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

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

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

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

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