Electronic Principles
Which one of the following phrases best describes residual magnetism?

Magnetism that remains in the core of an electromagnet after the current through the coil is turned off
None of these
The force of attraction between the poles of a permanent and temporary magnetic field
The amount of magnetic flux that is not confined to the core material of an electromagnet
The circular magnetic field that surrounds a conductor carrying a current

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Electronic Principles
Which one of the following statements most accurately reflects the nature of ac power?

The current in an ac circuit flows in two directions at the same time
The current in an ac circuit flows in one direction, but changes value periodically
The current in an ac circuit flows in one direction at a steady level
None of these
The current in an ac circuit changes direction periodically

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