# Shared Flashcard Set

## Details

Electrical Theory Questions
Questions for upcoming electrical test.
20
Engineering
Professional
02/13/2008

Term
 What is the equation for inductive reactance?XL
Definition
 XL = 2pfL
Term
 What is the equation for capacitive reactance?
Definition
 1/(2pfC)
Term
 Describe the relationship between voltage and current in an inductuve circuit.
Definition
 Voltage leads current by 90 degrees in an inductive circuit.(ELI the ICE-man)
Term
 What is the equation for impedance in and R-L circuit.
Definition
 Z=√(R2+XL2)
Term
 What is the equation for resonance frequency?(Fres)
Definition
 Fres=1/(2π(√(LC))
Term
 What is the equation for impedance in a series R-C-L circuit?
Definition
 Z = √[R2+(Xc+XL)2]
Term
 What is the equation for impedance for a parallel R-C-L circuit?
Definition
 ZT=VT/ITIT=√(IR2+(IL-IC)2)
Term
 Given a parallel R-C-L circuit at resonance, DESCRIBE the net reactance of the circuit.
Definition
 Net Reactance (X) is at zero and the series resistance of the circuit determines circuit current output.
Term
 Describe the characteristics of inductors when they are placed in and AC circuit.
Definition
 Because of a constantly changing current, a constantly changing EMF is produced. Becuase this EMF flows in a direction opposite the normal current it is measured in ohms.The value of the self induced EMF varies as a sine wave and lags the current by 900.
Term
 19. Given a parallel R-C-L circuit at resonance, DESCRIBE the circuit output relative to current.
Definition
 Net Reactance (X) is at MAXIMUM and circuit current output is minimum.
Term
 Given an AC single-phase or three-phase circuit, describe the characteristics of the power generated in the circuit.
Definition
 AC power components are not in phase and as a result not all power can be used to perform work. Reactive power must be considered and removes some of the apparent power. The remaining power is true power and is the only component that may be used in real work.
Term
 Describe the relationship between apparent, true (real), and reactive power using a power triangle.
Definition
 Apparent power (generator output) is the hypotenuses. True power (WATTS) is adjacent to the hypotenuse and forms angle θ. Reactive power (VARS) is the opposite angle from
Term
Definition
 Power factor associated with capacitive circuits(ice man in eli the ice man)
Term
 Define lagging power factor.
Definition
 Power factor associated with inductive circuits
Term
 State the reason three phase systems are used in the industry.
Definition
 Three-phase circuits weigh less than single-phase circuits of the same power rating.They have a wide range of voltages and can be used for single-phase loads.Three-phase equipment is smaller in size, weighs less, and is more efficient than single-phase equipment.
Term
 What is the equation for true power?
Definition
 P = I2R = EI cos
Term
 What is the equation for reactive power?
Definition
 Q= I2X = EI sinq
Term
 What is the equation for apparant power?
Definition
 S = I2Z = ITE
Term
 What is the equation for power factor?
Definition
 Cos θ
Term
 State the indications of an unbalanced load in a three-phase power system
Definition
 Unbalanced three-phase circuits are indicated by abnormally high currents in one or more of the phases
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