These methods are based on the use of externally-applied magnetic fields from permanent magnets or from electromagnet coils driven by either alternating or direct current.
(These methods; are based; on the use of externally-applied magnetic fields from permanent magnets or from electromagnet coils) (electromagnet coils; driven; by either alternating or direct current)
These methods electromagnet coils
are based driven
on the use of externally-applied magnetic fields from permanent magnets or from electromagnet coils
by either alternating or direct current