Every electrical utility shall furnish the Commission in such form and in such detail as the Commission may require all tabulations, computations and other information required by the Commission to carry into effect any of the provisions of this chapter and shall make special answer to all questions submitted by the Commission. Each electrical utility receiving from the Commission any blanks with directions to fill out the same shall cause the same to be properly filled out so as to answer fully and correctly each question propounded therein and it shall return the same to the Commission within the time required. But in case any electrical utility is unable to answer any question it shall so state with good and sufficient reasons therefor. When required by the Commission, each electrical utility shall deliver to the Commission copies of any or all maps, profiles, contracts, franchises, reports, books, accounts, papers and records in its possession or in any way relating to its property or affecting its business and also a complete inventory of its property in such form as the Commission may direct. Each electrical utility shall, when required by the Commission, furnish in such form as the Commission may require all such reports as it may be directed by the Commission to furnish in relation to its operations, property or business, and the Commission may require either periodical or special reports concerning any matter as to which it desires to inquire in order to keep itself informed in the performance of its duties under this chapter. All reports shall be under oath by such officer or officers of the electrical utility as may be required by the Commission.