PASCO EM-8642A Magnetic Force Accessory - Manual (Page 7)

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About the Equipment
Variable Gap Magnet
The Variable Gap Magnet consists of two one inch (2.54 centimeter) diameter neodymium magnets on an iron
base with adjustable magnet holders. Two flat iron pole pieces are included to provide a uniform magnetic field
when needed. The gap between the faces of the two magnets can be varied from 0.5 cm to 8.9 cm by turning the
adjustment screws. The base has a threaded hole for mounting on a 12.7 mm diameter threaded support rod (1/2”
diameter by 13 thread) such as the PASCO ME-8988 25-cm Stainless Steel Threaded Rod. The base can be
mounted on a non-threaded support rod that is less than 12.7 mm (1/2”) in diameter using the thumbscrew on the
side of the base.
The approximate magnetic field strength without the pole pieces in place is shown in Table 1.1. Note that the mag-
netic field strength may vary from magnet to magnet. (These sample measurements were taken with a Model 4048
F.W. Bell Gauss/Tesla Meter.)
The magnetic field is intense between the magnet faces, but drops off to about 30 gauss at the outside edges of the
magnets. Nevertheless, do not put the magnets close to magnetic media, computer hard disks, monitors, or other
items that would be harmed by an intense magnetic field.
Pole Pieces
The flat iron pole pieces are 7.95 cm long
(3.125“) by 4.44 cm wide (1.75”) by 0.5 cm
thick (0.19”). When the pole pieces are
placed on the magnet faces, the magnetic
field between the pole pieces is relatively
uniform except at the edges of the pole
pieces. With a separation of 1 cm (0.4 in)
between the pole pieces, the magnetic field
varies between 8500 and 9000 gauss.
Be careful when handling the pole pieces
near the magnets. Use the adjustment
screws to separate the two magnets. Slide
the pole piece onto the magnet from the
edge of the magnet. Center each pole piece
on the magnet face.
Try to prevent the pole pieces from strik-
ing hard against the neodymium magnets
because the impact may break or chip
the magnets.
Table 1.1:
Gap (cm) Magnetic Field at Poles
(tesla/gauss)
Magnetic Field between Poles
(tesla/gauss)
0.5 1.02 T / 10200 G 1.00 T / 10000 G
0.6 1.00 T / 10000 G 0.95 T / 9500 G
1.0 0.85 T / 8500 G 0.75 T / 7500 G
8.9 0.55 T / 5500 G 0.35 T / 3500 G
Figure: Magnet with Pole Pieces
Pole Pieces
Thumbscrew
Center the pole
piece on the
magnet.