a) Has voltage and current coils to measure the real power b) Has three connections two of which are used at a time c) Measures apparent power because the current is same in the voltage and current coils d) Can measure d.c. power but not 60 cps a.c. power Ans: (a)
a) The hysteresis loss can be determined from the area of B-H curve b) Eddy current loss is determined from the area of B-H curve c) Hysteresis and eddy current losses can be determined from the area of the B-H loop d) None of the above losses is determined from the B-M loop Ans: (a)
a) To make the system oscillating b) In order to get first deflection large c) In order to get first deflection small d) To make the system critically damped Ans: (b)
a) Controlling torque is small and damping is heavy b) Controlling torque and damping are large c) Controlling torque is large but damping is small d) Controlling torque and damping are small Ans: (a)
a) True b) False Ans: (a)
a) Electrical resonance frequency meter b) Weston frequency meter c) Heterodyne frequency meter d) Either (b) or (c) Ans: (c)
a) Large working forces b) A scale which extends to 360° c) The absence of ligaments to lead in current to moving coils, all coils in the moving iron types being fixed Ans: ()
a) Weakening of permanent magnets due to ageing and temperature effect b) Weakening of spring due to ageing and temperature effect c) Change of resistance of moving coil with temperature Ans: ()
a) Hysteresis error b) Stray magnetic fields c) Temperature error Ans: ()
a) Frequency errors b) Reactance of instrument coil c) Eddy currents Ans: ()