Measurement Part Three

Measurement Part Three

1.A torque is developed in an electro mechanical energy conversion device, the value of which depends upon
(a) stator field strength and torque angle
(b) stator field and rotor field strength
(c) stator field and rotor field strengths and the torque angle
(d) stator field strength only

Answer-C

2………………instrument is from hysteresis and eddy current errors.
(a) Electrostatics
(b) Moving Iron
(c) Moving coil-Permanent Magnet type
(d) Moving coil dynamometer type

Answer-A

3. Moving iron instruments can be used
(a) To measure dc currents only
(b) To measure ac currents only
(c) To measure a.c. voltage only
(d) To measure a.c. and d.c. currents and voltage

Answer-D

4.Moving coil instrument, having coil resistance of 4.5Ω gives a full scale deflection of 30 mA. The resistance connected in parallel with this instrument to read up to 2.5A is
(a) 6.46Ω
(b) 0.0346Ω
(c) 0.0546Ω
(d) 0.0625Ω

Answer-C

5. In a particular meter, the operating torque is directly proportional to the current passing through it, then the type of meter is
(a) Moving iron
(b) Moving coil
(c) Electrostatic
(d) Induction

Answer-B

6.In inducting instruments the springs are mainly used to
(a) Conduct the current to the coils
(b) Hold the pivot in position
(c) Control the pointer movement
(d) Reduce the vibration of the pointer

Answer-C

7. To maximize the driving torque in an induction type instrument, flux produced by shunt coil and series coil should be
(a) In phase with each other
(b) In quadrature with each other
(c) Displaced by 45º with respect to each other
(d) Out of phase with respect to each other

Answer-B

8.What is a Weston frequency meter?
(a) Moving coil instrument
(b) Moving iron instrument
(c) Dynamometer type instrument
(d) none of these

Answer-B

9. Indicating instruments should be
(a) Undamped
(b) Critical damped
(c) Over damped
(d) Under damped

Answer-B

10. The effect of stray magnetic fields on the actuating torque of a portable instrument is the maximum when the operating field of the instrument and the stray fields are
(a) Perpendicular
(b) Parallel
(c) Inclined at 60º
(d) Inclined at 30º

Answer-B

11. A moving iron instrument can be used for current and voltage measurements?
(a) In AC circuit only
(b) In DC circuits only
(c) In both AC and DC circuit
(d) None of these

Answer-C

12.The controlling torque in power factor meter is given by
(a) Spring control
(b) Sensor control
(c) Gravity control
(d) None of these

Answer-D

13. A 0-1 mA PMMC ammeter reads 4 mA in circuits. Its bottom control spring snaps suddenly. The meter will now read nearly
(a) Zero
(b) 10 mA
(c) 2 mA
(d) 8 mA

Answer-A

14. Following is not an advantage of a permanent magnet moving coil instrument
(a) It has a uniform scale
(b) It can be used without error for a long period of time
(c) It has good damping torque
(d) Its range can be easily extended

Answer-B

15. Energy savings potential of variable torque application compared to constant torque application is
(a) Higher
(b) Minor
(c) Equivalent
(d) None of the above

Answer-B

16. Determine the absolute error of measurement if measured value of a resistance = 20.65Ω and true value = 20.55Ω.
(a) 0.1Ω
(b) 0.2Ω
(c) 0.3Ω
(d) 0.4Ω

Answer-A

17. The most efficient form of damping employed in electric instruments is
(a) Air friction damping
(b) Fluid friction damping                               
(c) Eddy current daming
(d) None of the above

Answer-C

18. The moving system of an indicating type of electrical instrument is subjected to
(a) a deflecting torque
(b) a controlling torque
(c) a damping torque
(d) All of the above

Answer-D

19. The type of instruments used mainly for standardizing instruments in laboratories is
(a) Indicating instrument
(b) Integrating instrument
(c) Absolute instrument
(d) Recording instrument

Answer-C

20. Which torque is essential for indicating instruments
(a) Deflecting
(b) Controlling
(c) Damping
(d) All of the above

Answer-D