AC Fundamentals, Circuit and Circuit Theory
The effective resistance of an iron-cored choke working on ordinary supply frequency is more than its true resistance because of

Capacitive effect between adjacent coil turns
Increase in temperature
Iron loss in core
Skin effect

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AC Fundamentals, Circuit and Circuit Theory
A phasor is

A colored tag or band for distinction between different phases of a 3-phase supply
An instrument used for measuring phases of an unbalanced 3-phase load
A line which represents the magnitude and phase of an alternating quantity
A line representing the magnitude and direction of an alternating quantity

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AC Fundamentals, Circuit and Circuit Theory
The series and parallel resonance on L-C circuit' differs in that

Series resonance needs a high-resistance source for sharp increase in current
Series resistance needs a low-resistance source for sharp rise in current
Parallel resonance needs a low-resistance source for a sharp increase in impedance
Parallel resonance needs a low-resistance source for a sharp rise in line current

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AC Fundamentals, Circuit and Circuit Theory
Time constant of a capacitive circuit

Increases with the decrease of capacitance and decrease of resistance
Increase with increase of capacitance and increase of resistance
Increases with the increase of capacitance and decrease of resistance
Increases with the decrease of capacitance and increase of resistance

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