Tom

A balanced three wire, 120/240 V, single phase circuit is connected so that the ungrounded conductors are from different transformer phases line 1 and line 2. The current on the neutral conductor will be______% of the ungrounded conductor current.

0%

Three phase AC generators have three equally spaced windings,______degrees out of phase with each other.

120

If the output is 1600 W and the equipment is 88% efficient, what are the input amperes at 120 V?

15 A

What is the power loss in watts of a conductor that carries 24 A and has a voltage drop of 7.20 V?

175 watts, P= IxE

If the primary phase voltage is 480 V and the secondary phase voltage is 240 V, returns ratio is______.

2 to 1 ratio

What size transformer is required for a 100 amp, 240 V, single phase non-continuous load that has a power factor of 85%?

25 kVA

An electrical arc glass can approach______, which vapor rises metal parts and produces both in deadly pressure waves.

30,000°F

Arcing is defined as a luminous discharge of electricity across an insulating medium. Electric arcs operate at temperatures between______and expel small particles of very hot molten material.

5000 and 15,000°F

What is the nameplate FLA for a 20 hp, 208 V, three phase motor with 90% power factor and 80% efficiency?

58 A

What is the voltage drop of 2 12 AWG conductors (.40 ohms) supplying a 16 amp load, located 100 feet from the power supply? Formula Evd = I X R

6.4 volts

How many 20 amp, 120 V circuits are required for 42, 300 W Lumineers noncontinuous load that have a power factor of 85%?

7

The formulas in the formula will apply to______

AC with unity power factor

The induced voltage in a conductor carrying alternating current opposes the change in current flowing through the conductor. The induced voltage that opposes the current flow is called______.

CEMF, counter electromotiveforce, back EMF

Wasteful circulating______in the iron core causes the core to heat up without any useful purpose.

Eddy currents

______Can be reduced by dividing the core into many flat sections or laminations.

Eddy currents

For AC circuits, the AC______of a conductor must be taken into consideration.

Eddy currents, skin effect, resistance

The total resistance of a parallel circuit can be calculated by______method.

Equal resistance, product over sum, reciprocal.

A GFCI protection device contains an internal monitor that prevents the device from being turned on if there is a neutral to case connection downstream of the device but this only occurs if there is a load on the circuit.

False

A holding relay is primarily use for work or convenience.

False

AC inductive or capacitive reactive loads cause the voltage and current to be in phase with each other.

False

In a DC circuit, the only opposition to current flow is the physical resistance of the material. This opposition is called reactance and is measured in ohms.

False

Inverse time breakers operate on the principal That as the current decreases, the time it takes for the device to open decreases.

False

Lightning protection is intended to protect the building itself as well as the electrical equipment on or inside the structure.

False

Magnetic lines of force can cross each other and they are called flux lines.

False

Non-magnetic metals are ferrous meaning they do not contain any iron and cannot be magnetized.

False

The best conductors, in order of the conductivity, are gold, silver, copper, and aluminum.

False

The motor FLA rating is used when sizing motor conductors size or circuit protection.

False

The termination of the lightning strike is unlikely to ignite combustible materials.

False

To prevent fires and electric shock, the NEC specifies that neutral current can flow on metal parts of the electrical system.

False

Three-phase, ____ wye-connected systems can overheat because of circulating odd triplen harmonic currents.

Four wire

Because of the dangers associated with an open neutral conductor, the continuity of the______conductor cannot be dependent upon the receptacle.

Grounded

Because of the earths______resistance to current flow, it cannot be used for the purpose of clearing a line to case ground fault.

High

As current flows through the transformer, the iron core is temporarily magnetized. The energy required to realign the core molecules to the changing electromagnetic field is called______loss.

Hysteresis

The total opposition to current flow in AC circuits is called______and measured in ohms.

Impedance

Transformers are rated in______.

KVA

If the rotating part of the motor winding is jammed so that it cannot rotate, no CEMF will be produced in the motor winding. Result the motor operates at______and the windings will be destroyed by excessive heat.

LRC

A clamp on a CM meter has a coil that is clamped around the conductor and detects the rising and falling______field being produced due to the arc flow through the conductor.

Magnetic

The electric motor works on the principle of the attracting and repelling forces of______fields.

Magnetic

Factors that affect the available short circuit current include circuit conductor______.

Material, size, length

A non-sinusoidal wave form is created when______loads distort the voltage and current sine wave.

Nonlinear

The purpose of overcurrent protection is to protect the conductors and equipment against excessive or dangerous temperatures because of overcurrent. Overcurrent is current in excess of the rated current of equipment or conductors. it may result from an______.

Overload, short circuit, ground fault.

To protect against electric shock or to prevent a fire, a dangerous______must quickly be removed by opening the circuits overcurrent protection device.

Overload, short circuit, ground fault.

Improper wiring or miss handling of multi wire branch circuits can cause______connected to the circuit.

Overloading of the ungrounded conductors, overloading of the neutral conductors.

Dual voltage AC motors are made with two field windings. The Field windings are connected in______for low-voltage operation and in______for high-voltage operation.

Parallel, series

What is the resistance of the circuit conductors when the conductor voltage drop is 7.20 V and the current flow is 50 A?

R= E/I .14 ohms

Ohmmeters measure the______or opposition to current flow of a circuit or component.

Resistance

The Megger is used to measure a very high______values, such as those found in cable insulation, or motor and transformer windings.

Resistance

The______of a generator is forced to rotate while it is being subjected to the magnetic field of the stator.

