281. 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

282. A 35 V dc supply is connected across a resistance of 600 in series with an unknown resistance 111. A voltmeter having a resistance of 1.2 kL2 is connected across 600Q resistance and reads 5V. The value of resistance Rx will be

A. 120 SI

B. 400 S2

C. 1.8 SI

D. 2.4 52

283. 'Creep' in energy meters can be prevented by

A. using extra turns of 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

284. An integrating digital voltmeter measures

A. true average value

B. rmsivalue

C. peak value

D. peak to peak value

285. Which of the following can be considered to be the advantages of Maxwell's inductance-capacitance bridge when compared to other types of bridges? I. Balance equation of real part is independent of that of imaginary part. 2. Frequency terms does not figure in the equation. 3. When balance is achieved, the value of capacitance multiplied by resistances gives the value of inductance. The bridges is capable of measuring 'Q' of coil of a very wide range, that is, from 1 to 200. Select the correct answer using the codes given below :Codes :

A. 1, 2 and 3

B. 1, 3 and 4

C. 1, 2 and 4

D. 2, 3 and 4

286. A voltmeter has a uniform scale with 100 divisions. The full-scale reading is 10 V and could be read upto 1/10 of a scale division with some degree of certainity.It's resolution is

A.0.1 V

B. 0.02 V

C. 0.01 V

D. 0.001 V

287. One of the two wattmeters has read zero in the two-wattmeter method of power measurement. This indicated that the load phase angle is

A. 0?

B. 30?

C. 60?

D. 90?

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