  A spilt-ring resonator experiment suitable for senior physics undergraduates
is described and demonstrated in detail. The apparatus consists of a conducting
hollow cylinder with a narrow slit along its length and can be accurately
modelled as a series $LRC$ circuit. The resonance frequency and quality factor
of the split-ring resonator are measured when the apparatus is suspended in
air, submerged in water, and submerged in an aqueous solution of various
concentrations of NaCl. The experimental results are used to extract the
dielectric constant of water and to investigate the dependence of the resonator
quality factor on the conductivity of the NaCl solution. The apparatus provides
opportunities to experimentally examine radiative losses, complex permittivity,
the electromagnetic skin depth, and cutoff frequencies of rf propagation in
cylindrical waveguides, which are all concepts introduced in an undergraduate
course in electrodynamics. To connect with current research, the use of
split-ring resonators as a tool to precisely measure the electromagnetic
properties of materials is emphasized
