Measurement
Electro-mechanical Instruments
Practice questions from Electro-mechanical Instruments.
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IncorrectInstrument(s) required to synchronize an alternator to the grid is/are
The correct answer is option (a) Voltmeter and (c) synchroscope.
Voltmeter: It is used to measure the voltage of the alternator and ensure it matches the grid voltage before synchronization.
Synchroscope: It helps to match the phase angle and speed of the alternator with the grid's frequency before connecting it.
In the coordinate system, three point-charges , and are located in free space at , and , respectively. The value of for the electric field to be zero at is ________(rounded off to 1 decimal place).
For net to be zero at ,
A 3-phase, star-connected, balanced load is supplied from a 3-phase, (rms), balanced voltage source with phase sequence R-Y-B, as shown in the figure. If the wattmeter reading is and the line current is (rms), then the power factor of the load per phase is
Wattmeter is connected such that current coil lies in one phase & potential coil is connected across other 2 phases.
Reading of wattmeter = VLIL sinφ
-400 = 400 × 2 × sinφ
φ = -30°
Since φ < 0, pf is leading
pf = cos 30° = 0.866 leading