Description : The insulation resistance of a DC motor is observed to be 15 MΩ at a temp. of 70°C. what is its value corrected to 40°C. the correction factor for 70°C is 8.0.
Last Answer : Observed resistance at 70°C – 15 MΩ. Temperature correction factor – 8. Rm = kt * Rt kt – correction factor. Rm = 8 * 15 Rt – resistance measured at +°C. Rm = 120 MΩ. Rm – corrected value to 40°C The IR of DC motor corrected to 40°C is 120 MΩ.
Description : On the meter scale illustrated, while using the R X 100 scale, the reading at 'A' will be ____________. EL-0047 A. 2,000 ohms B. 20 Kohms C. 200 Kohms D. 3 Megohms
Last Answer : Answer: B
Description : An insulation resistance test is performed on a particular piece of electric equipment. In addition to the resistance reading, what information listed below should be entered in the electrical log? A. ... D. The complete nameplate data from the resistance test instrument used to obtain the reading.
Description : Lumirhodopsin is stable only at temperature below (A) –10°C (B) –20°C (C) –40°C (D) –50°C
Last Answer : Answer : D
Description : Fats are solids at (A) 10°C (B) 20°C (C) 30°C (D) 40°C
Last Answer : Answer : B
Description : A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The ... = 283 s (B) t = 356 s (C) t = 400 s (D) t = 800 s
Last Answer : (D) t = 800 s
Description : Thermophilic micro-organism grow well at temperature– 1) 10°C – 20°C 2) 20°C – 40°C 3) 50°C – 60°C 4) 5°C – 7°C
Last Answer : 3) 50°C – 60°C
Description : Which of the following are optimum temperature conditions for making benzenediazonium chloride from aniline? (a) 0°C to 10°C (b) 20°C to 25°C (c) 30°C to 40°C (d) 45°C to 50°C
Last Answer : 0°C to 10°C
Description : If a certain amount of dry ice is mixed with same amount of water at 80°C, the final temperature of mixture will be (a) 80°C (b) 0°C (c) 40°C (d) 20°C (e) 60°C.
Last Answer : Answer : b
Description : If the values of 'C' and 'R' shown in the illustration were 1 microfarad and 3 Megohms respectively, at what listed time would 'C' be considered fully charged? EL-0086 A. 0.33 second B. 3 seconds C. 6 seconds D. 15 seconds
Last Answer : Answer: D
Description : If the values of C and R shown in the illustration were 1-microfarad and 3- Megohms respectively, which of the listed intervals would equal one 'time constant'? EL-0086 A. 0.33 second B. 3 seconds C. 6 seconds D. 15 seconds
Description : When a megohmmeter is being used to test insulation resistance, current leakage along the surface of the insulation is indicated by the megohmmeter pointer _____________. A. fluctuating around a ... slightly downscale as voltage is applied D. continually rising as the test voltage is applied
Last Answer : Answer: C
Description : When troubleshooting motor controllers, a shorted relay or contactor coil is often indicated by _______________. A. a resistance reading of 'infinity' on an ohmmeter B. charred insulation and/or a blown ... of the coil's leads to ground D. a higher-than-normal voltage reading across the winding
Description : When a megohmmeter is being used to test insulation resistance, current leakage along the surface of the insulation is indicated by the megohmmeter's pointer _____________. A. dipping toward ... kicking slightly down scale as voltage is applied D. fluctuating around a constant resistance reading
Description : When using a megohmmeter to test insulation, good insulation will be indicated by _____________. A. slight kicks of the needle down scale B. a downward dip followed by a gradual climb to the true resistance ... C. a gradual rise in the pointer reading at the outset D. the initial dip of the pointer
Description : When a megohmmeter is used to test insulation, the gradual rise of the pointer reading as a result of continued cranking, is caused by _____________. A. good conductor resistance B. the ... insulation C. the inductive reactance of the windings D. the dielectric-absorption effect of the insulation
Description : Before testing insulation with a megohmmeter, the windings of large machines should be grounded for about 15 minutes just prior to the test, because the ___________. A. static charge of the machine ... number of leakage paths C. insulation may be damaged D. insulation may be covered with moisture
Last Answer : Answer: A
Description : If an alternator is to be inactive for a considerable period of time, which of the following actions should be taken? A. It should be disconnected from the prime mover and raised off its bearing supports ... . D. The windings and collector rings should be protected with a thin coat of grease or oil.
Description : When working on electrical circuits containing large capacitors, in addition to deenergizing the circuit, which of the listed precautions should also be taken? A. Keep all radio equipment ... capacitor insulation resistance. C. Ground the capacitor terminals. D. Check capacitor circuit polarity.
