Static Electricity

Introduction

• Static electricity is the build-up of charge on insulating materials.
• It can cause sparks when discharged.

Charge in Materials

• All materials contain charge due to positive protons and negative electrons.
• Normally, charges cancel each other out, making materials neutral.

Charge Build-up

• Friction and Electron Transfer

  • Rubbing materials together (e.g., a bag and a hat) causes friction.
  • Electrons are transferred from one object to another.
  • Conductors (like metals): Electrons move back, preventing charge build-up.
  • Insulators (like polythene rods and cloths): Electrons can't flow back, leading to static charge.

• Example Materials

  • Polythene rod and cloth: Electrons move to the rod, leaving cloth positive.
  • Acetate rod and cloth: Electrons move to the cloth, leaving rod positive.

Key Points on Charge

• Only negative electrons are transferred.
• Positive static charge occurs due to loss of negative electrons, not gain of protons.

Potential Difference and Sparks

• Accumulation of electrons increases charge size.
• Potential difference develops between charged material and the earth (0 volts).
• Electrons can jump the gap if the potential difference is large (sparks).

Charge on Conductors

• Less common than insulators, but possible.
• Example: Cars build up charge due to metal frame contact with wind.
• Discharge occurs as a small spark (e.g., touching a car).

Summary

• Understanding static electricity involves knowing about charge transfer, potential difference, and conditions for discharge.
• Sparks are the result of electron movement due to potential difference.

Conclusion

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