Ac Circuits - Introduction

AC CIRCUITS - INTRODUCTION

Uptill now we have analysed and studied the performance of DC supply and DC circuits. But 90% of electrical energy used now a days is a.c in nature. Electrical supply used for commercial purpose is alternating. The d.c supply has constant magnitude with respect to time.

The use of DC is limited to a few application like:

→ Electroplating

→ Electric traction

→ Charging of batteries

→ Electronic circuits etc. 

Alternating Current

An Alternating Current (a.c) is the current which changes periodically both in magnitude and direction.

AC Waveforms:

The waveforms of most alternating currents represents gradual changes in voltage and current i.e., first increasing in one direction upto a maximum value and decreases to zero. Then it increases in other direction (opposite) upto the maximum value.

Various types of alternating waveforms along with sinusoidal are shown in the Figure 1.20(a), (b), (c), (d).

Advantages of AC Supply:

1. The voltages in AC supply can be raised or lowered with the help of a device called transformer. But in dc supply this is not possible.

2. When the high voltage is transmitted in the transmission line, the current will be minimum. Hence the 1²R loss in the conductor will be minimum and therefore transmission system will be efficient and economical.

3. A.C electrical motors are simple in construction, are cheaper and require less attention from maintenance point of view.

4. Whenever it is necessary ac supply can be easily connected to obtain dc supply. 1.9