The metal wire in an incandescent lightbulb glows when the light is switched on and stops flowing when it is switched off. this simple process is which kind of change?

physical change

Explanation:

A physical change is defined as a change in which there is alteration in shape, size etc. No new substance gets formed in these changes

Example: Melting of ice

A chemical change is defined as a change in which a change in chemical composition takes place. A new substance is formed in these changes.

Example: Corrosion of iron called as rusting.  

Thus when the metal wire in an incandescent light bulb glows when the light is switched on and stops flowing when it is switched off is just a physical change as there is no change in chemical composition.