# Recent questions tagged ac

AC power plugs and sockets

AC power

Is the power line voltage available in our homes a dc or an ac voltage?

AC Circuits with Resistance but No Reactance

What is the need of polarity marking in polyphase AC circuits?

Explain how sinusoidal AC voltage is generated by using simple one loop generator.

‘PMMC instrument is not suitable to measure AC quantity’. State the reason.

How range of A.C. ammeter & A.C. voltmeter is extended? Draw suitable diagram.

State any four advantages of A. C. over D. C .

UNIT 1 fundamentals of AC rotating machine Contents 1.1 Introduction 1.2 Advantages 1.3 Parts of AC machines 1.4 Synchronous speed 1.5 AC winding 1.6 Winding factor (Coil pitch and distributed winding) 1.7 Distribution factor 1.8 EMF equation of alternator or generator 1.9 Numericals 1.10 Harmonic 1.11 Slot harmonics 1.12 Harmonics minimization

Draw the waveform of three phase AC supply voltage.

Do you think is DC better than AC to transmit energy?

Write short notes on 3 phase AC system.

Distinguish between AC and DC.

The SCR would be turned OFF by voltage reversal of applied anode-cathode ac supply frequency of A) 10 kHz B) 10 Hz C) 5 kHz D) 5 Hz

An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to secondary turn’s ratio 12:1. The peak inverse voltage is A) 8.62 V B) 12 V C) 19.17 V D) 27.11 V

The main advantage of AC over DC is:  (A) Conversion flexibility from one voltage level to other (B) AC can be easily converted into DC by using a rectifier (C) AC is easy to maintain & can be easily distributed at long distances (D) All of the above

An ac voltmeter using full -wave rectification and having a sinusoidal input has an ac sensitivity equal to  (1) 1.414 times dc sensitivity (2) dc sensitivity (3) 0.9 times dc sensitivity (4) 0.707 times dc sensitivity

The ac bypassing of RF by CF in a common emitter configuration :  (A) increases ac signal across emitter -base junction (B) decreases ac signal across emitter -base junction (C) decreases voltage amplification (D) stabilizes the Q -point

For measurement of radio frequency ac signals __________ type meter is used

An unshielded moving iron voltmeter is used to measure the voltage in an AC circuit. The stray DC magnetic field having a component along the axis will be  (1) unaffected (2) decreased (3) increased (4) either decreased or increased depending on the direction of the DC field

A large AC generator, supplying power to an infinite bus, has a sudden short-circuit occurring at its terminals. Assuming the prime mover input and the voltage behind the transient reactance to remain constant immediately after the fault, acceleration of the generator rotor is

Which of the following motors can run on both AC and DC? A) Universal motor B) Dual wattage motor C) Flexible motor D) All the above

The direction of rotation of an inverter fed 3-phase ac motor is reversed by (A) a mechanical reversing switch (B) reversing the input dc link voltage (C) operating the inverter as a rectifier (D) changing the sequence of switching

In an adjustable speed ac drive which quantity gets reduced above rated speed ? (A) developed torque (B) stator frequency (C) reduced starting torque (D) stator current

Total instantaneous power supplied by a 3-phase ac supply to a balanced R-L load is

An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms?

A parallel AC. circuit in resonance will?

In an A.C. circuit power is dissipated in?

The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is?

In AC. circuits, laminated iron is invariably used in order to?

In an AC. circuit, a low value of kVAR compared with kW indicates?

The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA The power drawn by the circuit is?

Pure inductive circuit takes power from the A.C. line when?

In any A.C. circuit always?

All the rules and laws of D.C. circuit also apply to A.C. circuit containing?

The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of______degrees.

To measure an A. C. voltage by using an A.C. potentiometer, it is desirable that the supply for the potentiometer in taken?