NCERT Book Class 12 Physics Chapter 1 Electric Charges and Fields

Chapter One

ELECTRIC CHARGES
AND FIELDS

1.1 INTRODUCTION
All of us have the experience of seeing a spark or hearing a crackle when
we take off our synthetic clothes or sweater, particularly in dry weather.
Have you ever tried to find any explanation for this phenomenon? Another
common example of electric discharge is the lightning that we see in the
sky during thunderstorms. We also experience a sensation of an electric
shock either while opening the door of a car or holding the iron bar of a
bus after sliding from our seat. The reason for these experiences is
discharge of electric charges through our body, which were accumulated
due to rubbing of insulating surfaces. You might have also heard that
this is due to generation of static electricity. This is precisely the topic we
are going to discuss in this and the next chapter. Static means anything
that does not move or change with time. Electrostatics deals with
the study of forces, fields and potentials arising from
static charges.

1.2 ELECTRIC CHARGE
Historically the credit of discovery of the fact that amber rubbed with
wool or silk cloth attracts light objects goes to Thales of Miletus, Greece,
around 600 BC. The name electricity is coined from the Greek word