Abstract: A discharge lamp comprises an arc tube 6 made of a translucent ceramic dosed with a metallic halide. The discharge is conducted between electrodes 20 disposed in the arc tube 6. The arc tube 6 comprises a main tube body 11 having a large diameter portion 11A and a small diameter portion 11C, and a narrow tube 12 airtightly fixed to the small diameter portion 11C while penetrating the small diameter portion 11C. In the discharge lamp, supposing that L (mm) is the length of a protrusion from the main tube body of the narrow tube portion 12 and P (W) is the rated power of the discharge lamp, L and P satisfy the relationship (P+268.75)/31.25≦L≦(P+456.25)/31.25 and 200≦P≦450.

Abstract: A switching apparatus wherein the life and the reliability of an electric contact are improved by fundamentally suppressing formation of black powder and activation of the surface of the contact by a chemical reaction. Microcapsules in which organic acid or organic acid precursor from which organic acid is produced as time passes is enclosed are placed into the internal space of an enclosed case so that organic compounds produced on and in the proximity of contact surfaces is oxidized with organic acid which escapes from the microcapsules and vaporized in the enclosed case without forming a film on the surfaces of the contacts to suppress activation of the surfaces of the contacts.