Alternating current circuits and fundamentals

The power supply mainly is of two types 1.Direct current(d.c) 2.Alternating current(a.c)

1. Direct current :  In d.c, currents are steady and in one direction and dc is limited to few applications e.g. traction,batteries,etc.. 

2. Alternating current: 1) in ac,the voltage acting in the circuit changes polarity at regular intervals of time and the resulting current changes the direction. 2) electrical energy is universally generated,transmitted and used in the form of a.c and we can convert ac in to dc by using rectifier and dc to ac by using inverter.

Advantages of alternating current

• alternating voltages can be stepped up or stepped down efficiently by means of transformer
• ac motors are cheaper and simpler in construction than dc motors
• the switch gear for ac system is simpler than dc system.

Sinusoidal alternating voltage and current

alternating voltage is a sine wave. A sinusoidal alternating voltage can be produced by rotating a coil with a constant angular velocity (w) in a uniform magnetic field. e=Em sin(wt) where e is instantaneous value of alternating voltage,Em is maximum value and w angular velocity of the coil. sinusoidal voltages always produce sinusoidal currents. i=Im sin(wt) 

Advantages of sine wave:

• produces least iron and copper losses for a given output. therefore,efficiency is better.
• produces less interference(noise).
• produces least disturbance in the circuit,and is smoothest and efficient waveform