Deck 20: Time Response of Reactive Circuits

Question 1

When there is a sudden change in voltage, a capacitor, for an instant, appears as:

A) a resistive circuit
B) a short circuit
C) a fully charged capacitor
D) an open circuit

Answer 1

a short circuit

Question 2

The output of an RC integrator approaches the shape of the input pulse when:

A) the pulse width is increased
B) the pulse width is decreased
C) the pulse is at minimum
D) the pulse is at maximum

Answer 2

the pulse width is increased

Question 3

The RC differentiator is:

A) a basic high-pass filter
B) a basic band-pass filter
C) a basic low-pass filter
D) a basic band-stop filter

Answer 3

a basic high-pass filter

Question 4

The rate of charging and discharging of a capacitor is controlled by:

A) the period of the input
B) the peak input voltage
C) the RC time constant
D) the frequency of the input

Question 5

If the resistor voltage in a differentiating circuit is down to + 2.4 V at the end of a 14 V input pulse, to what negative value will the resistor voltage go in response to the falling edge of the input?

A) -11.6 V
B) -16.4 V
C) -14 V
D) -2.4 V

Question 6

What is the capacitor voltage in an RC integrator when the pulse width is equal to or greater than five time constants?

A) fully charged
B) 37% of maximum
C) 63% of maximum
D) 86% of maximum

Question 7

In an R-C integrating circuit, the output voltage is taken across the capacitor.

Question 8

The shape of a repetitive-pulse affects the determination of the pulse repetition frequency.

Question 9

If a periodic pulse waveform is applied to an RC integrator, the output waveshape depends on the relationship of the circuit time constant and the duty cycle of the input pulses.

Question 10

The rising and falling edges of a pulse waveform contain the higher frequency components.

Question 11

If R = 2.2 kΩ, C = 1 µF, the pulse width = 5 ms, and the peak voltage of the pulse = 50 V, to what voltage will the capacitor charge in an RC integrator?

A) 22.43 V
B) 44.85 V
C) 18.57 V
D) 37.41 V

Question 12

The time for a capacitor to fully charge or discharge is called the transient ramp.

Question 13

The flat portion of a pulse waveform contains the average value.

Question 14

In an R-L differentiating circuit, the output voltage is taken across the resistor.

Question 15

The rise time of an ideal pulse is zero.

Question 16

When the pulse width is less than five time constants, the capacitor voltage in an RC integrator:

A) only partially charges
B) follows the input voltage
C) charges to maximum
D) discharges to minimum

Question 17

The voltage across a capacitor in an RC integrator circuit cannot change exponentially, it can change only instantaneously.

Question 18

Integration is:

A) an averaging process
B) a process for establishing a rate of change
C) used for mixing different input signals
D) a summing operation

Question 19

The transient time of an R-C or R-L circuit equals five time constants.

Question 20

With repetitive pulses, the amount of capacitor charge or discharge in an RC integrator depends upon:

A) the circuit time constant
B) the input peak voltage
C) the input frequency
D) both the circuit time constant and the input frequency

Question 21

In a repetitive-pulse RC integrator circuit, what would the steady-state voltage equal at the end of the fifth pulse? Assume a VIN of 20 V.

A) 0 V
B) 14.62 V
C) 1.46 V
D) 20 V

Question 22

A series of pulses is called:

A) periodic
B) rise time
C) pulse width
D) duty cycle

Question 23

An) will decrease the time constant in an RC integrator or differentiator.

A) open resistor
B) shorted resistor
C) leaky capacitor
D) shorted capacitor

Question 24

For a capacitor to completely charge in an RC integrator, the pulse width must be _ five time constants.

A) less than
B) much less than
C) greater than or equal to
D) much greater than

Question 25

If the capacitor in an RC integrator shorts, the output:

A) would measure zero volts
B) is at ground
C) would measure the same as the input
D) none of the above

Question 26

Figure 20-1
A certain pulse waveform has a rise-time 6 nS and a fall-time of 9 nS. What is the highest frequency component in the waveform?

A) 117 MHz
B) 58.3 MHz
C) 23.3 MHz
D) 38.9 MHz

Question 27

Figure 20-3
See Figure 20-3. What is the peak current that flows through the capacitor?

A) 0 mA
B) 10 mA
C) 1 mA
D) 5 mA

Question 28

Figure 20-1
What is the steady state output of the differentiator circuit in Figure 20-1?

A) 20 V
B) 6.37 V
C) 12.74 V
D) 0 V

Question 29

The top or flat portion of a pulse represents:

A) the peak value
B) the higher frequency components
C) the average value
D) the lower frequency components

Question 30

Figure 20-2
See Figure 20-2. Assume that the capacitor is initially charged to 3 V before the switch is closed. What is the peak current IC that flows after the switch is closed?

A) 0.7 mA
B) infinity
C) 0.3 mA
D) 1.0 mA

Question 31

Figure 20-3
See Figure 20-3. What is VC at t = 1 ms? Assume that the capacitor is initially discharged.

A) VC = 8.33 V
B) VC = 0 V
C) VC = 5 V
D) VC = 10 V

Question 32

A mathematical operation for finding the area under the curve of a graph is called .

A) integration
B) mixing
C) curve averaging
D) differentiation

Question 33

Figure 20-2
See Figure 20-2. Assume that the capacitor is initially charged to 3 V before the switch is closed. What is the current that flows after an elapsed time of 20 ms?

A) 0.67 mA
B) 0.20 mA
C) 0.23 mA
D) 0.47 mA

Question 34

What is the highest frequency contained in a pulse that has rise and fall times of 17 ns?

A) 20.6 MHz
B) 10.3 MHz
C) 168 MHz
D) 206 MHz

Question 35

A mathematical operation that determines the rate of change of a curve is called .

A) mixing
B) integrator
C) curve averaging
D) differentiation

Question 36

What does the average value of the differentiator output voltage equal during steady state?

A) peak value
B) 0 V
C) 0.637 × Peak
D) 0.707 × Peak

Question 37

The average value of a waveform is its:

A) ac component
B) dc component
C) tw
D) rising edge minus falling edge

Question 38

The fast rising and falling edges of a pulse waveform represent:

A) the rise times
B) the lower frequency components
C) the fall times
D) the higher frequency components

Question 39

The RC differentiator is characterized by:

A) introduces tilt to the flat portion of a pulse
B) eliminates the dc component of the input
C) produces a zero average-value output voltage
D) reduction of lower frequency components
E) all of the above

Question 40

An RL integrator can act as a _ filter and an RC differentiator can act as a filter.

A) high-pass, low-pass
B) low-pass, high-pass
C) high-pass, high-pass
D) low-pass, low-pass

Question 41

Figure 20-3
See Figure 20-3. If the square wave pulse width is decreased to 1.0 µs, how will the VC waveform change?

A) The average value will drop to zero
B) The peak voltage reached will increase.
C) The corners will be less rounded
D) The waveform will become flattened.