Questions & Answers of Measurement of Voltage, Current, Power, Energy and Power Factor

Question No. 164

An energy meter, having meter constant of 1200 revolutions/kWh, makes 20 revolutions in 30 seconds for a constant load. The load, in kW, is _____________.

Question No. 116

A 3-phase balanced load which has a power factor of 0.707 is connected to balanced supply. The power consumed by the load is 5 kW. The power is measured by the two wattmeter method. The readings of the two wattmeters are

Question No. 140

The coils of a wattmeter have resistances 0.01Ω and 1000Ω; their inductances may be neglected. The wattmeter is connected as shown in the figure, to measure the power consumed by a load, which draws 25A at power factor 0.8. The voltage across the load terminals is 30V. The percentage error on the wattmeter reading is _________.

Question No. 29

Power consumed by a balanced 3-phase, 3-wire load is measured by the two wattmeter method. The first wattmeter reads twice that of the second. Then the load impedance angle in radians is

Question No. 130

While measuring power of a three-phase balanced load by the two-wattmeter method, the readings are 100 W and 250 W. The power factor of the load is _________.

Question No. 229

An LPF wattmeter of power factor 0.2 is having three voltage settings 300 V, 150 V and 75 V, and two current settings 5 A and 10 A. The full scale reading is 150. If the wattmeter is used with 150 V voltage setting and 10 A current setting, the multiplying factor of the wattmeter is _________.

Question No. 25

For the circuit shown in the figure, the voltage and current expressions are

vt=E1sinωt+E3sin3ωt and it=I1sinωt-Φ1+I3sin3ωt-Φ3+I5sin5ωt

The average power measured by the Wattmeter is

Question No. 10

Consider the following statement
(i) The compensating coil of a low power factor wattmeter compensates the effect of the impedance of the current coil.
(ii) The compensating coil of a low power factor wattmeter compensates the effect of the impedance of the voltage coil circuit.

Question No. 8

A wattmeter is connected as shown in the figure. The wattmeter reads

Question No. 1

The pressure coil of a dynamometer type wattmeter is

Question No. 48

The figure shows a three-phase delta connected load supplied from a 400V, 50 Hz, 3-phase balanced source. The pressure coil (PC) and current coil (CC) of a wattmeter are connected to the load as shown, with the coil polarities suitably selected to ensure a positive deflection. The wattmeter reading will be