According to one embodiment, a sensor includes a sensor part and a first circuit. The sensor part includes a base body, a fixed electrode fixed to the base body, a supporter fixed to the base body, and a movable part supported by the supporter. The movable part includes a movable region including a movable electrode facing the fixed electrode, and a first support region provided between the movable region and the supporter. The first support region includes a first electrode, and a second electrode insulated from the first electrode. The first circuit is configured to perform a first operation of applying a voltage between the first electrode and the second electrode.