Deck 23: RC and LR Time Constants

Question 1

Whether an RC time constant is long or short depends on the ______________ width of the applied voltage.

Answer 1

pulse

Question 2

The voltage across R in an RC circuit is called a ______________ output because v_R can change instantaneously.

Answer 2

differentiated

Question 3

An RC ______________ can also be described as a circuit whose output is proportional to the charge being stored.

Answer 3

integrator

Question 4

X_C and the R_C time constant are both measures of the reaction of C to a change in _______________.

Question 5

A coupling capacitor must exhibit capacitive reactance that is one-tenth or ______________ of its series resistance at the desired frequency.

Question 6

In electronic circuits, the time constant is useful in analyzing the effect of L or C on the waveshape of ______________ voltages.

Question 7

RC circuits are more common than RL circuits because capacitors are _____________.

Question 8

______________ response is a temporary condition that exists only until the steady-state current is reached.

Question 9

More series resistance makes the L/R time constant ______________.

Question 10

RC specifies the time it takes C to charge to ______________ percent of the charging voltage.

Question 11

The average height of any waveform over one full cycle is its

A) dc value
B) ac value
C) peak value
D) effective value

Question 12

Whether an RC time constant is long or short depends on the

A) capacitance only
B) resistance only
C) impedance
D) pulse width of the applied voltage

Question 13

The voltage across R in an RC circuit is called a(n)

A) integrated output
B) differentiated output
C) passive output
D) reactive output

Question 14

The voltage across C in an RC circuit is called a(n)

A) integrated output
B) differentiated output
C) passive output
D) reactive output

Question 15

A circuit whose output is proportional to the charge being stored is a(n)

A) RC integrator
B) RC differentiator
C) LC notch filter
D) LC differentiator

Question 16

What is the time constant for an RC circuit that has an R of 10 k? and C of 0.05 ?F?

A) 0.5 s
B) 0.5 ms
C) 5.0 ms
D) 5.0 s

Question 17

A coupling capacitor must be

A) one-tenth or less of its series R at the desired frequency
B) ten times or greater than its series R at the desired frequency
C) dielectric

Question 18

The voltage across any inductance, v_L is equal to

A) L(di/dt)
B) X_L(di/dt)
C) L/(di/dt)
D) X_L/(di/dt)

Question 19

In electronic circuits, when analyzing the effect of L or C on the waveshape of nonsinusoidal voltages, what is useful?

A) Ohm's law
B) Coefficient of coupling
C) Time constants
D) Pythagorean's theorem

Question 20

RC circuits are more common than RL circuits because

A) capacitors are more economical
B) capacitors are larger
C) capacitors have strong magnetic fields
D) capacitors cost more to manufacture

Question 21

With nonsinusoidal voltage and current, the effect of L or C is to produce

A) a change in waveshape
B) out of phase voltages or currents
C) LC filters
D) oscillator circuits

Question 22

The time constant is what percentage of change in current through L or the voltage across C?

A) 36.8%
B) 63.2%
C) 70.7%
D) 29.3%

Question 23

A resistance

A) increases opposition with an increase in frequency
B) has only opposition to current
C) has a concentrated magnetic field that opposes a change in current
D) has an electric field to store charge that opposes a change in voltage

Question 24

The temporary condition that exists until the circuit's current or voltage reaches its steady-state value is called the

A) saturation point
B) frequency response
C) transient response
D) transit time

Question 25

The time constant is often symbolized by

A) ?
B) ?
C) $\tau$
D) ?

Question 26

In an RL circuit, the transient response is measured in terms of the ratio

A) R/L
B) L/R
C) R/X_L
D) X_L/R

Question 27

What is the time constant of a 20-H coil having 1000 ? of series resistance?

A) 0.2 s
B) 2.0 s.
C) 20 ms
D) 20 ms.

Question 28

The transient response of capacitive circuits is measured in terms of

A) R/C
B) R x C
C) 1/RC
D) 1/RX_C

Question 29

RC specifies the time it takes C to charge to what percentage of the charging voltage?

A) 37%
B) 63%
C) 70.7%
D) 29.3%

Question 30

For an RL integrator

A) the output is taken across the resistor
B) the output is taken across the inductor
C) the input must be a sine wave to get pulses at the output
D) the applied voltage cannot be dc

Question 31

Many applications of inductance are for sine-wave ac circuits, but any time the current changes; L has the effect of producing induced voltage.

Question 32

RL circuits are more common than RC circuits because inductors are smaller and more economical.

Question 33

With nonsinusoidal voltage and current, the effect of L or C is to produce a change in waveshape.

Question 34

The time constant is the time for a change of 63.2% in the current through L or the voltage across C.

Question 35

Resistance has no concentrated magnetic field to oppose a change in I, like inductance, and no electric field to store charge that opposes a change in V, like capacitance.

Question 36

While the current is building up in an RL circuit, I is changing and the inductance opposes the change; this time is called the transient response.

Question 37

The L/R time constant becomes longer with more series R.

Question 38

The transient response of capacitive circuits is measured in terms of the addition of R + C.

Question 39

RC specifies the time it takes C to charge to 63% of the charging voltage.

Question 40

The voltage across a capacitor can change instantaneously.

Question 41

Very large capacitors are sometimes placed across the terminals of a battery in order to improve the transient response of the battery.

Question 42

A capacitor can be charged slowly by a small charging current through a high resistance and then be discharged quickly through a low resistance to obtain a pulse of discharge current.

Question 43

For an RL differentiator the output is taken across the resistor.

Question 44

Time constant t = RC.