$$C_{total} = 0.923\ \mu\text{F}$$

$$4.7 \times 10$$^{-5}$$\ \text{F}$$

Question 1

Which of the following does NOT increase the inductance of a coil?

Accepted Answer

Increasing the length of the core

Question 2

A 10 H inductor is connected to a 60 Hz AC source. What is the inductive reactance $$X_L$$?

Accepted Answer

$$X_L = 600\pi\ \Omega$$

Question 3

A 120 V AC source is applied to an inductor with $$X_L = 240\ \Omega. $$What is the current?

Accepted Answer

$$I = 0.5\ 	ext{A}$$

Question 4

In an AC circuit, the current through an inductor ____ the voltage by 90 degrees.

Accepted Answer

lags

Question 5

What is the unit of inductance?

Accepted Answer

Henry

Question 6

According to Lenz’s Law, an inductor opposes a change in what?

Accepted Answer

Current

Question 7

Adding inductors in parallel will ____ the total inductance.

Accepted Answer

decrease

Question 8

A capacitor reaches 63% of its maximum charge in how many time constants?

Accepted Answer

1

Question 9

What is the total capacitance of three capacitors, 2 $$\muF$$, 4 $$\muF$$, and 6 $$\muF$$, connected in series?

Accepted Answer

$$C_{total} = 0.923\ \mu	ext{F}$$

Question 10

A 220 $$\muF $$capacitor is connected in series with a 50 k$$\Omega$$ resistor. How long does it take to fully charge the capacitor (to over 99%)?

Accepted Answer

55 s

Question 11

What is the capacitive reactance $$X_C of a 150$$ $$\muF $$capacitor at 60 Hz?

Accepted Answer

$$X_C = 17.7\ \Omega$$

Question 12

A 120 V AC source is connected to a capacitor with $$X_C = 20\ \Omega. $$What is the current?

Accepted Answer

$$I = 6\ 	ext{A}$$

Question 13

In DC, after fully charged, a capacitor behaves like what?

Accepted Answer

An open circuit

Question 14

In DC, after steady state, an inductor behaves like what?

Accepted Answer

A resistor

Question 15

Which type of capacitor is commonly used as a motor running capacitor?

Accepted Answer

Oil-filled

Question 16

Reversing polarity can damage which type of capacitor?

Accepted Answer

Electrolytic

Question 17

In a purely capacitive AC circuit, the current ____ the voltage by 90 degrees.

Accepted Answer

leads

Question 18

What is the time constant $$	au$$ for a circuit with $$R = 100\ 	ext{k}\Omega$$ and $$C = 10\ \mu	ext{F}$$?

Accepted Answer

$$	au = 1\ 	ext{s}$$

Question 19

What percentage of charge does a capacitor reach after 5 time constants?

Accepted Answer

99.3%

Question 20

Convert 47 $$\muF to $$farads.

Accepted Answer

$$4.7 	imes 10$$^{-5}$$\ 	ext{F}$$

AC Theory: Inductors, Capacitors, and Reactance – Study Notes

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