Part - A (Objective test items) -JANUARY - 2009
Q:1. In the figure you will see one type of filament used in incandescent lamps.
a) which type of filament is shown in the figure?
b) What is the material used for the filament?
Ans:1. a) Coiled oil filament. b) Tungsten.
Ans:1. a) Coiled oil filament. b) Tungsten.
Q:2. A 3-phase induction motor driving a planing machine is found to be getting too much hot.
What are the possible reasons for this effect, with respect to supply lines?
Ans:2. 1) Single phasing in the 3 phase supply. 2) Low supply voltage.
Ans:2. 1) Single phasing in the 3 phase supply. 2) Low supply voltage.
Q:3. Wire stripper has a series of sharp openings in its scissors blade to fecilitate stripping of wires
of different sizes.
The correct method of using wire stripper.......
Ans:3. The gauge size og the wire must match with the opening in the wire stripper.
Ans:3. The gauge size og the wire must match with the opening in the wire stripper.
Q:4. In the figure part of a fluorescent lamp circuit is shown.
a) What is the name of this part?
b) How it is connected inltially at the time of starting?
Ans:4. a) starter b) In series with the heating elements.
Ans:4. a) starter b) In series with the heating elements.
Q:5. In electrical insulation work supply to each point is provided through a control switch. Four
methods are generally adopted for this.
Looping out from switch and looping out from switch and ceiling rose are tow such methods.
What are other two methods?
Ans:5. a) Looping out from 3 plate ceiling roses.
b) Looping out from junction boxes.
Q:6. A old resistor has the following colour bands:
1st band : Red ; 2nd band : Green
3rd band : Orange ; 4th band : Gold
Calculate
a) The exact value R (in Ω ) of the resistor.
b) The range of tolerance ∆ R (in Ω from - to).
Ans:6. a) Red Green Orange Gold
2 5 1000 ± 5% ; R= 25,000 Ω with ± 5% tolerance
b) From 23.750 Ω to 26.250 Ω ; 5% of 25,000 Ω = 1250 Ω
Minimum Resistance value = 25,000 Ω - 1250 Ω = 23,750 Ω
Maximum Resistance value = 25,000 Ω + 1250 Ω = 26,250 Ω
Q:7. Domestic mixers / liquidizer generally use universal motor, and it has two windings.
a) What are these windings?
b) How they are connected together?
Ans:7. a) Armature windings are field winding
b) The two windings are connected in series
Q:8. When the machines are coupled, they should be properly aligned.
State tow operations which are to be carried to confirm proper alignment.
Ans:8. a) Levelling off the centre lines of shafts
b) Aligning shafts eliminating radial and axial displacement.
Q:9. In a 3 phase motor one of the phases, which is not connected through NVC of starter, is opened
during running.
What will be the immediate effect on the motor operation?
Ans:9. It will continue to run.
Q:10. In 3 phase 415 v induction motor has 3 terminals for connecting it to supply. Whether the
motor is connected in star or in delta. From the history sheet you get the resistance value
of each phase as 8.5 ohms and the motor is rated for 415 v.
How would you confirm whether the motor is connected in star/delta connection without
dismantling the motor?
Ans:10. By resistance measurement across any two terminals.
If the measured value is 17Ω the motor is star connected.
If the resistance measured value is less than 6Ω the motor is delta connected.
Q:11. There are three basic ways for extinguishing fire.
One way is by cooling (reducing temperature).
Name are the other two tests?
Ans:11. a) By starving the fire by removing fuel.
b) by smoothening ( Isolating fire from supply of oxygen by blanketing)
Q:12. Four tests are conducted before commissioning any electrical appliances.
Insulation resistance test and Earth continuity test are two tests.
What are the other two tests?
Ans:12. a) Continuity test of element. b) continuity test of power cord
Q:13. DC is generated by rotating conductors (armature) in magnetic field.
How dies AC generation differs from DC generation?
Ans:13. AC can be generated either by rotating field or rotating armature.
Q:14. The mixee found to be operating erratic and running at different speed.
How you will solve the problem?
Ans:14. a) check the cord for intermitter break, repair or replace the cord.
b) Check the connection of the socket and plug terminals and tighten them.
c) Check the spring tension brushes and replace the brushes.
d) The switch may be defective, replace the switch.
Q:15. While testing series field and armature winding of a DC compound machine for continuity
with AC supply, you should be careful not to touch shunt field terminals.
why you should not touch shunt field terminals while testing?
Ans:15. Induced voltage due to mutual induction in shunt field gives severe shock.
Q:16. Speed of sling-ring induction motors can be changed by varying rotor resistance.
Due to certain disadvantages this method has limited application.
What are the disadvantages?
Ans: 16. More power loss in Rotor circuit, Power circuit also reduces, Low efficiency.
Q:1. a) state ohms law?
b) what is the power input to an electric heater that draws 3 amp from230 volt supply source ?
c) what is emf? how it can be calculate?