Rotor

The______of an AC generator contains the electromagnetic field, which cuts through the stationary conductor coils.

Rotor

EQUIPMENT must have an______current rating that permits the protection device to clear a short circuit or ground fault without extensive damage to the components of the circuit.

Short circuit

The magnetic time delay circuit breaker operates on the solenoid principle where a movable core, held with a spring, is moved by the magnetic field of An ______.

Short circuit, ground fault.

When a motor starts, the current drawing is approximately______times the motor FLA, this is known as motor locked rotor amperes LRA.

Six

The expanding and collapsing magnetic field within the conductor induces a voltage into conductors CEMF that repels the flowing electrons toward the surface of the conductor. This is called______.

Skin effect

In an______motor, the rotor is locked in step with the rotating stator field and is dragged along at the speed of the rotating magnetic field.

Synchronous

Kerchoff's current law states, in a series circuit, the current is______through the transformer, the conductors, and the appliance.

The same

The______Sensing element causes the circuit breaker to open when a predetermined calibration temperature is reached.

Thermo

The effective value is equal to the peak value______.

Times 0.707

According to the conventional current flow theory, electrons travel from the positive to negative.

Trail

According to Kerchoff's current law, the total current provided by the source to a parallel circuit will equal the sum of the currents of all of the branches.

True

According to the electron current flow theory electrons flow away from the negative terminal of the source through the circuit and load, toward the positive terminal of the source.

True

An AFCI protection device provides protection from an arcing fault by recognizing the characteristics unique to an arcing fault and by functioning to denergize the circuit when an arc fault is detected.

True

Available short circuit current is the current in amperes available at a given point in the electrical system.

True

Because of conductor resistance, flux leakage, Eddy currents, and hysteresis losses, not all of the input power is transferred to the secondary winding for useful purposes.

True

Circuit breakers and fuses are intended to interrupt the circuit, and they must have an ampere interrupting rating sufficient for the available short circuit current.

True

Electrons leaving a power supply are always trying to return to the same power supply; they are not trying to go into the earth.

True

Even when power is removed from the circuit, capacitors can store large amounts of energy for a long period of time. They can discharge an arc if inadvertently shorted or grounded out.

True

If a conductor carrying current is next to another conductor carrying current in the opposite direction, the electromagnetic field attempts to push the conductors apart.

True

If the protection device is not rated to interrupt the current at the available fault values at its listed voltage rating, it can explode while attempting to clear the fault.

True

If the ungrounded conductors of a multiwire circuit Are not terminated to different phases, this can cause the neutral current to be in excess of the neutral conductor rating.

True

In an AC induction motor, the stator produces a rotating magnetic field that induces current in the rotor windings. The rotor current generates a magnetic field in opposition to the magnetic field of the stator, there by causing the rotor to turn.

True

It is not the force of the magnetic field through a conductor that produces electricity, it is the relative motion of the field to the electrons within the conductor that produces the movement of electrons.

True

Kerchoff's voltage law states, in a series circuit, the sum of the voltage drops across all of the resistors will equal the applied voltage.

True

Lightning frequently terminates to a point of elevation and strikes non-metallic as well as metallic objects with the same frequency.

True

Metal parts of premises wiring must be bonded to a low impedance path designed so that the circuit protection device will quickly open and clear a ground fault.

True

People become injured in death occurs when voltage pushes electrons through the human body causing the heart to go into ventricular fibrillation.

True

Providing a path to earth often helps reduce electro static charge.

True

Severe electric shock or death can occur if a person touches the ungrounded and the neutral conductors at the same time, even if the circuit is GFCI protected.

True

The current flowing on the neutral conductor of a multi wire circuit is called unbalance current.

True

The energy transfer ability of a transformer is accomplished because the primary electromagnetic lines of force induce a voltage in the secondary winding.

True

The heating from harmonic currents is proportional to the square of the harmonic current.

True

The major advantage of a AC over DC is the ease of voltage regulation by the use of a transformer.

True

The opposition to current flow results in Voltage Drop.

True

The severity of an electric shock is dependent on the current flowing through the body, which is impacted by circuit voltage and contact resistance.

True

Typically, when a GFCI protection device fails, the switching contacts remain closed and the device will continue to provide power without GFCI protection.

True

Unsafe arcing faults can occur in one of two ways, as series arcing faults or as parallel arcing faults. The most dangerous is the parallel arcing fault.

True

Voltage induced in the secondary winding of a transformer is dependent on the number of secondary turns as compared to the number of primary turns.

True

When power supplies are connected in parallel, the voltage remains the same, but the current or amp hour capacity will be increased.

True

Swapping______of the line conductors can reverse a three phase AC motors rotation.

Two

A GFCI is designed to protect persons against electric shock. It operates on the principle of monitoring the imbalance of current between the circuits______conductor.

Ungrounded, grounded

______Motors are fractional horsepower motors that operate equally well on AC and DC and are used for vacuum cleaners, electric drills, mixers, and light household appliances.

Universal

When describing the relationship between voltage and current the reference waveform is always _______.

Voltage

Factors that affect the available short circuit current include transformer______.

Voltage, KVA rating, impedance.

Self induced voltage opposes the change in current flowing in the conductor. This is called inductive reactance and it is abbreviated______.

XL

The opposition offered to the flow of AC current by a capacitor is called capacitive reactance, which is expressed in ohms and abbreviated______.

Xc

The abbreviation for impedance is______.

Z