Biot-Savart Law: B field from a current Refer p. 689 for straight wire Right hand rule for direction i=100 A, R=10 m B=210-6 T = 210-2 Oe (earth field) Again superposition principle is still valid

Example: Rail Gun Acceleration: 5  106 g Final speed: 1 km/s Duration: 1 ms

Ampere’s Law Gauss’ law Ampere’s Law Quantitative relationship between electric field (direction and magnitude) on a CLOSED SURFACE (Gaussian surface) and total charges inside the Gaussian surface. Quantitative relationship between magnetic field (direction and magnitude) on a CLOSED LOOP (Amperian Loop) and total current passing through the Amperian loop.

Ampere’s Law: Continues Define dS 2. Assign sign to current using RH rule fingers  Amperian loop (dS) direction of outstretched thumb  +i opposite  -i