Question

4.3.2 test (cst): electromagnets
question 2 of 20
which device contains at least one permanent magnet?
a. an electromagnet
b. an electric lamp
c. a steel nail
d. a magnetic jewelry clasp

Explanation:

• An electromagnet is a magnet in which the magnetic field is produced by an electric current. It does not contain a permanent magnet.
• An electric lamp works on the principle of heating of a filament (in incandescent lamps) or gas discharge (in fluorescent lamps etc.). It has no permanent magnet.
• A steel nail can be magnetized but is not a device with a permanent magnet.
• A magnetic jewelry clasp uses a permanent magnet to hold the two parts of the clasp together.

Answer:

D. A magnetic jewelry clasp