Any city in this state, which owns and operates any electric light or power plant, may, and is hereby authorized and empowered to, supply electric current from its light or power plant to other municipal corporations for their use and the use of their inhabitants, and also to persons and private corporations for use beyond the corporate limits of such city, and to enter into contracts therefor for such time and upon such terms and under such rules and regulations as may be agreed upon by the contracting parties.