Electronic Principles
A transformer has a primary voltage of 120 V rms and a secondary voltage of 25 V rms. If the secondary current is 1A rms, what is the primary current?

7.8 mA
208 mA
300 mA
None of these
200 mA

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

None of these
Magnetism that remains in the core of an electromagnet after the current through the coil is turned off
The circular magnetic field that surrounds a conductor carrying a current
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

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

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Electronic Principles
Which one of the following statements is true for the impedance of a series RC circuit?

None of these
The impedance is greater than either the resistance or capacitive reactance but less than their sum
The impedance is greater than the sum of the resistance and capacitive reactance
The impedance is less than the sum of the resistance and capacitive reactance
The impedance is equal to the sum of the resistance and capacitive reactance

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