AC CIRCUITS Flashcards
Current that continually reverses its direction
A. Direct current
B. Alternating current
C. Pulsating direct current
D. Pulsating alternating current
Alternating current
Which of the following effects are generally less for an alternating current than for a direct current?
A. heating effects
B. chemical effects
C. magnetic effects
D. impedance
chemical effects
When the sole purpose of ac is to produce heat, the selection of conductor is based on _______ value of the current.
A. Average
B. peak
C. RMS
D. Peak
RMS
Root-mean-square is also called the ________ voltage.
A. average
B. peak
C. effective
D. maximum
effective
The net reactance in a series RLC circuit is
A. XL
B. XC
C. XC + XL
D. XL - XC
XL - XC
For an RL circuit, the power factor cannot be less than _____ and greater than ______.
A. 0, 1
B. 1, 0
C. 0, -1
D. -1, 0
0, 1
When the voltage remains the same, the current will ________ as the impedance decreases.
I. decrease II. increase
A. I only
B. Both
C. Either I or II
D. II only
II only
The resistance in a series RC circuit is increased, the magnitude of the phase angle
A. increases
B. remains the same
C. decreases
D. changes indeterminately
decreases
Which of the following AC device is used to measure the angle between the voltage and its current?
A. reactive meter
B. power factor meter
C. demand meter
D. phase angle meter
phase angle meter
The power factor of an inductive circuit can be best improved by connecting a capacitor/s to it in ___________
A. either
B. both
C. series
D. parallel
parallel
In a series RLC circuit, the current at resonance is ________.
A. Zero
B. infinity
C. minimum
D. maximum
maximum
In a series RLC circuit, the impedance at resonance is ________.
A. zero
B. infinity
C. minimum
D. maximum
minimum
The current flowing in L and C at parallel resonance are
A. zero
B. equal
C. infinite
D. different
Equal
Power in a three phase delta system with balanced load is equal to
A. √3 x VL x IL x power factor
B. √3 x Vph x Iph x power factor
C. 3 x Vph x IL x power factor
D. 3 x VL x IL x power factor
√3 x VL x IL x power factor
For an unbalanced load which connection is suitable?
A. 3-wire open delta
B. 4-wire wye connection
C. 3-wire delta connection
D. 3-wire wye connection
4-wire wye connection
Circuit breakers are rated based on their _________ fault.
A. unsymmetrical
B. symmetrical
C. both
D. None of these
symmetrical
In two-wattmeter method, the reading of one of the wattmeters will be zero when
A. load in one of the phases is zero
B. power factor is unity
C. power factor is 0.5
D. neutral is earthed
power factor is 0.5
The readings of the wattmeter will be the same in the two-wattmeter method when ________.
A. load in one phases is zero
B. power factor is 0.50
C. power factor is unity
D. neutral is grounded
power factor is unity
When the current and voltage are out of phase by 90 degrees, the power is
A. average
B. zero
C. maximum
D. minimum
zero
The value of form factor for pure sine wave is
A. 1.414
B. 0.707
C. 0.637
D. 1.11
1.11
