Question

why is spark produces in a circuit by touching two opposite wire​

Answer 1

$\Large{\textsf{\pink{\underline{ANSWER}}}}$

★If the two wires are at different voltage levels, a short circuit is created when they touch each other. That creates the spark.

★When you bring the two wires closer to each other, at one point, the gap is so low that the air between the wires is ionised and it breaks down, allowing a spark between the two surfaces.