Skip to content
CalibratePhysics

13.1

Introduction

AC Circuits · Maharashtra HSC

Theory

13.1 Introduction

There are two kinds of electrical supply. In DC — direct current — the polarity of the voltage is fixed: the positive and the negative ends of the power supply do not change. In AC — alternating current — the polarity of the voltage keeps changing periodically.

Electricity is supplied mostly as AC, because AC is cheap to generate and convenient to transport over long distances. Some appliances such as TV sets, computers and radios first convert AC to DC using a rectifier, while many domestic devices — fans, fridges, air conditioners, induction heaters and coil heaters — run directly on AC and use components such as inductors and capacitors.

The chapter therefore studies the passage of AC through resistors, inductors and capacitors, singly and in series combination, and the consequences: reactance, impedance, power, resonance and the choke coil.

Remember This

  • An AC shock is attractive while a DC shock is repulsive, so 220 V AC is more dangerous than 220 V DC.
  • 220 V AC is an rms value; its peak is e0=±2 erms=±1.414×220≈±311e_0 = \pm\sqrt2\,e_{rms} = \pm1.414\times220 \approx \pm311 V, whereas 220 V DC has a fixed value of 220 V only.