Why It Matters | Do you feel a small shock when you touch a metallic surface?

Multiple-arc electrical discharge from a Wimshurst generator.

Multiple-arc electrical discharge from a Wimshurst generator.
| Photo Credit: scotspencer/Getty Images

What are the facts? There have been stray reports from different parts of India of commuters experiencing a small electric shock when they touch metallic surfaces in public. People have also reported feeling such shocks when handling certain materials and fabrics, like nylon and polyester, plastic, and wool.

What is the context?

  • Static shocks are technically called electrostatic discharges.
  • The ‘shock’ is the product of the transfer of electrons from one material to another, because they have different electrical permittivity.
  • Imagine the electrons to be people crowding at a door. If a material’s permittivity is low, it means the door won’t open and let people in.
  • A material with higher permittivity is like the door being wide open. When the electrons encounter such a material, they jump across.

Why does it matter?

  • Electrostatic discharge happens when electric charge (usually electrons) has accumulated somewhere.
  • If it happens when you touch metallic surfaces in public, such as railings or lampposts, it’s because these entities haven’t been grounded properly.
  • In wet weather, the moisture that collects on the surfaces of objects conducts the electrons away.
  • But in drier weather, without the moisture, improperly grounded objects can accumulate small charges on the surface.
  • Static shocks are limited to a minor discomfort as long as the exposure duration (a fraction of a second) and the amount of current transferred are both small.

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