Callibrate a Hall Probe: Planning

... Planning Exercise Design a laboratory experiment to calibrate an uncalibrated Hall probe and use it to investigate how the magnetic flux density mid-way between opposite poles of two permanent bar magnets varies with the separation of the bar magnets. Calibrating the Hall probe To calibrate the Hall probe, Helmholtz coils should be used as a uniform field is produced. Helmholtz coils1 The magnitude of the flux density2 in the region of uniform field is given by where B = flux density (T) ·0 = permeability of free space (4? x 10-7 Hm-1) n = no. of turns on coil I = current in each coil (A) R = radius of each coil (m) Formula 1 The magnitude of the Hall voltage3 measured by a Hall probe is given by where VH = Hall voltage (V) I = current in Hall probe (I) B = magnetic flux density (T) n = no. of electrons per unit volume (e/m3) e

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