RC Series Circuits

Question 1

The total capacitance (Ct) of a series circuit is always less than ______.

Answer 1

The total capacitance (Ct) of a series circuit is always less than the smallest capacitor.

Question 2

To find total capacitance (Ct) in a series circuit, what formula is used?

Answer 2

Question 3

Capacitive reactance (Xc) in a series circuit is measured in _____ and expresses the amount of __________.

Answer 3

Capacitive reactance (Xc) in a series circuit is measured in ohms and expresses the amount of opposition to current flow in the circuit.

Question 4

As capacitance increases, current _____, and capacitive reactance ______.

Answer 4

As capacitance increases, current increases, and capacitive reactance decreases.

Question 5

Review Question:

How is frequency measured?

Answer 5

Frequency is measured in cycles per second. The more cycles per second, the higher the frequency.

Question 6

As frequency increases, current _____, and capacitive reactance _______.

Answer 6

As frequency increases, current increases, and capacitive reactance decreases.

Question 7

Combining the effects of capacitance and frequency produces what formula for capacitive reactance?

Answer 7

Xc = 1 ÷ (2)(pie)(f)(C)

Question 8

As frequency increases, Xc ______.

Answer 8

As frequency increases, Xc decreases.

Question 9

As capacitance increases, Xc ______.

Answer 9

As capacitance increases, Xc decreases.

Question 10

What is the formula for total capacitive reactance (Xct)?

Answer 10

Total Xc is determined by adding each capacitor’s capacitive reactance.

Xct = Xc₁ + Xc₂ + Xc₃…..

Question 11

The combined opposition to current flow from the resistor and capacitor is called _____. The unit of measure is ______.

Answer 11

The combined opposition to current flow from the resistor and capacitor is called impedance (Z). The unit of measure is ohms.

Question 12

What is the formula for total impedance (Zt)?

Answer 12

Zt = Sq Rt of R² + Xc²

Question 13

What steps is needed to solve for total current and voltage drops in an example circuit?

Answer 13

1. Calculate capacitive reactance. Xc = 1 ÷ (2)(pie)(f)(C)
2. Find total capacitive reactance. Xct = Xc₁ + Xc₂……
3. Determine total resistance. Rt = R₁ + R₂…..
4. Solve for total impedance. Zt = Square Root of: Rt² + Xct²
5. Solve for total current. It x ‘R’ = V
6. Solve for voltage drops.

• Er = It x R
• Ec = It x Xc

7. Check the results. Applied Voltage Ea = Sq Rt of: Ert² + Ect²

Question 14

In AC circuits with reactance, what are the three types of power?

Answer 14

Real - the power consumed by the resistor.

Reactive - the power consumed by the capacitor.

Appearent - the combination of real power and reactive power.

Question 15

What is the phase relationship between current and voltage across a capacitor?

Answer 15

I leads E by 90 degrees.

To help remember this relationship, remember the word ICE. Current (I) in a capacitive circuit (C) is before voltage (E). Current leads voltage.

Question 16

RL series circuits consist of _______ and _______ connected in series.

Answer 16

inductors, resistors

Question 17

In RL series circuits, R and XL oppose _____at right angles

Answer 17

oppose current at right angles

Question 18

In RL series circuits, _____ is the same at any point in the circuit

Answer 18

current is the same at any point in the circuit

Question 19

In RL series circuits, _____ and ____ are at right angles.

Answer 19

In RL series circuits, ER and EL are at right angles.

Question 20

In an RL series circuit, as the phase angle approaches 90 degrees, the circuit is mostly _______.

Answer 20

inductive

Question 21

In RL series circuits _____ leads current by 90 degrees.

Answer 21

voltage leads current by 90 degrees

Question 22

In an RL series circuit, as the phase angle approaches 0 degrees, the circuit is mostly _______.

Answer 22

resistive

Question 23

When measuring across a resistor, _______ and _______ are always in phase.

Answer 23

voltage and current

Question 24

As XL increases, a circuit becomes more _______.

Answer 24

inductive

Question 25

When XL is large compared to R in an RL series circuit, the circuit is _______.

Answer 25

inductive