UTILITIES | Electrical Systems | 10 Questions (EASY)
ELECTRICAL SYSTEMS
(10 Questions, Difficulty Level:EASY)
by Raison John J. Bassig
Q#1: Which among the following lamp holders can fit a bulb with a GU10 lamp base?
(Images of lamp holders courtesy of sinolec.co.uk , leds4less.co.uk , buylightfixtures.com , and lightingsolutions.co.ke)
a. A
b. B
c. C
d. D
The appropriate bulbs for the above given lamp holders are as follows:
(Images of lamps courtesy of DHgate.com , caselllighing.com , sunsetmarin.com , and lampco.co.uk)
Edison lamps, denoted by the prefix "E" such as E27, E40, E12, E11, etc., have a screw-type base. The numbers are measurements of the diameter of the base (in millimeters), so an E27 has a 27mm diameter base, an E40 has a 40mm diameter base, and so on. The most common size used is the E27 or the E26 (can sometimes be used interchangeably on certain lamp holders due to both only having a 1mm difference). Certain sizes have common trade names such as "Mogul" (for E39 or E40 lamps) and "Candelabra" (for E12).
Some bi-pin lamp bases and holders are denoted by the prefix "G" (some are "GU", "GY", and other variants). In a G5.3 or GU5.3 lamp, the numbers are measurements of the center-to-center distance (in millimeters) between the two pins, in this case, 5.3mm.
Bayonet lamps, denoted by the prefix "BA" (though some are "B", and other variants), are twist-and-lock types featuring a horizontal arm on the sides of the lamp base (non-electrical arm) that is inserted into L-shaped slats on the walls of a lamp holder then rotated and pushed slightly upward on the short vertical serif of the slat to lock the lamp in place.
A special type of bi-pin lamp base is a fusion of the bi-pin with a twist-and-lock (similar to bayonet lamps). An example is the GU10 lamp wherein the two pins (the actual electrical contacts) are inserted into a lamp holder via a pair of arc-shaped slats and rotated in the direction where the slats' have a diminished gap to hold and lock the lamp base in place. As the other bi-pin lamps, the number on a GU10 lamp means that the two pins are 10mm apart.
Therefore, the correct answer is d. D.
Q#2: The main current-carrying winding of a motor or generator in which electromotive force is induced.
a. Core
b. Brush
c. Electric motor
d. Armature
e. Coil
Core:
"A mass of iron or other ferrous material in an electromagnet, induction coil, or transformer, serving to concentrate and intensify the magnetic field resulting from a currunt in a surrounding coil."
Brush:
"A copper or carbon conductor serving to maintain electric contact between fixed and moving elements in a motor or generator."
Electric motor:
"A machine that converts electric power into mechanical energy."
Electric motor:
"A machine that converts electric power into mechanical energy."
Armature:
"The main current-carrying winding of a motor or generator which electromotive force is induced."
(Page 75, A Visual Dictionary of Architecture by Francis D.K. Ching)
Therefore, the correct answer is d. Armature.
Q#3: A device used to convert direct current (DC) to alternating current (AC).
a. Transformer
b. Inverter
c. Rectifier
d. Generator
A TRANSFORMER is for reducing or increasing the voltage (V) of an alternating current (AC).
A RECTIFIER is an electrical device that converts alternating current (AC) to direct current (DC).
A GENERATOR is a device that converts mechanical energy to electrical energy.
An INVERTER is a device that changes direct current (DC) to alternating current (AC).
Therefore, the correct answer is b. Inverter.
Q#4: It is a group of two or more cells connected together to produce electric current.
a. Anode
b. Battery
c. Galvanic Cell
d. Cathode
e. Electrolyte
An ANODE is an electrode through which the conventional current ENTERS into a polarized electrical device.
"The negative terminal of a primary cell or storage battery."
(Page 74, A Visual Dictionary of Architecture by Francis D.K. Ching)
This contrasts with a CATHODE, an electrode through which conventional current LEAVES an electrical device.
