Induction electrification

Electrification by induction consists of assigning an electric charge to an object using another charged body without contact between them.

Lightning occurs thanks to the process of induction electrification
To electrify an object by induction means to assign an electric charge to it using another electrified body without contact between them. This electrification process is based on the concept of attraction and repulsion of electrical charges. See in the following diagram how a body is electrified by induction:
  • Initially, there are neutral sphere A and positively charged sphere B. The electrified body (sphere B) is called the inductor, and the neutral body (sphere A) is called the induced.

Initially sphere A is neutral and sphere B is positively charged.

  • Sphere A is brought closer to sphere B. The positive charge on sphere B attracts the negative charges on sphere A and repels the positive ones, causing a separation of charges;

Spheres A and B are brought together and a separation of charges occurs on sphere A

  • Sphere A is connected to earth by a conductor so that the earth’s electrons rise and neutralize the positive charges on that sphere.
  • Sphere A, now negatively charged, is disconnected from earth and separated from the sphere.

Sphere A is detached from the earth and away from sphere B

In the process of electrification by induction, the final electric charge of the conductor that was neutral always has opposite sign to that of the inductor. The same process can be repeated to positively electrify a neutral object, but a negatively charged inductor must be used.

An example of electrification by induction is the occurrence of lightning. When a cloud is electrically charged, it induces charges of opposite signs on the earth’s surface, creating an electric field between the cloud and the surface. If the electric field is very strong, the air can act as a conductor of electricity, causing an electrical discharge.  

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