Deck 4: Series Circuitsresistance and Impedance

Question 1

The name ____________________ is given to the action whereby alternating current is forced toward the surface of a conductor.

Answer 1

skin effect

Question 2

Describe the effective resistance effect.

Answer 2

The effective resistance is the resistance that a circuit or component offers to alternating current. Also known as ac resistance, it may vary with the frequency, current, or voltage of the circuit. Effective resistance must not be confused with impedance. The quantity resulting from the combination of effective resistance and reactance is impedance.

Question 3

Describe dielectric losses.

Answer 3

As the impressed voltage rises to a maximum value twice in each cycle, a voltage stress is placed on the insulation of the conductor. Such a stress occurs first in one direction and then in the other. As a result, there is a small heat loss in the insulation. This loss is called the dielectric loss and is very small when compared to the other losses in the circuit due to the skin effect, eddy currents, and hysteresis. Usually the dielectric loss can be neglected.

Question 4

To obtain high values of inductance, ____________________ cores are usually required.

Question 5

The base of an impedance triangle represents the ____________________.

Question 6

The power factor of the entire series circuit is the ____________________ of the total true power in watts to the total apparent power in volt-amperes.

Question 7

A low value of Q means that the resistance component is relatively low.

Question 8

Because of the skin effect, there is more useful copper conducting area with alternating current.

Question 9

A large Q is desirable because it means that the useful inductive reactance is high and the effective resistance is low.

Question 10

What is the figure of merit?

Question 11

Explain eddy current loss.

Question 12

Reactors that have a high Q value are often treated as pure inductors, and the amount of wire resistance is ignored because it is such a small part of the total impedance of the coil.

Question 13

The ____________________ of a coil is the result of the combination of the effective resistance and inductive reactance.

Question 14

The impedance section of each circuit considered consists of a reactor having a relatively large inductive reactance compared to the effective resistance.

Question 15

Explain hysteresis losses.