1- If they are connected with the opposite direction means a negative to positive connection, there will be a short circuit
2- If they are connected phase - phase and neutral - neutral .nothing will happens.
If the same line connected each other than nothing will happened, if opposite means negative connect to positive than there will be short circuit. In addition to this, If we connect phase to same phase nothing will happen, but if we connect phase to different phase it lead to short circuit same if we connect phase to neutral. Finally, Same phase nothing happened but different phase short circuit.
