<p>The heater (31) has a heating path (25) provided with a curved heating path section (26) e.g. angular and rounded curved heating path section. The heating path comprises a local limited recess (39) in a region of the curved heating path section. The curved heating path section has the recess following a shape of the curved heating path section. The recess is arranged partially parallel over width of the curved heating path section, so that the recess forms partially parallel running heating path strips with partial resistors.</p>