Biot-Savart Law: B field from a current

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Biot-Savart Law B field from a current
Refer p. 689 for straight wire
Right hand rule for direction
i100 A, R10 m
B2?10-6 T 2?10-2 Oe (earth field)
Again superposition principle is still valid
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Example Rail Gun
Acceleration 5 ? 106 g Final speed 1
km/s Duration 1 ms
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Amperes Law
Gauss law
Amperes 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.
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Amperes Law Continues

1. Define dS

2. Assign sign to current using RH rule

• fingers ? Amperian loop (dS)

• direction of outstretched thumb ? i
• opposite ? -i