Ans:) see jully 2006 ans no :1a
p) p=230 x3a=690w
the power input to the electric heater is 690w
c) the force which causes current to flow in the circuit is called emf its symbols is E and is measure in volts(V)
=v ate terminal of source3s of supply +voltge drop in the source of supply(or) emf= v+ir
Q:2 .a) state the three essential forces required for an indicating instrument.
b) state the principle of a permanent magnet moving coil (pmmc)instrument.
c) explane the clipping error in an energy meter.
Ansa) the flowing 3 force areessential requirement of an indicating instument for its satisfactryoperation they are
i.deflecting force
ii.controling force
ii.damping force
b) see jully 2008 ans no:2a
c) in som meters the disc rotets continuously
Ans:5. a) Looping out from 3 plate ceiling roses.
b) Looping out from junction boxes.
Q:6. A old resistor has the following colour bands:
1st band : Red ; 2nd band : Green
3rd band : Orange ; 4th band : Gold
Calculate
a) The exact value R (in Ω ) of the resistor.
b) The range of tolerance ∆ R (in Ω from - to).
Ans:6. a) Red Green Orange Gold
2 5 1000 ± 5% ; R= 25,000 Ω with ± 5% tolerance
b) From 23.750 Ω to 26.250 Ω ; 5% of 25,000 Ω = 1250 Ω
Minimum Resistance value = 25,000 Ω - 1250 Ω = 23,750 Ω
Maximum Resistance value = 25,000 Ω + 1250 Ω = 26,250 Ω
Q:7. Domestic mixers / liquidizer generally use universal motor, and it has two windings.
a) What are these windings?
b) How they are connected together?
Ans:7. a) Armature windings are field winding
b) The two windings are connected in series
Q:8. When the machines are coupled, they should be properly aligned.
State tow operations which are to be carried to confirm proper alignment.
Ans:8. a) Levelling off the centre lines of shafts
b) Aligning shafts eliminating radial and axial displacement.
Q:9. In a 3 phase motor one of the phases, which is not connected through NVC of starter, is opened
during running.
What will be the immediate effect on the motor operation?
Ans:9. It will continue to run.
Q:10. In 3 phase 415 v induction motor has 3 terminals for connecting it to supply. Whether the
motor is connected in star or in delta. From the history sheet you get the resistance value
of each phase as 8.5 ohms and the motor is rated for 415 v.
How would you confirm whether the motor is connected in star/delta connection without
dismantling the motor?
Ans:10. By resistance measurement across any two terminals.
If the measured value is 17Ω the motor is star connected.
If the resistance measured value is less than 6Ω the motor is delta connected.
Q:11. There are three basic ways for extinguishing fire.
One way is by cooling (reducing temperature).
Name are the other two tests?
Ans:11. a) By starving the fire by removing fuel.
b) by smoothening ( Isolating fire from supply of oxygen by blanketing)
Q:12. Four tests are conducted before commissioning any electrical appliances.
Insulation resistance test and Earth continuity test are two tests.
What are the other two tests?
Ans:12. a) Continuity test of element. b) continuity test of power cord
Q:13. DC is generated by rotating conductors (armature) in magnetic field.
How dies AC generation differs from DC generation?
Ans:13. AC can be generated either by rotating field or rotating armature.
Q:14. The mixee found to be operating erratic and running at different speed.
How you will solve the problem?
Ans:14. a) check the cord for intermitter break, repair or replace the cord.
b) Check the connection of the socket and plug terminals and tighten them.
c) Check the spring tension brushes and replace the brushes.
d) The switch may be defective, replace the switch.
Q:15. While testing series field and armature winding of a DC compound machine for continuity
with AC supply, you should be careful not to touch shunt field terminals.
why you should not touch shunt field terminals while testing?
Ans:15. Induced voltage due to mutual induction in shunt field gives severe shock.
Q:16. Speed of sling-ring induction motors can be changed by varying rotor resistance.
Due to certain disadvantages this method has limited application.
What are the disadvantages?
Ans: 16. More power loss in Rotor circuit, Power circuit also reduces, Low efficiency.
B- Part - January - 2009
b) what is the power input to an electric heater that draws 3 amp from230 volt supply source ?
c) what is emf? how it can be calculate?
Ans:) see jully 2006 ans no :1a
p) p=230 x3a=690w
the power input to the electric heater is 690w
c) the force which causes current to flow in the circuit is called emf its symbols is E and is measure in volts(V)
=v ate terminal of source3s of supply +voltge drop in the source of supply(or) emf= v+ir
Q:2 .a) state the three essential forces required for an indicating instrument.
b) state the principle of a permanent magnet moving coil (pmmc)instrument.
c) explane the clipping error in an energy meter.
Ansa) the flowing 3 force areessential requirement of an indicating instument for its satisfactryoperation they are
i.deflecting force
ii.controling force
ii.damping force
b) see jully 2008 ans no:2a
c) in som meters the disc rotets continuously
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