Question

If a magnet is carefully broken in half along its long axis, as shown in Fig. how would the magnetic strength of each piece compare with that of the original magnet?

• A. 1 : 1
• B. 2 : 1
• C. 1 : 2
• D. 1 : 4

Answer 1

Answer: (C)

1 : 2

The surface field strength of a magnet is only a function of its shape, not its size. Long thin magnets with poles at each end have a very intense magnetic field at each pole, more so than a short fat magnet, but only over a small area. They do have good reach though, we still have significant, although not terribly strong field at about one length, much more than a shorter magnet of the same diameter.
The distance that the magnet casts a magnetic field gets smaller as the magnet gets smaller. So the half-size magnet would have a half-sized magnetic field strength at a distance. The ratio of the magnetic strength of smaller magnet to the original size magnet is given as 1:2.
A magnet could cause a measurable decrease in strength; but it would depend on the material. For example,neodymium magnets probably not very much at all, may not be measurable, whereas ferrites it could be quite a lot.