Electronic Principles
The core of an electromagnet is said to be in saturation when:

frequent changes in the direction of current through the coil causes heating effects in the core material
changing the polarity of the current in the coil changes the polarity of the magnetic field around the core
the core is permitted to move freely within the coil
an increase in current through the coil causes no further increase in the mmf
None of these

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Electronic Principles
When a parallel RLC circuit is operating at its resonant frequency:

inductive reactance is equal to the capacitive reactance
inductive reactance is greater than the capacitive reactance
the difference between inductive and capacitive reactance is equal to the resistance
capacitive reactance is greater than the inductive reactance
None of these

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Electronic Principles
The total impedance of a parallel RLC circuit:

is equal to the sum of the values of resistance, inductive reactance and capacitive reactance
is maximum at the resonant frequency
None of these
always decreases as the applied frequency increases
always increases as the applied frequency increases

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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 one direction at a steady level
None of these
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 changes direction periodically

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