Figure 3-2. Horseshoe Magnet with Poles Close Together.
Figure 3-3. Horseshoe Magnet Fused into a Ring.
A transverse crack in the fused magnet or circularly magnetized part (see Figure 3-4) will create a leakage field with
north and south poles on either side of the crack. Some of the magnetic flux (lines of force) will exit the metal and
form a leakage field. Magnetic materials or particles will be attracted by the leakage field created by the crack, forming
an indication of the discontinuity in the metal part. This is the principle whereby magnetic particle indications are
Figure 3-4. Crack in Fused Horseshoe Magnet.