Question

Why closed path is required for the flow of current

Answer 1

Closed path is required for the flow of current so that the current can flow throughout the circuit. If circuit is open, the current cannot flow, because their will be air and air is bad conductor of heat. 

Answer 2

Closed path is required to create potential difference across terminals so that electrons could flow.hence current flows .if circuit would be open the there will be no potential difference