Deck 21: Capacitance in Alternating Current Circuits

Question 1

What is the reactance of a 25 μ F capacitor when the applied frequency is 400 Hz?

A) 10.61 Ω
B) 11.59 Ω
C) 15.92 Ω
D) 16.12 Ω

Answer 1

C

Question 2

Three capacitors, a 12 ? F, a 20 ? F, and a 30 ? F, are connected in series to a 400 Hz source. What is the total XC ?

A) 36.42 ?
B) 42.78 ?
C) 52.09 ?
D) 66.32 ?

Answer 2

66.32 ?

Question 3

Three capacitors, a 12 μ F, a 20 μ F, and a 30 μ F, are connected in series to a 60 Hz source. What is the total X_C?

A) 226.42 Ω
B) 342.78 Ω
C) 442.09 Ω
D) 566.32 Ω

Answer 3

C

Question 4

What is the symbol for capacitive reactance?

A) C
B) X_C
C) L
D) X_L

Question 5

Two capacitors, a 20 μ F and a 30 μ F, are connected in series to a 400 Hz source. What is the total capacitive reactance?

A) 7.96 Ω
B) 33.16 Ω
C) 42.04 Ω
D) 53.05 Ω

Question 6

The voltage rating of a capacitor _____.

A) can be exceeded as long as the time is under one hour
B) should never be exceeded
C) is only a suggested maximum
D) is a minimum working voltage

Question 7

The quality of a capacitor is found by Q = _____.

A) X_C/R
B) R/X_C
C) PF
D) W/VARs

Question 8

A capacitor is connected to a 240 V supply. An ammeter indicates 3 A. What is the capacitive reactance of the capacitor?

A) 23 Ω
B) 30 Ω
C) 71 Ω
D) 80 Ω

Question 9

​When the voltage and current have _____ polarities in a pure capacitive circuit, the capacitor is discharging and the energy is returned to the circuit.

A) ​the same
B) ​opposite

Question 10

The power in a capacitor is reactive power. What is the unit for reactive power?

A) W
B) VA
C) P
D) VAR

Question 11

In a circuit containing a capacitor, the impressed voltage is _____ with the applied voltage.

A) 180 ° out of phase
B) 90 ° out of phase
C) in phase
D) 270 ° out of phase

Question 12

Two capacitors, a 20 μ F and a 30 μ F, are connected in series to a 60 Hz source. What is the total capacitive reactance?

A) 117.96 Ω
B) 221.04 Ω
C) 253.05 Ω
D) 333.16 Ω

Question 13

The capacitive reactance of a capacitor is _____ proportional to frequency.

A) directly
B) inversely

Question 14

In a pure capacitive circuit, the current _____ the applied voltage by _____.

A) leads; 180 °
B) lags; 180 °
C) leads; 90 °
D) lags; 90 °

Question 15

When a capacitor is connected to a(n) _____ circuit, current appears to flow through the capacitor.

A) DC
B) AC

Question 16

What is the unit for capacitive reactance?

A) ohm
B) farad
C) henry
D) coulomb

Question 17

What is the reactance of a 10 pF capacitor when the applied frequency is 30 Hz?

A) 200.36 Ω
B) 325.76 Ω
C) 530.52 Ω
D) 612.83 Ω

Question 18

A 35 μ F capacitor is connected to a 60-Hz, 120 V supply. What is the X_C of the capacitor?

A) 75.79 Ω
B) 80.33 Ω
C) 83.2 Ω
D) 93.43 Ω

Question 19

A 1 μ F capacitor has 2,652 Ω of reactance at 60 Hz. What is the reactance value at 400 Hz?

A) 397.88 Ω
B) 568.72 Ω
C) 639.79 Ω
D) 768.33 Ω

Question 20

Countervoltage presented by a capacitor is called _____.

A) capacitance
B) inductance
C) capacitive reactance
D) inductive reactance

Question 21

Three capacitors, a 12 μ F, a 20 μ F, and a 30 μ F, are connected in parallel to a 400 Hz source. What is the total X_C?

A) 6.42 Ω
B) 42.78 Ω
C) 44.09 Ω
D) 56.32 Ω

Question 22

Two capacitors, a 20 μ F and a 30 μ F, are connected in parallel to a 400 Hz source. What is the total capacitive reactance?

A) 7.96 Ω
B) 33.16 Ω
C) 42.04 Ω
D) 53.05 Ω

Question 23

Two capacitors, a 20 μ F and a 30 μ F, are connected in parallel to a 60 Hz source. What is the total capacitive reactance?

A) 7.96 Ω
B) 23.16 Ω
C) 42.04 Ω
D) 53.05 Ω

Question 24

Three capacitors, a 12 μ F, a 20 μ F, and a 30 μ F, are connected in parallel to a 60 Hz source. What is the total X_C?

A) 6.42 Ω
B) 42.78 Ω
C) 442.09 Ω
D) 566.32 Ω