Abstract: An incandescent light bulb is provided with a plurality of filaments, the first of which is mounted between a first and a second current supply member to emit light upon passage of current therethrough. The remainder of the filaments comprise reserve filaments and are mounted between the first and the second current supply members with electrical connection being established only between the first current supply member and the reserve filaments. Biasing means are provided for urging the second current supply member in the direction of a longitudinal axis defined by the filaments, a biasing force generated by the biasing means being counteracted by the first filament and in later stages of the life of the light bulb by one of the reserve filaments. As a filament burns out and partially disintegrates the biasing force creates electrical contact between a reserve filament and the second current supply member and thereby renders operative a successive reserve filament.