"The positive terminal of a primary cell or storage battery."
(Page 74, A Visual Dictionary of Architecture by Francis D.K. Ching)
The direction of conventional current (the flow of positive charges) in a circuit is opposite to the direction of electron flow, so (negatively charged) electrons flow out the anode into the outside circuit. In a galvanic cell, the anode is the electrode at which the oxidation reaction occurs. (https://en.wikipedia.org/wiki/Anode)
Galvanic Cell (or Voltaic Cell), named after Luigi Galvani (or Alessandro Volta), is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell. It generally consists of two different metals immersed in an electrolyte, or of individual half-cells with different metals and their ions in solution connected by a salt bridge or separated by a porous membrane. (https://en.wikipedia.org/wiki/Galvanic_cell)
"A device for converting chemical into electrical energy, usually consisting of a receptacle with electrodes in an electrolyte."
(Page 74, A Visual Dictionary of Architecture by Francis D.K. Ching)
An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. (https://en.wikipedia.org/wiki/Electrolyte)
"A nonmetallic conducting medium in which current is carried by the movement of ions."
(Page 74, A Visual Dictionary of Architecture by Francis D.K. Ching)
When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode.
The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal. When a battery is connected to an external electric load, a redox reaction converts high-energy reactants to lower-energy products, and the free-energy difference is delivered to the external circuit as electrical energy.
Historically the term "battery" specifically referred to a device composed of multiple cells, however the usage has evolved to include devices composed of a single cell. (https://en.wikipedia.org/wiki/Electric_battery)
"A group of two or more cells connected together to produce electric current."
(Page 74, A Visual Dictionary of Architecture by Francis D.K. Ching)
(Page 74, A Visual Dictionary of Architecture by Francis D.K. Ching)
Therefore, the correct answer is b. Battery.
Q#5: In a typical incandescent lamp, identify which part is the Stem Press.
A ==> Filament (Tungsten)
B ==> Support Wires (Molybdenium, no electrical contact)
C ==> Button and Button Rod (Glass)
D ==> Lead-in Wires (Copper and Nickel, carries current)
E ==> Stem Press
Q#6: In specifying insulated conductors for general wiring, what is "TW"?
a. Nylon-jacketed Heat-resistant Thermoplastic Wires
b. Moisture- and Heat-resistant Thermoplastic Wires
c. Moisture- and High Heat-resistant Thermoplastic Wires
d. Thermoset Wires
e. Moisture-resistant Thermoplastic Wires
In the choices above,
Choice a.) ==> "THHN"
Choice b.) ==> "THHW" or "THW"
Choice c.) ==> "THWN-2"
Choice d.) ==> "SIS"
Choice e.) ==> "TW"
(Table 3.10.1.13 of the Philippine Electrical Code)
Therefore, the correct answer is e. Moisture-resistant Thermoplastic Wires.
Q#7: Which of the following precludes Electrical Regulations regarding clearance of service drops?
No parts of swimming pools shall be placed under existing service-drop conductors or any other overhead wiring
No service-drop conductors or any other overhead wiring shall be installed above observation stands
Service drop of communication lines, when crossing a street, shall have a minimum clearance of 5.50 meters from the crown of the street or sidewalk over which it passes
No service-drop conductors or any other overhead wiring shall be installed above swimming pools and its area extending 2.00 meters outward horizontally from the inside of the walls of the pool
Conductors shall have a horizontal clearance of not less than 1.00 meter from windows, doors, porches, fire escapes, or similar locations and shall be run at least 500 mm above the top level of a window or opening
According to the 2004 Implementing Rules and Regulations (IRR) of the National Building Code of the Philippines (PD 1096) under Electrical Regulations on Clearance of Service Drops,
"Service drop conductors shall not be readily accessible and when not in excess of 600 volts, shall conform to the following:
Conductors shall have a clearance of not less than 2.50 meters from the highest point of roofs over which they pass with the following exceptions:
(a) Where the voltage between conductors does not exceed 300 volts and the roof has a slope of not less than 100 millimeters in 300 millimeters, the clearance may not be less than 1.00 meter.
