Ampere's Law

What is the equation for Ampère’s Law?

∮B⋅dl=μ0​Ienc​

What shape is the magnetic field around a long, straight current-carrying wire?

Circular, centered around the wire (direction determined by right-hand rule)

Magnetic field outside a long straight wire is given by:

B=μ0​I​/2πr

Magnetic field inside a cylindrical conductor with uniform current:

B=μ0​Ir/2πr²

What’s the magnetic field between two conductors in a coaxial cable?

B=μ0​I​/2πr

What is the magnetic field outside a coaxial cable if both conductors carry equal and opposite currents?

B=0

Magnetic field inside an ideal solenoid:

B=μ0​nI, where n=N/L, the number of turns per unit length

What does Ienc​ mean in Ampère’s Law?

The net current enclosed by the Amperian loop.

What is the unit of magnetic field B?

T

What’s the right-hand rule for magnetic field around a wire?

Thumb points in direction of current, curled fingers show direction of magnetic field lines