An AC generator has all of the following except:
A. a commutator
B. a magnetic field
C. slip rings
D. a conductor in relative motion with the magnetic field
A. a commutator
A ground detector measures __________________________.
A. insulation resistance to ground
B. difference in phase currents
C. difference in phase voltage
D. current on the neutral connection
A. insulation resistance to ground
Match the sub-system of the electrical distribution system with the appropriate definition.
- One or more electrical substations, where the incoming high voltage is transformed down to a lower voltage
- Includes the high-voltage cables, power poles, and switching stations forming a “grid” which extends across the industrial facility.
- Transform incoming high voltage down to a value usable by the facility and distribute it to electrical equipment throughout the facility.
- Equipped with a main supply breaker to receive power and several feeder breakers to supply power to various motor control centers in the facility and larger electrical loads
A. Substations
B. Load centers
C. Distribution system
D. Transmission system
- C
- D
- A
- B
Match the terms with the appropriate description.
- Used in electrical power distribution and transmission systems
- Sometimes used in electrical circuits to ensure that a fault developed in one portion of the circuit will not affect another portion of the circuit
- Consists of only one winding
- Steps down the voltage of an electrical circuit to a low value that can be effectively and safely used for the operation of instruments
A. Isolation transformer
B. Auto transformer
C. Distribution transformer
D. Instrument potential transformer
- C
- A
- B
- D
When two AC voltages reach their peak voltage at the same time, the voltages are said to be __________________.
A. leading
B. lagging
C. in phase
D. out of phase
C. in phase
Which of the following are common three-phase to single-phase connection methods? (select all that are correct)
A. Phase to line
B. Phase to ground
C. Phase to phase
D. Neutral to ground
B. Phase to ground
C. Phase to phase
Match the terms with their appropriate definitions.
- Voltage on the primary side divided by voltage on the secondary side
- Ratio of primary turns to secondary turns
- A transformer with higher secondary voltage than primary voltage
- A transformer with lower secondary voltage than primary voltage
A. Step-up transformer
B. Step-down transformer
C. Voltage ratio
D. Turns ratio
- C
- D
- A
- B
A multimeter can be used to measure all of the following except_____________________.
A. AC voltage
B. DC voltage
C. hysteresis
D. resistance
C. hysteresis
A capacitor is ________________________________.
A. two metal plates separated by an insulating material that opposes a change in current flow
B. two metal plates separated by an insulating material that opposes a change in voltage
C. a coil of wire around a magnetic core that opposes a change in voltage
D. a Coil of wire around a magnetic core that opposes a change in current flow
B. two metal plates separated by an insulating material that opposes a change in voltage
The peak value of voltage in an AC circuit is 250 volts. Calculate the effective voltage.
A. 120 volts
B. 125 volts
C. 177 volts
D. 353 volts
C. 177 volts
Effective voltage (RMS) = Peak voltage X 0.707
Peak voltage = Effective voltage (RMS) / 0.707
Which of the following is not an advantage of three-phase systems?
A. Three-phase equipment weighs less than single-phase equipment with the same rating.
B. Three-phase equipment is smaller than single-phase equipment of the same rating.
C. Three-phase equipment is more efficient than single-phase equipment.
D. Three-phase equipment is DC, so there is no need for transformers.
D. Three-phase equipment is DC, so there is no need for transformers.
Match the terms with their appropriate description.
- An electro-mechanical device that controls power to a piece of equipment
- Receives power from a substation and supplies power to facility motor control centers and larger electrical loads
- Small distribution panels, which contain numerous molded-case circuit breakers. Usually provide power to 208 VAC or 120 VAC loads.
- Circuit breaker, which receives power from a switchgear buss bar and directs the power to downstream electrical loads
A. Contactor
B. Feeder breaker
C. Load center
D. Panel
- A
- C
- D
- B
Match the power terms with their appropriate location on the power triangle.
Apparent power
Reactive power
True power
A. Apparent power
C. True power
B. Reactive power
Select all of the statements about inductors that are true.
A. An inductor is a circuit element that will store electrical energy in the form of a magnetic field.
B. An inductor stores energy as a stored charge between two plates.
C. An inductor is usually a coil of wire wrapped around a core of permeable material.
D. Inductors oppose a change in voltage.
A. An inductor is a circuit element that will store electrical energy in the form of a magnetic field.
C. An inductor is usually a coil of wire wrapped around a core of permeable material.
The _________________________ is normally confined to protected environments such as fully enclosed ducts or overhead transmission lines that cannot be reached by personnel without extraordinary means.
A. 4-wire, three-phase delta system
B. Ungrounded delta system
C. Edison system
D.4-wire, three-phase Wye system
B. Ungrounded delta system
Adding a capacitor to an inductive circuit will _______________________.
A. reduce the impedance, because the capacitive reactance counteracts some of the inductive reactance
B. increase the impedance, because all reactance adds to the impedance
C. reduce the resistance of the circuit
D. cause no change to the circuit at all, since it is primarily inductive
A. reduce the impedance, because the capacitive reactance counteracts some of the inductive reactance
What is True power?
the power consumed by the resistive loads in an electrical circuit.
A three-phase Wye-connected system with an unbalanced load will have a neutral current of zero.
A.False
B.True
A.False
•When the three load impedances are not equal to one another, the phasor sums and the neutral current (In) are not zero, and the load is unbalanced
Match the terms with their appropriate definitions.
- Inducing an EMF in a coil by magnetic lines of flux generated in another coil
- The ratio of the number of turns of wire in the primary winding to the number of turns of wire in the secondary winding
- The ratio between the two impedances
- The ratio of the power output to the power input
A. Efficiency
B. Mutual induction
C. Impedance ratio
D. Turns ratio
- B
- D
- C
- A
Match the terms to their appropriate definitions.
- The time required for the generator to complete one cycle
- The number of cycles completed per second
- The magnitude of voltage or current range spanned by the sine wave.
- The root of the mean (average) square of the currents or voltages
A. Period
B. Peak-to-peak
C. Frequency
D. RMS
- A
- C
- B
- D
Parameters normally measured by installed meters include _________. (select all that are true)
A. hysteresis
B. power (watts)
C. voltage
D. current (amps)
B. power (watts)
C. voltage
D. current (amps)
What is reactive power?
the power component in an AC circuit necessary for the expansion and collapse of magnetic (inductive) and electrostatic (capacitive) fields. Volt-amperes-reactive (VAR) are the units for Reactive Power.
Match the terms to the appropriate description.
- The coil that is energized by the AC source
- The coil that is connected to the load
- Magnetic material that the coils are wound around
- Magnetic flux that passes through only one of the coils
A. Leakage
B. Primary
C. Secondary
D. Core
- B
- C
- D
- A
Match the terms with the appropriate definitions.
- The current in amperes that a conductor can carry continuously under the conditions of use without exceeding its temperature rating
- A conducting connection, whether intentional or accidental, between a circuit or piece of equipment and the earth, or some body serving as earth; a place of zero electrical potential
- A current-carrying conductor normally tied to ground so that the electrical potential is zero
- Permanent joining of metallic parts or circuits assuring electrical continuity and capacity to safely conduct any current
A. Ampacity
B. Bond
C. Ground
D.Neutral
- A
- C
- D
- B
