Sparks occur when the electric field in air exceeds 3 x 106 N/C. This is because

Question

Sparks occur when the electric field in air exceeds 3 x 106 N/C. This is because free electrons normally present in air are accelerated to such high speeds that their kinetic energy will overcome the potential energy holding other electrons to atoms. When those electrons rearrange themselves after such a collision, a flash of light is emitted. Let us suppose that the work done on an electron must give it an energy of 3 x 10-19 J to cause this ionization. How far does an electron involved in making in a spark travel through the air before it collides with an atom?

Explanation / Answer

F = q*E
= (1.6*10^-19)* (3*10^6) N

Now,
Work,
W = F*d
3*10^-19 = (1.6*10^-19)* (3*10^6) * d
d = 6.25*10^-7 m
Answer: 6.25*10^-7 m

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