A variable reluctance type tachometer has 150 teeth on rotor. The counter records 13500 pulse/sec. The rotational speed is

4800 RPM

5400 RPM

6000 RPM

7200 RPM

Correct Answer : Option (B) : 5400 RPM

Explanation :

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In measurements using strain gauge, the dummy strain gauge is used to

compensate for error in voltmeter

compensate for change in temperature

compensate for resistance of strain gauge

compensate for error due to change in voltage of battery

Correct Answer : compensate for change in temperature

A CT is used to feed current coils of wattmeter, energy meter, power factor meter and an ammeter. Then

all coils are in parallel

the coils are in series-parallel

all the coils are in series

None of the above

Correct Answer : all the coils are in series

A permanent magnet moving coil measures

dc value

peak value

true rms value

rms plus dc value

Correct Answer : dc value