Force on current carrying wire in a magnetic field #2 (NCPQ)

Описание: This video is a demonstration of the force on a current carrying wire in a magnetic field (NCPQ U3&4 Expt 7.4). In this demonstration, a strong magnetic field is produced using two 10 mm x 5 mm rare earth disc magnets of surface field strength 0.4667 T (4667 G) held 10 mm apart by a small piece of aluminium channel. A stiff copper wire is held rigidly between the poles of the magnets using a clamp and retort stand. An electric current is passed through the wire and the downwards force on the magnets and channel is shown by a scale reading on the balance in grams. The effective length of the wire in the magnetic field is 10 mm.

A series of trials is undertaken with the current being increased from 0.40 A to 1.00 A and the scale reading (converted to Newton, N) goes from 0.0013 N to 0.0033 N. If you pause the video you can get pairs of values of your own. When plotted with current on the horizontal axis and force on the vertical axis, we get a gradient (F/I) equal to 0.0033 N/A. Rearranging the formula F = BIL to B = F/(I L) we substitute 0.010 m for the length (L) and this gives a value for B of 0.33 T. The accepted value for B = 0.4667 T so that means there is a percentage error (E%) = 36%. This seems high but it is reasonable given the limitations of the measuring equipment and the design of the experiment.

Filmed by Dr Richard Walding at Moreton Bay College in November 2018 with the assistance of my very talented student Kayleigh who skipped Chapel to help me.

Reference: New Century Physics for Queensland - Units 3 & 4, 3rd edition, OUP, 2019 by Richard Walding. Chapter 7.4 page 195-200

Web: seniorphysics.com/ncpq