253. In the two-wattmeter method of measuring power in a balanced three-phase circuit, one wattmeter shows zero and the other positive maximum. The load power factor is
A. zero
B.0.5
C.0.866
D.1

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254. A 35 V dc supply is connceted across a resistance of 600 ohm is series with an unknown resistance R. A voltmeter having a resistance of 1.2 k-ohm is connected across 600 ohm resistance and reads 5V The value of resistance R. will be
A. 120 ohm
B. 1.8 ohm
C. 400 ohm
D. 2.4 k-ohm

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255. 'Creep' is energy meters can be prevented
A. using extra turns on the voltage coil
B. having two holes on opposite sides of the disc.
C. using a stronger brake magnet
D. using steel laminations of high permeability

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256. A0-10 mA PMMC ammeter reads 4 mA in a circuit. Its bottom control spring snaps suddenly. The meter will now read nearly.
A. 10 mA
B. 8 mA
C. 2 mA
D. zero

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257. A Kelvin double bridge is best suited for the measurement of
A. inductance
B. capacitance
C. low resistance (d) high resistance
D.

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258. Type of bridge Application (a) Wien bridge(P) Measurement of resistance (b) Maxwell bridge (Q) High Q inductors (c) Scherring bridge (R) Measurement of frequency (d) Anderson bridge (S) High voltage capacitors (e) Blumleim bridge (T) Low Q inductors (U) Insensitive to stray electrostatic fields
A. a - P, b - U, c - T, d - R, e ? Q
B. a - P, b - T, c - U, d - R, e ? Q
C. a - T, b - P, c - U, d - Q, e ? R
D.

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259. An advantage of a permanent magnet moving coil instrumetn is that it is
A. free from frictino error
B. has high (torque/weight of the moving parts) ratio
C. has low (torque/weight of the moving parts) ratio
D. can used on both a.c. and d.c.

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