Master Electrical Closed Book Exam Questions

A device capable of drawing lightning discharge to it in preference to vulnerable parts of the protected area is a ________.

( air terminal ) - also known as a electric rod, most commonly installed lightning protection system

In an AC circuit a value of watts divided by a value of volt-amps, what should the power factor be to indicate close to unity?

( high power factor) = having a high power factor, tells you, that the POWER FACTOR is close to unity(1.0). Which is what you want in a circuit. Because that means that the power is IN PHASE and this is called TRUE POWER. We don't want to have a low power factor, because that means the circuit power is OUT OF PHASE , meaning that you have to much inductance or capacitance, which is called APPARENT POWER.

If you double the voltage in a circuit and cut the resistance in half, the current will become ________.

(Four times as great), example: 10v / 2 ohm = 5 amps, if you double the voltage and cut the resistance in half, 20v / 1 ohms = 20 amps

If the length and area of a cross-section of a wire are doubled, then it's resistance _________.

(Remains the same)- key words in the question, length and area, only when the area (csa) doubled and not both length and csa. Doubling the csa only will cut the resistance by 1/2

If the DC resistance of a #500 kcmil copper conductor 1000 feet in length is .0258 ohm, the DC resistance for a #1000 kcmil copper conductor 1000 feet in length would be ________ ohm.

0.0129, is because if you double the cross-sectional area (csa) of a conductor it will reduce the resistance by 1/2. .0258/2= .0129

A good conductor material should have how many valence electrons?

1

List the four best conductors in order for electricity?

1. Silver, 2. Copper, 3. Gold, 4. Aluminum

Conductors drawn from a copper-clad aluminum rod with the copper metallurgically bonded to an aluminum core. The copper forms a minimum of ________ percent of the csa.

10

The minimum cover requirement for rigid nonmetallic conduit without concrete encasement is ________ inches.

18"

Flexible metal conduit shall be secured by an proved means at intervals not exceeding ___________ feet and within 12" on each side of every outlet box , junction box, cabinet, or fitting.

4 1/2

You have 120v at the panel and 115v at the load. What is the percentage of voltage drop?

4.17%, (120v-115v=5v), you take the difference which is 5v, and divide it by your original voltage 120v, 5v/120v=.0417, 4.17%

All equipment located within _________ feet of the inside wall of a pool shall be grounded.

5

Two 120 volt light bulbs connected in series across 240 volts will _____. A) burn at full brightness, b) burn at half- brightness, c) burn out quickly, d)flicker with the cycle

A) burn at full brightness, Because the lights have a fix resistance and the voltage is doubled, so there's no voltage drop. But the bulbs will burn out shortly afterward, but not quickly.

At leading power factor, the armature flux of an alternator ________ the rotor flux.

Aids

Operation of equipment in excess of normal, full-load rating, or of a conductor in excess of a rated capacity which, when it persists for a sufficient length of time, would cause damage or dangerous overheating is called __________.

An overload

The cord on a heating iron would most likely have an insulation of ____________.

Asbestos

A _______ is a typical type of thermostat used in appliances with heating elements.

Bimetallic

A repulsion - start induction - run single - phase motor runs as an induction only when ________.

Commutator segments are short-circuited

Autotransformers used to start large induction motors are frequently called a starting ________.

Compensator

The reciprocal of resistance is ________.

Conductance

Encased with a material or composition or thickness that is not recognized by the code as electrical insulation is defined as a covered ______.

Conductor

A capacitor consists of ________.

Conductors separated by a dielectric

A________ is a device which serves to govern in some predetermined manner the electric power delivered to the apparatus to which it is connected.

Controller

The basic unit of electric charge is the________.

Coulomb

A grounding conductor installed over lightning cables for the purpose of interconnecting the system ground electrodes and providing lightning protection for the cables is called a/an ______.

Counterpoise

A galvanometer is used to indicate ______.

Current

The main disadvantage of a low power factor is that __________.

Current required for a given load, power is higher

If the starting winding of a single-phase induction motor is left in the circuit, it will ________.

Draw excessive current and overheat

The switch with the fastest speed of operation is a/an __________ switch.

Electronic

Electrical current is measured in terms of ______.

Electrons passing a point per second

For better illumination you would use _______.

Even spacing, numerous lights

It is good practice to use ____________ in a long horizontal straight run of conduit.

Expansion

An outlet box should be fastened to a solid concrete wall by means of __________.

Expansion bolts

What does a shunt for a milliammeter do __________?

Extends the range and reduces the meter resistance

_________ is a disruptive discharge between electrodes of a measuring gap, voltage gap or protective device.

Flashover

The lead covering on conductors is used_________.

For moisture proofing

A branch-circuit that supplies a number of outlets for lighting and appliances is known as a _______ branch-circuit.

General purpose

The conductor used to connect the grounded circuit of a wiring system to a grounding electrode is the ________.

Grounding conductor

A pendant fixture is a _________.

Hanging fixture

The words "thermally protected" appearing on the nameplate of a motor indicates that the motor is provided with a _____.

Heat sensing element

Inverse-time characteristics of a circuit breaker means __________

Higher fault current, shorter time needed to trip

An insulated conductor with a white or gray finish shall be permitted as _________ or _______ conductor where permanently reidentified to indicate its use, by painting or other effective means at its termination and at each location where the conductor is visible and accessible

Hot or ungrounded

A ______ is used for testing specific gravity.

