Katie assembled a magnet tester out of cardboard, pencils, and magnets. Metal paper clips easily stuck to the bottom piece of cardboard. But when she inserted a steel knife, most of the paper clips fell off as shown in the image below.

Question

Which of the following best describes why the magnet could no longer hold the paper clips once the steel knife was inserted?
A.
The magnetic field increased when the steel knife was inserted.
B.
Gravity increased when the steel knife was brought close to the magnets.
C.
The magnetic field was blocked when the steel knife was inserted.
D.
Gravity was blocked when the steel knife was brought close to the magnets.

Answer 1

The best explanation for why the magnet could no longer hold the paper clips once the steel knife was inserted is:

C. The magnetic field was blocked when the steel knife was inserted.

In this case, the steel knife, being a magnetic material, likely disrupted the magnetic field created by the magnets and diminished their ability to attract the paper clips effectively.