Ted Bettencourt will be sworn in as the new mayor at the city’s inauguration ceremony at 7 p.m. tomorrow in the Wiggin Auditorium in City Hall. Bettencourt, a lawyer and councilor at large, was elected in November to succeed retiring mayor Michael J. Bonfanti. Also taking their oaths will be those elected to fill the 11 City Council seats, as well as three School Committee seats, three Municipal Lighting Commission seats, and five library trustee seats. Bettencourt, who becomes Peabody’s third mayor in more than three decades, will deliver an inaugural speech. Following the ceremony, the City Council and the School Committee will hold brief reorganization meetings to elect their leaders for 2012. - John Laidler