Worksheet 8-Generating Electrical Power

Question 1

Define alternating current.

Answer 1

AC is the flow of electrons that continually changes its value in magnitude and periodically reverses electric polarity.

Question 2

What is frequency?

Answer 2

Frequency is the number of times per second that alternating current starts at 0 volts, then cycles through maximum positive voltage, maximum negative voltage then back to 0 volts. The number of 360 degree alternations per second.

Question 3

What is the unit of measure for AC frequency?

Answer 3

Frequency is define and the number of cycles of alternating current per second is expressed in Hertz (Hz)

Question 4

What is the measure of a Hz?

Answer 4

A Hertz is measured in cycles per second.

Question 5

What is the resistance to current flow that can exist in an AC circuit?

Answer 5

Impedance is the resistance to current flow in an AC circuit.

Question 6

What is a part of electrical impedance to AC when compared to electrical properties of capacitors and inductors?

Answer 6

Reactance is the portion of electrical impedance that is caused by either an inductor or capacitor.

Question 7

What is the opposition of current flow that is produced by a capacitor?

Answer 7

Capacitive reactance.

Question 8

What is the phase relationship in a capacitance circuit between current and voltage?

Answer 8

Current (I) Leads Voltage (E) in a capacitive circuit (ICE)

Question 9

Write out the mathematical formula for Capacitive Reactance.

Answer 9

X_C= 1 / 2 ∏ f C

Question 10

What is the current to voltage relationship in a purely inductive circuit?

Answer 10

Voltage (E) leads Current (I) in an inductor circuit (ELI)

Question 11

What is the mathematical formula you would use to determine Inductive Reactance?

Answer 11

X_C= 2 ∏ f C

Question 12

How is a sine wave plotted?

Answer 12

A sine wave has plots that start at 0, move through 90, 180, 270 and then back to 0. A full 360 degree cycle.

Question 13

In a sine wave at what plot or position of the magnetic field are the current and voltage at maximum values?

Answer 13

When a conductor is passing through 90 and 270 degrees, assuming that the conductor starts at 0 outside of the magnetic field.

Question 14

What is the effective value of power of an AC voltage when compared to a DC voltage?

Answer 14

The effective value of power for an AC signal is Root Mean Square of peak voltage.

Question 15

How is peak voltage calculated for an AC signal?

Answer 15

V_RMS = 0.707 x V_PEAK

Question 16

What is the measure between two or more signals that are not perfectly timed to each other?

Answer 16

Phase angle is the difference between two or more combined signals.

Question 17

What is the measure of a ratio of power dissipated over the power input into the circuit?

Answer 17

The power factor is the ratio between the input power compared to the power expended.

Question 18

What is the phantom power that is expended in a circuit due to the energy expended by capacitors and inductors?

Answer 18

Reactive power is that power lost in a circuit due to capacitors and inductors.

Question 19

For three phase motor winding methods, which method of motor winding has all of the windings connected to a common point?

Answer 19

A Wye Wound motor has all phases connected to a common electrical node.

Question 20

What is a three phase motor also known as, when describing the output signal waveform?

Answer 20

A three phase motor is also known as a polyphase winding 120 degrees apart.

Question 21

What device converts an AC signal into a type of DC output?

Answer 21

A rectifier is a device that converts AC signals into DC signals.

Question 22

What electrical device will convert a DC input into a type of AC output?

Answer 22

An inverter will convert DC input into a type of AC output.

Question 23

What is it called when a meter is placed between the voltage source and load and a reduction is measured?

Answer 23

A voltage drop is measured between a voltage source and load.

Question 24

What is being described when an algebraic sum of current flowing away from a single point is equal to the sum of all current flowing to that same point?

Answer 24

Kirchhoff’s Current Law

Question 25

What is a device that splits current flow into two paths for the purpose of taking a measurement between the two paths?