Figure 3

(a) Sketch of the experimental setup; a circular U -shaped conductor (orange, with R e = 65 mm ) moves with rotation frequency ν around the z axis (arrows indicate the positive rotation direction). Two coils (in red), whose axes are radially aligned, are used to measure the magnetic coupling between them. (b) Numerical calculations for an oscillating magnetic dipole [in white, for ω 0 / ( 2 π ) = 9 Hz ]. Colors correspond to the real part of the normalized radial field, B ρ / B 0 [where B 0 ≡ μ 0 m / ( 2 π z 0 3 ) with z 0 = 5 mm] for different rotation frequencies of the conductor, ν = − 30 , 0, 11.7, and 36.7 Hz (from left to right). Plots show the magnetic field distribution evaluated at the plane of the dipole. White dots indicate positions where measurements were taken. (c) Out-of-phase component of the voltage measured in the receiving coil (symbols) as a function of the velocity of the conductor [for a signal frequency of ω 0 / ( 2 π ) = 9 Hz ]. Measurements were taken at three different distances from the source coil, r 1 = 11.4 mm (pink), r 2 = 13.1 mm (yellow), and r 3 = 15.5 mm (purple), see inset. For each distance, measurements are normalized to the voltage induced at the receiving coil in free space, | V 0 | . Solid lines are the corresponding numerical calculations considering point dipoles. Shadow areas are defined by considering uncertainties in the experimental parameters used for the numerical calculations [18]. Dashed vertical lines indicate the frequencies of the numerical calculations in (b). Error bars ( 1 σ ) are shown for the three cases; most of them are symbol size or smaller.