# ac fundamentals pdf

(b) rises to 38.6% of its final steady value Q.78. Ans: b, 90.
Ans: a, 80. (d) 16 kVAR (a) current (b) 0.707 Emax By incorporating a simple brake and increasing the starting torque, it is possible to switch the direction of motor rotation instantaneously. All books are in clear copy here, and all files are secure so don't worry about it. Ans: c, 37. The period of a sine wave is _____ seconds. (c) volt-amperes Overview of AC Motors. A pure capacitor connected across an A.C. voltage consumed 50 W. This is due to, (c) the size of the capacitor being quite big, Multiple Choice Questions(MCQ) on Magnetism. Ans: d, 49. The phosphors for which of the following pair are 180° out of phase for VL, VC and VR? (d) non-oscillating At very low frequencies a series R-C circuit behaves as almost purely Ans: a, 2. All books are in clear copy here, and all files are secure so don't worry about it. For a single-phase motor, connect the capacitor between the power supply and the motor. (c) power All Rights Reserved. (c) directly as the permeability of the core (a) 200 Hz The r.m.s. Fleming's Right Hand Rule indicates the direction of induced current (for generators) when a conductor is passed through lines of magnetic ﬂux.

AC circuit fundamentals are covered including inductive and capacitive circuits. Ans: a, 35. What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value ?

AC motors generate "magnetic ﬂux" and "induced current" inside the motor by the actions of the stator and the rotor, and obtain rotational force. value of 220 V is induced.

(b) does not take power at all from a line

(a) current is maximum (b) 0.707 of peak value (b) the extent of neutralisation of reactive power in a circuit (a) 100 n

Arago’s disk is the phenomenon when a magnet is moved along the surface of a metal disk, the disk rotates to follow the magnet. Reversible motors are ideal for applications where bidirectional operation is repeated frequently. (d) none of the above (b) results in more power losses in the electrical system (a) consumes some power on average (a) current lags behind the voltage by 90° The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA (b) exchange of power takes place between inductor and supply line Ans: c, 82. (c) unity power factor (a) The current through each element is same (b) both waves must have identical peak values (d) high Ans: b, 81. When operating with a single-phase power supply, we use a phase advancing capacitor to generate a waveform close to a two-phase power supply and generate a rotating magnetic ﬁeld. (c) at the time of turning on and off 90 degree out of phase with the current c. 180 degree out of phase with the current Awesome sir, kindly send me MCQ,s on me email id, i will be very thankful to you for this kindness. The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. (d) 25 mA

(d) current is in phase with the voltage In the case of an unsymmetrical alternating current the average value must always be taken over (a) unsymmetrical part of the wave form, 13. (d) the number of electrons passing through a point in one second Ans: b, 13. Ans: a, 11. (6) will change the resonance frequency For the same peak value which of the following wave will ‘have the highest r.m.s. (b) 50% of maximum value (a) the current through the resistance is more (a) oscillating (c) RC After completing this chapter you should be able to: Develop a familiarity with sinusoidal functions.