Problem : GATE 2007
55 Problem : GATE 2007
Option (d) is Correct Option (a) is Correct 56 Problem : GATE 2013
Option (c) is Correct 57 Problem : GATE 2015
Option (a) is Correct 58 Thank you
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