Why do many devices using electromagnets also need a permanent magnet?

A.
because the devices need a second magnetic field to hold the electromagnet in place

B.
because electromagnets do not work when there is current going through the circuit

C.
because electromagnets can only repel magnetic materials and cannot attract them

D.
because the devices use the interaction of two magnetic fields to create motion

1 answer

D. because the devices use the interaction of two magnetic fields to create motion
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