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Unformatted text preview: 1 1 Magnetostatics (Chapter 7 & 8) Ampere’s Law Of Force and Biot-Savart Law • Magnetostatics is the branch of electromagnetics dealing with the effects of electric charges in steady motion (i.e, steady current or DC where d ρ /dt = 0). • In magnetostatics , the magnetic field is produced by steady currents . • A fundament al law of magnetostatics is Ampere’s law of force which is based on physical observation • Ampere’s law of force is analogous to Coulomb’s law in electrostatics. 2 • Ampere’s law of force is the “law of action” between current carrying circuits. • Ampere’s Force law gives the magnetic force between two current carrying circuits in an otherwise empty universe. I 1 I 2 Ampere’s Law of Force (Ch. 8) F 3 Experimental facts: – Two wires carrying current in the same direction attract. – Two wires carrying current in the opposite directions repel. – A short current carrying wire oriented perpendicular to a long current-carrying wire experiences no force. I 1 I 2 F 1 F 2 I 1 I 2 F 1 F 2 I 1 I 2 F 2 =0 – The magnitude of the force is inversely proportional to the distance squared. Ampere’s Law of Force 4 Magnetic Fields in analogy with Electric Fields Electric Field: – Distribution of charge creates an electric field E ( r ) in the surrounding space. – Field exerts a force F =q E ( r ) on a charge q at r Magnetic Field: – Moving charge or current creates a magnetic field H ( r ) in the surrounding space. – Field exerts a force F on a moving charge q at r – Emphasis this chapter (7) is on calculation of H – Emphasis in chapter 8 is on force law =>Unification of Electricity and Magnetism in Maxwell’s Equations. Elec 351 2 5 • The Biot-Savart law gives us the H-field arising at a specified point P from a given current distribution....
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This note was uploaded on 07/11/2011 for the course ELEC 251 taught by Professor Lynch during the Spring '10 term at Concordia Canada.
- Spring '10