(b) Service drop conductors of 300 volts or less which do not pass over other than a maximum of 1.20 meters of the overhang portion of the roof for the purpose of terminating at a through-the-roof service raceway or approved support may be maintained at a minimum of 500 millimeters from any portion of the roof over which they pass.
Conductors shall have a clearance of not less than 3.00 meters from the ground or from any platform or projection from when they might be reached.
Conductors shall have a horizontal clearance of not less than 1.00 meter from windows, doors, porches, fire escapes, or similar locations and shall be run less than 1.00 meter above the top level of a window or opening.
Service drop of conductors, when crossing a street, shall have a clearance of not less than 5.50 meters from the crown of the street or sidewalk over which it passes; and shall have a minimum clearance of 3.00 meters above ground at its point of aattachment to the building or pedestal.
No parts of swimming and wading pools shall be placed under existing service drop conductors or any other overhead wiring; nor shall such wiring be installed above the following:
Swimming and wading pools and the area extending 3.00 meters outward horizontally from the inside of the walls of the pool;
Diving structures;
Observation stands, towers or platforms."
(Rule XIII, Sec. 1301.5 of the 2004 IRR of PD 1096)
Therefore, the correct answer is d. No service-drop conductors or any other overhead wiring shall be installed above swimming pools and its area extending 2.00 meters outward horizontally from the inside of the walls of the pool (this PRECLUDES the Code as "2.00 meters" should have been "3.00 meters").
Q#8: An open metal framework for supporting insulated electrical conductors.
a. Cable tray
b. Raceway
c. Surface raceway
d. Busway
e. Duct
Raceway:
"A channel expressely designed to hold and protect electric wires and cables."
Surface raceway:
"A raceway designed for exposed installation in dry, nonhazardous, noncorrosive locations."
Bus duct (or busway):
"A rigid metal housing for a group of buses insulated from each other. Also called busway."
Duct:
"An enclosed runway for housing conductors or cables."
Cable tray:
"An open metal framework for supporting insulated electrical conductors."
(Page 78, A Visual Dictionary of Architecture by Francis D.K. Ching)
Therefore, the correct answer is a. Cable tray.
Q#9: A three-phase circuit is energized by alternating currents or voltages differing in phase by how much?
a. 360°
b. 120°
c. 90°
d. 180°
e. 22.5°
Single-phase ==> 180° difference
Two-phase ==> 90° difference between phases
Three-phase ==> 120° difference between phases
Therefore, the correct answer is b. 120°.
Q#10: Electric cable consisting of two or more insulated conductors enclosed in a nonmetallic, moisture-resistant, flame-retardant casing.
a. Romex cable
b. BX cable
c. Mineral-insulated cable
d. Shielded cable
e. Armored cable
Among the choices, only a. Romex cable has a nonmetallic enclosure while the rest all have metallic sheathing.
Armored cable (or BX cable):
"Electric cable consisting of two or more insulated conductors protected by a flexible, helically wound metal wrapping. Also called BX cable."
Mineral-insulated cable:
"Electric cable consisting of a tubular copper sheath containing one or more conductors embedded in a highly compressed, insulating refractory mineral."
Shielded cable:
"An electric cable enclosed within a metallic sheath in order to reduce the effects of external electric or magnetic fields."
Nonmetallic sheathed cable (or Romex cable):
"Electric cable consisting of two or more insulated conductors enclosed in a nonmetallic, moisture-resistant, flame-retardant sheath. Also called Romex cable."
(Page 78, A Visual Dictionary of Architecture by Francis D.K. Ching)
Therefore, the correct answer is a. Romex cable (or Nonmetallic sheathed cable).
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