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Physics, 26.10.2021 07:20 seawu

Compared to permanent magnets, why are electromagnets more useful in many modern technologies?
O A. In permanent magnets, the strength of the magnetic field is more
consistent.
O B. To use an electromagnet, a power supply is not necessary.
O C. Strong permanent magnets are too large to use.
O D. By controlling the current, electromagnets can be turned on and
off.

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