Question

When we touch positive and negative potential wires with each other, It give spark. Why?

Answer 1

http://en.wikipedia.org/wiki/Short_circuit
"A common type of short circuit occurs when the positive and negative terminals of a battery are connected with a low-resistance conductor, like a wire. With low resistance in the connection, a high current exists, causing the cell to deliver a large amount of energy in a short time."
\[ P = V I \]

Answer 2

electrons are jumping