Electrical and ...

In a particular test, the readings of two wattmeters are 5 kW and 1 kW. If the second-meter connections reversed, the total power and power factor are

5 A, 230 V electrodynamic type wattmeter has a scale having 100 divisions. The current coil carries a current of √2 cos (314 πt) A. The voltage across the pressure coil is √2 × 200 sin (314 πt) V. The needle of wattmeter will move by how many divisions _____ (in integer)

A voltage, 80 sin ωt + 60 sin (3ωt – 60°) + 5 sin (5ωt + 30°) V is applied to pressure coil circuit of a wattmeter and through the current coil a current of 12 sin ωt + 8 cos (5ωt + 90°) is passed, the reading of wattmeter will be _______ watt.

A wattmeter is measuring the power supplied to a circuit whose power factor is 0.5. The frequency of the supply is 50 c/s. (cycle/seconds). The wattmeter has a potential coil circuit of resistance 1000 Ω and inductance 0.5 H. The error in the meter reading is ______ %

A 300 V, 20 A dynamometer instrument is used as a wattmeter. Its current coil has 0.2 Ω resistance and pressure coil has 20 kΩ resistance with negligible inductance. What is the error in the instrument if it is used to measure the power in a circuit with supply voltage of 300 V, load current of 16 A at 0.4 pf. Assume that the pressure coil is connected across load side.

 A three-phase balanced delta- connected load gives wattmeter readings of 1000 W and 650 W, when the two wattmeter method is applied. If the line voltage is 440 V, the magnitude of impedance (in ohms) in each arm of the load is.