AC/DC Workbook Study Guide

If the current in each branch in a parallel circuit is 0.3 A and 0.07 A, the total current is _____A

0.37

The total resistance in a circuit containing resistors of 2 ohms, 3 ohms, 5 ohms connected in parallel is ____ ohms

0.98

The total resistance in a circuit containing resistors of 3 ohms and 5 ohms connected in parallel is ____ ohms

1.875

A conversion factor of ___________ is used to convert frequency to cycles per sec

120

Maximum out of phase condition occurs when signals are ____________ ° out of phase

180

The voltage in a parallel circuit branch that has a resistor of 3.6 k ohms and a current of 8 mA flowing through it is ____V

2.88

If the current through four loads connected in parallel in a circuit is 0.522 A, 10.25A , 7 A, and 2.9 A, the total current is ____A

20.67

The total resistance in parallel circuit that has a total current of 5.5 mA and a total voltage of 12 V is____k ohms

22

If the voltage drop across two loads connected in parallel is 24 V, the total applied voltage in the circuit is___V

24

If the voltage drop across two loads connected in parallel is 3 V, the total applied voltage in circuits is ____V

3

The voltage in a parallel circuit branch has a resistor of 5.5 ohms and a current of 6 A flowing through it is _____V

33

If the current through four loads connected in parallel in a circuit is 0.221 A, 16.73 A, 3.3 A, and 13.7 A the total current is ___A

33.95

If six loads are connected in parallel and the loads produce 60W, 75W,100W,150W,60W,401W, the total circuit power is____

485

The total resistance in a circuit containing resistors of 10 ohms, 15 ohms, 35 ohms connected in parallel is ____ohms

5.1

The total resistance in a circuit containing resistors of 8 ohms and 25 ohms connected in parallel is ___ohms

6.06

Most power in north america operates at ___________ Hz

60

The total current in a a parallel circuit that has 208 V applied to it and produces 1500 W of power is ___A

7.21

The total current flow and the the current flow through each branch of a circuit that has a total voltage of 15 V connected in parallel with a 3.5k ohms resistor and a 4.4k ohm resistor is ____A

7.7

For a two pole generator, one cycle is generated for each __________ ° of mechanical rotation of the rotor

90

An eight pole generator that delivers an output frequency of 60 Hz requires a speed of ___________ rpm.

900

___________ ride on the slip rings to remove power from a generator

Brushes

An ___________ is a negative lead of a diode

Cathode

Excessive arcing occurs at the brushes and slip rings when high levels of ___________ are present in an AC generator

Current

A silicon controlled rectifier is a solid state rectifier that is capable of rapidly switching ___________

Currents

A ___________ is one complete positive and negative alternation of a waveform

Cycle

A(n) __________ is an electronic device that allows current to flow in only one direction

Diode

__________ current is current that flows in only one direction

Direct

A frequency that is too high can cause electric motors to run slow and draw excessive current

False

A utilization voltage is a primary voltage of generators given to all loads

False

An alternation is a complete cycle.

False

An open circuit is the same as a series circuit in that any open point in the circuit causes electron flow to stop

False

DC flow occasionally reverses in direction, unlike AC.

False

Forward breakover voltage is the voltage needed to switch from a conductive state to a nonconductive state in a silicon-controlled rectifier

False

In AC circuits, voltage and current are always in phase

False

Ohm's law can be used to calculate the total circuit voltage and current, but not total circuit resistance

False

Parallel circuits are used when constant current flow from a voltage source is needed

False

The difference between a DC generator (dynamo) and an AC generator is that the AC generator has split rings (commutator), whereas the DC generator has slip rings

False

The part of the generator from which electric power is generated is known as the stator.

False

Thyristors are typically used in applications such as power control systems, battery chargers, and protection circuits.

False

Using parallel power distribution permits various loads to be connected to different power sources

False

Wavelength becomes longer as frequency is increased and is measured in meters.

