Problem 39
Conducting planes in air at \(z=0\) and \(z=d\) carry surface currents of \(\pm
K_{0} \mathbf{a}_{x} \mathrm{~A} / \mathrm{m} .(a)\) Find the energy stored in
the magnetic field per unit length \((0
Problem 40
A coaxial cable has conductor radii \(a\) and \(b\), where \(a
Problem 42
Find the mutual inductance between two filaments forming circular rings of radii \(a\) and \(\Delta a\), where \(\Delta a \ll a\). The field should be determined by approximate methods. The rings are coplanar and concentric.
Problem 44
Show that the external inductance per unit length of a two-wire transmission line carrying equal and opposite currents is approximately \((\mu / \pi) \ln (d / a)\) \(\mathrm{H} / \mathrm{m}\), where \(a\) is the radius of each wire and \(d\) is the center-to-center wire spacing. On what basis is the approximation valid?