Hydrometer

A surge of unidirectional polarity is called _________.

Impulse

True Power is always voltage times current in a __________ circuit.

In a DC circuit

Wound rotor and squirrel cage are two types of _________ motors.

Induction

The resistance of a component having no continuity is ________.

Infinite resistance

An open coil has ______.

Infinite resistance and zero inductance

Sparking between contacts can be reduced by _________.

Inserting a capacitor in parallel with the contacts

The ampacity of a solid or stranded conductor of the same material is the same if it has the same _________.

Insulation

Overcurrent devices shall not be connected in series with any conductor that is ______.

Intentionally grounded

A contact connected in a control circuit that will ensure that a particular sequence of operation is followed is called a/an _______.

Interlock

Define shunt

Is a device which creates a low-resistance path for electric current, to allow it to pass around another point in the circuit. Used to measure current, alternating or direct. , one way a shunt is used is in a ammeter.

Define Power Factor

Is the ratio of the real power that is used to do work

Define apparent power

Is when the circuit has inductance or capacitance,and the current or voltage is out of phase. The volt-amps is more then power in watts.

The reason why alternating current can induce voltage is_________.

It has a varying magnetic field

When a stationary three - phase induction motor is switched on with one phase disconnected _______.

It is likely to burn out quickly unless disconnected immediately

____________ is a term used to express the amount of electrical energy in an electrostatic field.

Joules

A _______ is used to maintain the strength of a magnetic field.

Keeper

__________ may be connected ahead of the main service switch.

Lightning arresters - a device for providing a path by which lightning disturbances or other static discharges are passed to earth.

Metal cabinets used for lighting circuit are grounded in order to _________or ______.

Limit the voltage to ground or facilitate overcurrent device operation

The power factor of an alternator is determined by its________.

Load

Incandescent light bulbs when operated at a voltage less than the rated voltage, will normally result in ________.

Longer bulb life

A plug fuse contains a safety element composed of a piece of metal that has a ____________.

Low resistance and low melting point

The force which sets up or tends to set up magnetic flux in a magnet is _______force.

Magnetomotive

Receptacle outlets in a residence shall be installed so that no point along the floor line in any wall space is ______,measured horizontally, from an outlet in that space.

More than 6'

To find the circular - mil area of a stranded conductor, the most accurate method is to________.

Multiply the number of strands by the circular - mil area of one strand

In motor controls, a maintaining contact is a _________contact.

Normally open

Three conductors ( phase A, B and neutral) run from a busway to a load center should not be installed in three separate raceways because ________.

Of inductance

The essential condition for parallel operation of two single phase transformers is that they should have the same __________.

Polarity

When the power factor of a circuit is zero the __________.

Power absorbeb is zero

If there are no overcurrent protective devices rated 30 amps or less with neutral connection, the panel board is classified as a _______.

Power panelboard

What winding of a current transformer will carry more current?

Primary

The symbol that is expressing the power factor is _________.

R/Z

DC voltage is reduced with a _____________.

Resistor

The property of magnetic materials of retaining magnetism after withdrawal of the magnetizing force is referred to as _______.

Retentivity

The_______ is the service conductors between the terminals of the service equipment and a point usually outside the building, clear of building walls, where joined by tap or splice to the service drop.

Service entrance conductors, overhead system

Relay contacts are made of ___________.

Silver

Grounding conductor shall not be connected by_______.

Soldered fittings

A transformer core is made of_________.

Steel

New brushes for a generator should be fitted to the commutator by using a ________.

Strip of sandpaper

D.P.D.T. Letters would be used to identify a

Switch

An electric motor in which the rotor and stator fields rotate with the same speed is called a/an ________.

Synchronous

The air space between the poles of a magnet is called_________.

The air gap

Define keeper

The armature of a magnet; the bar of soft iron placed across the poles of a horseshoe magnet to prevent loss of magnetism.

The voltage of a circuit is best defined as ______.

The effective difference of potential between two conductors

If the clips on a cartridge fuse become hot, this is a good indication that___________.

The fuse clips are too loose

Defined apparatus

The organization or system used for doing or operating something

Define True Power

This is when a AC circuit contains only resistance, and the circuits voltage and current is in phase.

Defined facilitate

To make something easier

Transformers are rated in kva instead of kw because_______.

Total transformer lose depends on va

If a transformer bank is using an open delta connection, ________ single - phase transformers are interconnected

Two

A overcurrent trip unit of a circuit breaker shall be connected in series with each _____.

Ungrounded conductor

In a 2-wire, 120v circuit, the black wire (hot) is a _______ conductor and the white wire is a ______ conductor.

Ungrounded, grounded

The proper way to mount an instrument meter is to ______.

Use a template

________ is equipment which utilizes electric energy for mechanical, chemical, heating, lighting, or similar purposes.

Utilization equipment

The load in an electrical circuit is used to _______.

Utilize the electrical energy

If the power factor of a circuit is unity, its reactive power is__________.

Zero

The ideal internal resistance of an ammeter should be __________.

Zero

XC

______ is the letter(s) used to indicate capacitive reactance in a circuit. A) XL, B) Z, C) HZ, D) XC