Suppose a free electron in air is 1.3 cmcm away from a point charge. What minimum charge is needed to cause a breakdown and a spark as the electron moves toward the point charge?

C

Explanation:

In order to cause a breakdown and a spark the electric field should be at least

E =

We know that

a free electron in air is r = 1.3 cm away from a point charge.

therefore,

substituting the values we get

= C

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