False

Total current decreases if parallel loads are added and increases if parallel loads are removed

False (decreases)

As loads are added to parallel, the total current decreases

False (increases)

In a parallel circuit, the voltage drop across each load can be different

False, constant

Power is measured in ohms

False, watts

For an eight pole generator, ___________ electrical degrees are produced for each meachanical degree of rotation

Four

___________ is the number of cycles per second in an AC sine wave

Frequency

____________ broadcasting operates at 54 MHz to 216 MHz

Frequency-modulated

Another name for an alternator is an AC ___________

Generator

An even ___________ is an even multiple of a fundamental frequency

Harmonic

The __________ is the international unit of frequency equal to 1 cycle per second

Hertz

AC power is more easily distributed at ___________ voltages and lower current than DC

Higher

An ___________ is a device that changes DC power into AC power

Inverter

The shorter the period to transmission line length, the more likely the circuit is dominated by ___________

Load impedance

Wavelength is measured in ___________

Meters

Ignitrons can be wired in ___________ if greater current capacity is needed

Parallel

A __________ is the time required to produce one complete cycle of a waveform

Period

___________ is the process of changing AC to DC

Rectification

An ___________ is the relationship between a harmonic and the fundamental frequency

Sequence

A(n) ____ conductor is composed of several strands of solid wire wrapped together to make a single conductor.

Stranded

An ___________ is a solid state switching device that switches current on using a quick pulse of control current

Thyristor

__________ are electrical devices that use electromagnetism to change voltage from one level to another

Transformers

A short-circuited branch circuit has a resistance of zero

True

A stranded conductor with the same circular mil rating of a solid conductor has a greater surface area and flexibility than the solid conductor

True

AC generator output frequency is based on the number of poles and the rotational speed of the armature

True

AC is more easily distributed at higher voltages and lower current, with greater effeciency in the delivery of power.

True

AC waveforms cross the 0A baseline when there is a reversal of current flow.

True

As the resistance of a load decreases, the amount of power produced increases

True

Conductance is improves and resistance reduced when adding resistors in parallel

True

For an ignitron to conduct electricity, the anode must be positive

True

Harmonics can either be voltage harmonics or current harmonics

True

High transmission voltages are reduced to lower voltages at primary distribution transformer substations

True

If one component in a parallel circuit has a short circuit, the total resistance of the circuit is educed to 0 ohms

True

Ignitrons are useful for their ability to withstand high voltages and conduct high currents

True

In a DC parallel circuit, electrons flow in one direction

True

Lower armature rotation speed increases the life of the generator.

True

Phase is the time relationship of a sine wave to a known time period

True

Semiconductor devices make it easy to switch from AC to DC

True

Skin effect occurs in AC when more current flows near the outer surface of a conductor at higher frequencies

True

Steam powered turbines can be used to drive electric power generators

True

The strength of the electromagnet for small DC generators can be adjusted externally with fixed wiring to its field.

True

The wavelength of a signal and its frequency are proportional.

True

Total current in a parallel circuit is calculated by adding the current in all the branches

True

When current takes a shortcut around the normal path of current flow, it is referred to as a short circuit

True

For a four pole generator, ___________ electrical degrees are produced for each mechanical degree of rotation.

Two

An __________ is the unit of measure for apparent power

Volt Ampere

Alternators are rated in __________

Volt Amperes

AC generators are rated in ___________

Volt-Ampere

A __________ is the distance covered by one complete cycle of a given frequency of sound as it passes through the air.

Wavelength

___________ is equal to the velocity of the wave divided by its frequency

Wavelength

A____ resistor may be added to a parallel circuit to produce a constant flow of current

ballast

In a parallel circuit, each load is called a___ circuit

branch

Doubling the number of conductor in parallel will____the electron flow in a circuit

double

Electron flow is interrupted in a _____circuit

open

A____ circuit has two or more loads and more than one path for electron flow

parallel

Total voltage multiplied by the total circuit current yields total____in a circuit

power

Zero current flow may indicate an open between the____and a load or switch in the circuit

power source

When only two resistors are in parallel, the____method reduces to the product over the sum of resistors values

reciprocal

The voltage drop in a parallel circuit_______across each load

stays the same

Total power of a parallel circuit is equal to the____of the power produced by each load

sum