State Ampere's law for steady currents.

What kind of path is used in the line integral in Ampere's law?

What does \(I_{\mathrm{enc}}\) mean in Ampere's law?

A closed loop encloses \(4.0\,\mathrm A\) of current in the positive sense. Find \(\oint\vec B\cdot d\vec l\).

A circular Amperian loop has radius \(0.20\,\mathrm m\) and encloses a long straight wire carrying \(5.0\,\mathrm A\). Use Ampere's law to find \(B\) on the loop.

An Amperian loop encloses currents \(6.0\,\mathrm A\) and \(2.0\,\mathrm A\) in the positive sense, and \(3.0\,\mathrm A\) in the negative sense. Find \(I_{\mathrm{enc}}\).

Why can \(\oint\vec B\cdot d\vec l\) become \(B(2\pi r)\) for a long straight wire?

Ampere's law is always true for steady currents. Why might it still be unhelpful for finding \(B\) around a short bent wire?

Check the units of Ampere's law by showing that \(\mu_0I\) has units of \(\mathrm{T\,m}\).

A loop direction is chosen counterclockwise as viewed by you. A current passes through the loop toward you. Is its contribution to \(I_{\mathrm{enc}}\) positive or negative?