Answer:
The positive and negative wires spark when touched because they form a short circuit, which means that the current flows through the wires without any resistance or load.
This causes a lot of heat and energy to be released, which can create sparks and even fire.
The sparks are also caused by the voltage difference between the wires, which makes the electrons jump across the air gap.
When the wires are connected to an appliance like a bulb, there is some resistance and load in the circuit, which reduces the current and prevents sparks from forming.