Abstract: A heater includes: a substrate including metal and having a shape extending in one direction; a first insulating part provided on a first surface of the substrate; a first heating element provided on the first insulating part and extending along a longitudinal direction of the substrate; a first protection part provided on the first insulating part and covering the first heating element; a second insulating part provided on a second surface of the substrate facing the first surface; a second heating element provided on the second insulating part and extending along the longitudinal direction of the substrate; and a second protection part provided on the second insulating part and covering the second heating element. A length of the second heating element is different from a length of the first heating element in the longitudinal direction of the substrate.

Abstract: Provided is a heater including: a substrate that has electrical conductivity; a first insulation portion that is provided on a first surface of the substrate, has an insulation property; at least one heat generation body that is provided on the first insulation portion; a second insulation portion that is provided on a second surface of the substrate which is opposite to the first surface, has an insulation property; at least one detection unit that is provided on at least one of the first insulation portion and the second insulation portion; and a first wiring which is provided on at least one of the first insulation portion and the second insulation portion, and in which one end is electrically connected to one terminal of the detection unit and the other end is electrically connected to the substrate having the electrical conductivity.

Abstract: A heater according to embodiments includes: a base portion which contains metal, extends in a first direction, and has a first surface and a second surface facing the first surface; an insulating layer which is provided on the first surface side of the base portion; a heating element which is provided on the insulating layer and extends in the first direction; and a protection portion which covers the heating element. A peripheral edge of the base portion in a second direction intersecting the first direction extends in a third direction intersecting the first direction and the second direction.

Abstract: A heater includes: a substrate including metal and having a shape extending in one direction; a first insulating part provided on a first surface of the substrate; a first heating element provided on the first insulating part and extending along a longitudinal direction of the substrate; a first protection part provided on the first insulating part and covering the first heating element; a second insulating part provided on a second surface of the substrate facing the first surface; a second heating element provided on the second insulating part and extending along the longitudinal direction of the substrate; and a second protection part provided on the second insulating part and covering the second heating element. A length of the second heating element is different from a length of the first heating element in the longitudinal direction of the substrate.

Abstract: A heater includes: a substrate; a heating element, provided on a first surface of the substrate and extending in a longitudinal direction of the substrate; a protection part, provided on the first surface, extending in the longitudinal direction of the substrate, and covering the heating element; and at least one relaxation part, provided on a second surface of the substrate facing the first surface. A coefficient of thermal expansion of the protection part and a coefficient of thermal expansion of the at least one relaxation part are different from a coefficient of thermal expansion of the substrate. A material of the at least one relaxation part is the same as a material of the protection part, or a main component of the material of the at least one relaxation part is the same as a main component of the material of the protection part.