Deck 18: Capacitive Reactance

Question 1

When a capacitor charges and discharges with a varying voltage applied, ______________ current can flow.

Answer 1

alternating

Question 2

The symbol for ______________ reactance is X_C.

Answer 2

capacitive

Question 3

The base unit for capacitive reactance is the ______________.

Answer 3

ohm

Question 4

For a capacitor, the charge and discharge current flows to and from the plates not through the ______________.

Question 5

A very common application for a capacitor is to block ______________.

Question 6

Capacitive reactance is a measure of a capacitor's ______________ to the flow of alternating current.

Question 7

In the formula for capacitive reactance, the constant factor 2π is always ______________.

Question 8

Capacitive reactance is ______________ proportional to frequency.

Question 9

When analyzing electronic circuits, capacitors are often treated as a ______________ for ac.

Question 10

For parallel reactances, the combined reactance is calculated by the ______________ formula.

Question 11

The symbol for capacitive reactance is

A) Z_C
B) C_X
C) X_C
D) R_X

Question 12

A measure of a capacitor's opposition to the flow of alternating current is

A) resistance
B) impedance
C) inductive reactance
D) capacitive reactance

Question 13

X_C equals

A) 1/2?fC
B) 2?fC
C) 2?/fC
D) 1/2?C

Question 14

In the formula for capacitive reactance, the constant factor 2? is always

A) 3.24
B) 3.14
C) 6.28
D) 2.82

Question 15

How much X_C will there be if the capacitance is 10 ?F and the frequency is 1400 Hz?

A) 1140 ?
B) 114 ?
C) 11.4 ?
D) 1.14 ?

Question 16

Which of the following is correct?

A) X_C is inversely proportional to capacitance
B) X_C is directly proportional to capacitance
C) X_C is directly proportional to frequency
D) X_C is not affected by frequency

Question 17

Because of the inverse relation between X_C and f or C, the graph of X_C versus C is

A) impossible to plot
B) nonlinear
C) linear
D) exponential

Question 18

When analyzing electronic circuits, capacitors are often treated as

A) an open for ac and a short for dc
B) an open for dc and a short for ac
C) a large resistor for high frequencies
D) an ac amplifier

Question 19

What is the total capacitive reactance in a series circuit if three capacitors offered 150 ? of reactance each?

A) 50 ?
B) 150 ?
C) 450 ?
D) not enough information given

Question 20

For parallel reactances, the combined reactance is calculated by

A) the reciprocal formula
B) adding each reactance
C) adding each reactance and then dividing by the number of reactances
D) dividing the value of one reactance by the number of reactances

Question 21

In a capacitive circuit, if the applied voltage is an rms value

A) all calculated currents and voltage drops are also rms values
B) all calculated currents and voltage drops must be peak values
C) all calculated currents and voltage drops are average values
D) all calculated currents and voltage drops are peak-to-peak values

Question 22

The rate of voltage change, d_v/d_t, for a sine wave, is determined by its

A) amplitude only
B) frequency only
C) current
D) amplitude and frequency

Question 23

What ratio specifies the capacitive reactance in ohms?

A) v_c/i_c
B) i_c/v_c
C) d_v/d_t
D) X_C/i_c

Question 24

When a capacitor charges and discharges with a varying voltage applied, alternating current can flow.

Question 25

The base unit for capacitive reactance is the siemens.

Question 26

For a capacitor, the charge and discharge current flows to and from the plates and through the dielectric.

Question 27

A very common use of a capacitor is to provide little opposition for ac voltage but to block any dc voltage.

Question 28

Capacitive reactance is a measure of a capacitor's opposition to the flow of direct current.

Question 29

In the capacitive reactance formula, the constant factor 2? is always 2 times 3.14, which equals 6.28.

Question 30

Capacitive reactance is inversely proportional to the capacitance.

Question 31

When analyzing electronic circuits, capacitors are often treated as an open for dc and as a short for ac.

Question 32

Series or parallel capacitive reactances are combined in the same way as capacitances.

Question 33

The general use of capacitive reactance is to block direct current but provide low reactance for alternating current.

Question 34

The rate of voltage change, d_v/d_t, for a sine wave, is determined by both its amplitude and its frequency.

Question 35

There is no capacitive charge or discharge current when an applied ac source is not changing.

Question 36

In a capacitive circuit, instantaneous voltage and current are 180° out of phase.

Question 37

The symbol for capacitive reactance is C_X.