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

the core is permitted to move freely within the coil
changing the polarity of the current in the coil changes the polarity of the magnetic field around the core
None of these
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

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Electronic Principles
Which one of the following statements is true for resistance in a parallel circuit?

The total resistance of a parallel circuit is equal to the total voltage
The total resistance of a parallel circuit is always less than the value of the smallest resistance
None of these
The total resistance in a parallel circuit is equal to the average value of the individual resistances
The total resistance is equal to the sum of the individual resistances in a parallel circuit.

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Electronic Principles
Which one of the following is a direct statement of Ohm's law?

The algebraic sum of voltages in a loop is equal to zero
The voltage drop across a resistance is proportional to the value of resistance and the amount of current flowing through it
The total resistance of a parallel circuit is less than the value of the smallest resistance
None of these
The algebraic sum of currents entering and leaving a point is equal to zero

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Electronic Principles
In a pure inductor:

ac current leads the voltage by 90 degree
ac current lags the voltage by 90 degree
None of these
ac current is converted to dc voltage
ac current and voltage are exactly in phase

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