How can we know supply line is ac or dc?

just use a tester .................. :)

thanks for invitation

question is not specific, however in low current wire can be used for AC and DC

if wire connected to device then check name plate of device

We can Know the line is AC by 3 Phases(RST Or 408)

We can Know the line is AC by 2 Phases (+&-)

Sorry but dont know the answer

You can simply check by mutimeter else Ac wires are thick while dc are thin