AC Characteristics
Multiple-choice exercise
1/5
1 What is the relationship between cycle time and frequency?
They are both measured in seconds.
They are directly proportional.
One value is the inverse of the other.
AC Characteristics
Multiple-choice exercise
2/5
2 What is the full-cycle average of a true ac waveform?
Zero
63.7% of the peak value
.
(2/p) × VP.
AC Characteristics
Multiple-choice exercise
3/5
3 Which piece of test equipment is used to measure peak-to-peak
voltage?
The oscilloscope
An ac voltmeter
A multimeter
AC Characteristics
Multiple-choice exercise
4/5
4 When are two sine waves considered to be out of phase?
When they have different frequencies.
When they have different amplitudes.
When they reach their peak values at different points in time.
AC Characteristics
Multiple-choice exercise
5/5
5 How many radians are in 90°?
57.3 radians
pi/2 radians
2pi radians
2. Phasors and Complex Numbers
Polar and Rectangular Notation
Multiple-choice exercise
1/4
1 Which of the following statements is true?
A scalar quantity has magnitude and direction.
A scalar quantity has magnitude and a phase angle.
A scalar quantity has magnitude and no phase angle.
Polar and Rectangular Notation
Multiple-choice exercise
2/4
2 What notation makes it easy to multiply vector quantities?
Coordinate notation
Rectangular notation
Polar notation
Polar and Rectangular Notation
Multiple-choice exercise
3/4
3 Which of the following statements about rectangular notation is true?
x-values and y-values can be positive or negative.
x-values can be positive or negative, but y-values must
always be positive.
x-values are always positive, but y-values can be positive or
negative.
Polar and Rectangular Notation
Multiple-choice exercise
4/4
4 What term is used to refer to a number written in the form x ± jy?
A complex number
A rectangular number
An imaginary number
3. The Concept of Impedance
RL Circuits
Multiple-choice exercise
1/3
1 What method is used to calculate the total circuit impedance for a
series RL circuit?
Add XL and R geometrically.
Add XL and R algebraically.
Add the rms values of XL and R.
RL Circuits
Multiple-choice exercise
2/3
2 If VS is used as the phase reference, what do we know about the current phase
angle in a series RL circuit?
The current phase angle is positive.
The current phase angle is always 0°.
The current phase angle is negative.
RL Circuits
Multiple-choice exercise
3/3
3 As frequency increases, what happens to IT in a parallel RL circuit?
IT increases and its phase angle becomes more negative.
IT decreases and its phase angle becomes less negative.
IT decreases and its phase angle becomes more positive.
RC Circuits
Multiple-choice exercise
1/4
1 Capacitive reactance is directly proportional to which of the
following?
Frequency
Neither. XC is inversely proportional to both.
Capacitance
2/4
2 A series RC circuit has a value of VS = 8 V - 45°. Which of the following is true?
XC = R
XC < R
XC > R
3/4
3 Assuming that VS is the phase reference, how does a decrease in operating
frequency affect the total current (IT) in a series RC circuit?
The magnitude increases and the phase angle becomes less negative
The magnitude decreases and the phase angle becomes less positive
The magnitude decreases and the phase angle becomes more positive
4/4
4 How does an increase in operating frequency affect the total current (IT) in a
parallel RC circuit?
The magnitude increases and the phase angle becomes more positive
The magnitude decreases and the phase angle becomes more positive
The magnitude increases and the phase angle becomes less negative
4. Resonance and Other Topics
RLC Circuits
Multiple-choice exercise
1/7
1 What is the phase relationship between VL and VC in a series CL
circuit?
VL leads VC by 90°.
VL and VC are 180° out of phase.
VL lags VC by 90°.
2/7
2 If VL < VC in a series CL circuit, which of the following is true?
VS is less than VC and has a negative phase angle.
VS is greater than VL and has a positive phase angle.
VS is greater than VL and has a negative phase angle.
3/7
3 If IL < IC in a parallel CL circuit, which of the following is true?
IT > IC and has a negative phase angle.
IT < IC and has a positive phase angle.
IT > IL and has a positive phase angle.
4/7
4 If XL > XC in a parallel CL circuit, which of the following is true?
IL > IC and the phase angle of IT is positive.
IL < IC and the phase angle of IT is negative.
IL< IC and the phase angle of IT is positive.
5/7
5 Which of the following is true for a series resonant LC circuit?
VS = VL - VC.
VS = VC - VL.
VS is dropped across the source's internal resistance
6/7
6 Which of the following is true for a parallel resonant LC circuit?
IT = 0 A and the phase angle is positive.
IT = 0 A and the phase angle is 0°.
IT = VS/RS and the phase angle is 0°.
7/7
7 A series RLC circuit is initially operated at its resonant frequency. What happens if
the operating frequency is increased?
The magnitude of IT decreases and its phase angle becomes more
negative.
The magnitude of IT decreases and its phase angle becomes more
positive.
The magnitude of IT increases and its phase angle becomes more
positive.