Every person elected by the people or appointed to any city office shall, before entering upon the duties of the office, take and subscribe the oath of office prescribed in Article VI, § 7 of the Constitution. Oaths of office shall be administered by some person authorized by law to administer oaths, and shall be filed with the city clerk. (R.C., c. 111, s. 12; Code, s. 3799; Rev., s. 2920; C.S.,  s. 2628; 1971, c. 698, s. 1.)