Measurement and Instrumentation
In figure Z1 = 200∠60° ohm. Z2 = 400∠-90° ohm, Z3 = 300∠0° ohm. Then Z4 for bridge to be balanced is

 300∠90° ohm.
 150∠30° ohm.
 600∠-150° ohm.
 400∠-90° ohm.

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Measurement and Instrumentation
For power measurement of three phase circuit by two wattmeter method, when the value of power factor is less than 0.5 lagging

One of the wattmeters will read zero
One of the wattmeter connections will have to be reversed
Both give the same readings
Pressure coil of the wattmeter will become ineffective.

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