on power line, bird can enjoy sitting from one live wire to the other. However, if a person touches it, then the person will die within split seconds. explain this situation​

Due to potential difference (elaborated in explanation)

Explanation:

When a bird sits on a power line, its whole body is in contact with the power line. It does not have any contact with the ground or anything at a lower potential. Hence, the current does not flow through the bird's body, because there is no potential difference available as a driving force.

Now, when a person touches the power line his hand is at a higher potential provided by the power line, while the rest of his body is connected to the ground, usually through legs. The current always looks for a path from high potential to low potential. Therefore, the body of the person serves as the path for the current. Heavy current flows through the body and the person die within split seconds.