When electric current flows through the thin filament of an electric bulb, the filament becomes extremely hot and starts to glow, emitting light. This is an example of the heating effect of electric current. The magnetic effect involves the creation of a magnetic field around a current-carrying wire, and the chemical effect involves chemical changes due to current, neither of which is the primary reason for a bulb's glow. There is no such thing as a 'pressure effect' of electric current.