Description : In preparing to take insulation resistance readings on a main generator, the windings should be grounded for about 15 minutes prior to the test to _____________. A. allow accurate zeroing of the meter ... the windings D. help the windings to cool to the same temperature as the ground test connection
Description : A Fahrenheit thermometer indicates a temperature of ‘ 14°F. its corresponding reading on the Celsius scale will be -----? A. – 2O°C B. – 10°C (Answer) C. + 10°C D. + 20°C
Last Answer : B. – 10°C (Answer)
Description : An open in the armature of a DC motor is suspected, but is not found by visual inspection of the commutator. The next step in troubleshooting this problem is to ________________. A. conduct a ... windings C. conduct an insulation resistance test of the armature D. test the commutator for a ground
Description : If air gap readings for an electical generating machine have changed significantly from the last reading, you should check _________. A. the bearings B. insulation readings and machine cleanliness C. the prime mover thrust bearing D. the field coil bolts for the proper torque values
Description : 5 days-biochemical oxygen demand (BOD5) is taken at a temperature of A. 0°C B. 15°C C. 20°C D. 25°C
Last Answer : ANS: C
Description : The standard B.O.D. at 20°C, is taken for the consumption in (A) 2 days (B) 3 days (C) 4 days (D) 5 days
Last Answer : (D) 5 days
Description : The capillary rise at 20°C in a clean glass tube of 1 mm bore containing water is approximately (A) 5 mm (B) 10 mm (C) 20 mm (D) 30 mm
Last Answer : Answer: Option D
Description : Electric motors intended for use outside the engine room and boiler room are frequently rated to run at a designed ambient temperature of 40°C. What is the equivalent temperature in degrees Fahrenheit? A. 54.2°F B. 72.0°F C. 104.0°F D. 129.6°F
Description : One item listed on the name plate of a cargo pump motor is 'degrees centigrade rise.' This number is based on _____________. A. normal temperature change from cold to hot B. an ambient temperature ... . minimum heat rise from no load to full load D. maximum degrees centigrade rise from absolute zero
Description : Onion seeds can germinate at a temperature of : a. 0-1°C b. 1-5°C c. 5-11°C d. 15-20°C
Last Answer : 1-5°C
Description : Air gap readings should be taken periodicly on electrical generation equipment to __________. A. determine the amount of varnish that can be applied to correct insulation problems B. determine the ... field coil bolts and correct lateral adjustment of the field coils D. increase machine efficiency
Description : You are performing an out-of-circuit test of the semi-conductor shown in the illustration. Using an ohmmeter on 'low power' position and with leads properly installed, which of the listed results would you expect the ... lead on 'B' and black lead on 'A'; and a low reading with the leads reversed.
Description : A megger is being used to test the insulation of an AC generator. The resistance value of a dry, clean winding will _____________. A. continue to rise as test potential is maintained, ... , becoming fairly steady after 5-7 minutes D. stabilize after approximately 2-4 minutes of fluctuation
Description : You are testing the insulation in an AC generator with a megohmeter. The resistance value of a dry, clean winding will ____________. A. continue to rise as the test potential is maintained, ... fairly steady after 5 to 7 minutes D. stabilize after approximately 2 to 4 minutes of fluctuation
Description : Optimum temperature for cool season vegetables is: a. 25-30°C b. 25-27°C c. 18-24°C d. 15-20°C
Last Answer : 18-24°C
Description : A solid aluminium ball, when quenched in a water bath maintained at 40°C, cools down from 550°C to 450°C in 20 seconds. The expected temperature of the ball after next 20 seconds may be about __________ °C. (A) 370 (B) 340 (C) 320 (D) 300
Last Answer : (A) 370
Description : You are cruising at FL 200, OAT is -40°C, sea level pressure is 1033 hPa. Calculate the true altitude. a. 20,660 ft b. 21,740 ft c. 18,260 ft d. 19, 340 ft
Last Answer : d. 19, 340 ft
Description : Moisture accumulating in electric motors and generator windings having a cold insulation resistance greater than 50,000 ohms may be baked out with internal heat. This heat can be developed by ____________. ... an electric welder and feeding it into the armature while running the motor at full speed
Description : When a megohmmeter is being used on a alternating current machine, the meter pointer will dip toward 'zero' and then gradually rise to the true resistance value if the motor insulation is _____________. A. grounded B. good C. shorted D. dirty
Description : Routine maintenance of dry-type transformers should include ______________. A. preventing the entrance of water from broken pipe lines steam lines B. keeping protective surfaces and insulating bushings free of ... debris C. periodic testing of insulation resistance with a megger D. all of the above
Description : When insulation failure produces a low resistance current path between two conductors, the resulting condition is known as ____________. A. an open B. a short circuit C. a ground D. a surge
Description : A galvanometer is an instrument used to measure ___________. A. thickness of galvanized metal B. resistance of electrical wiring insulation C. very small amounts of current or voltage D. quantity of galvans in an electric circuit
Description : Moisture absorbed in the windings or condensed on the surface of electrical machinery insulation ________. A. is good for long term preserving since most insulation is organic and contains some amount B. ... D. reduces the amount of current supplied or drawn by the machine so horsepower is limited
Description : Which of the instruments listed is used to check insulation resistance? A. Magneto B. Megohmmeter C. Dynamometer D. Rheostat
Description : Before using a volt-ohmmeter to measure resistance readings, you should _____________. A. replace all batteries B. test the insulation resistance of the leads C. make sure the test leads do not touch D. hold the leads together and 'zero' the meter
Description : The existing resistance of a conductor is dependent upon its length, cross-sectional area, _____________. A. temperature and insulation B. material and insulation C. resistive coefficient and material D. material and temperature
Description : When the current flow through a copper wire increases, its _____________. A. resistance will decrease B. insulation will burn C. temperature will increase D. conductivity will increase
Description : During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points
Description : Which of the listed statements is correct when using an analog multimeter as an ohmmeter? A. The pointer should be adjusted to zero each time a new resistance range is selected. B. The ... C. Ohmmeters are not sufficiently sized to measure conductor insulation resistance. D. All of the above.
Description : To carry out an insulation resistance test, one terminal of the megohmmeter should be connected to the winding, with the other terminal being connected to the ____________________. A. power supply B. variable resistor C. frame of the machine D. armature