Magnetic field falls off as the inverse cube of axial distance for both a coil and a magnet¶

Claim · All claims
Evidence · 1 study · design r2 · q2
Currency · newest study 2014 · not yet checked against its sources · not reviewed by a person

Subclaims¶

q2 i? Data fits of B(z) = a z^b return exponents consistent with the expected z−3 dependence for both the coil and the magnet. → V.O.M. Lara 2014

Evidence¶

V.O.M. Lara 2014¶

V.O.M. Lara, D. F. Amaral, D. Faria, and L. P. Vieira. (2014). Demonstrations of magnetic phenomena: Measuring the air permeablity using tablets. https://arxiv.org/abs/1405.6581 doi:10.48550/arxiv.1405.6581

q2 · i? · the article prints no effect size for this finding · design · r2

Second demonstration-set experiment: the coil (current up to I∼ 0.9A) and the magnet were moved by equal displacements and B recorded at each distance; Table I fits give b = −3.05112± 0.03917 (coil) and b = −3.09232± 0.01217 (magnet), showing "excellent agreement with the expected z−3 dependence".

"In addition, we perform a data fit usingB (z) =azb, as shown in table I. For both cases we obtain an excellent agreement with the expected z−3 dependence [9]."

Discussion¶

Related Claims¶

• The magnet data cannot determine air permeability; only the magnet's dipole moment can be estimated — related
• Magnetic field measured by a tablet magnetometer depends linearly on the coil current — related
• The demonstration set yields a fair estimate of air permeability µair from coil data — a narrower finding that bears on this claim