Lecture_12_(Chap.18)

# Lecture_12_(Chap.18) - Magnetic Dipole Moment 0 2R 2 I far...

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Magnetic Dipole Moment r from coil: 2 0 2 I R p 2 1 r from dipole: far from coil: 3 4 z B z sq p z E z 3 0 4  far from dipole: B z 3 0 2 AI I R z 2 4 magnetic dipole moment: - vector in the direction of B 1

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Magnetic Monopoles An electric dipole consists of two opposite charges – monopoles Break magnet: N S S N There are no magnetic monopoles! 2
Twisting of a Magnetic Dipole The magnetic dipole moment acts like a compass needle! In the presence of external magnetic field a current-carrying loop rotates to align the magnetic dipole moment along the field B . 3

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A Coil of Wire What if we had a coil of wire? 0 2 R 2 I single loop: B z 4 R 2 z 2 3/2 B 0 2 R 2 NI or rns: z 4 R 2 z 2 For N turns: 4
Magnetic Field of a Solenoid Step 1: Cut up the distribution into pieces rigin: nter of the solenoid Step 2: Contribution of one piece origin: center of the solenoid B z 0 4 2 R 2 I 2 2 3/2 one loop: B R d z Number of loops per meter: N/L Number of loops in z : ( N/L ) z ield due to 0 2 R 2 I N Field due to z : B z 4 R 2 d z 2 L z 5

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Magnetic Field of a Solenoid Step 3: Add up the contribution of all the pieces dB z 0 4 2 R 2 I 2 2 3/2 N L dz R d z 0 2 R 2 NI dz L /2 B B z 4 L R 2 d z 2 L 2 NI d L d L Magnetic field of a solenoid: B z 0 4 L d L  2 R 2 d L 2 R 2 6
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## This note was uploaded on 04/23/2011 for the course PHYS 272h taught by Professor Staff during the Spring '08 term at Purdue.

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Lecture_12_(Chap.18) - Magnetic Dipole Moment 0 2R 2 I far...

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