Electric Charges and Fields — Chapter 1 (Pages 1–2)

1.1 INTRODUCTION

• Everyday observations that hint at electrostatics:

  • Sparks or crackling sounds when removing synthetic clothes (e.g.
    polyester sarees) in dry weather.

  • Lightning flashes during thunderstorms.

  • Small electric shocks when touching car doors, metal hand-rails, or bus bars after sliding off the seat.

• Underlying cause in all cases:

  • Insulating (non-conducting) materials rub against each other and accumulate electric charge.

  • When an oppositely charged or grounded object (including the human body) approaches, the stored charge discharges—producing a spark, light, sound, or a mild shock.

• Key term:

  • Static electricity = electric charge that remains localized (does not flow continuously).

• Field of study:

  • Electrostatics deals with forces, electric fields, and electric potentials produced by static (time-independent) charges.

1.2 ELECTRIC CHARGE

• Historical note:

  • Around 600 BC, Thales of Miletus (Greece) observed that amber rubbed with wool or silk attracts light objects (e.g.
    bits of straw).

  • The word electricity originates from the Greek word for amber.

• Significance:

  • This ancient experiment marks the earliest recorded evidence that rubbing certain materials can create an attractive force—later understood to be the result of accumulated electric charge.

  • Sets the foundation for the modern concept of electric charge and the branch of physics called electrostatics.