Burnt and burned are two spellings of the same verb. The usage depends on the variant of English.
In British English, both “burned” and “burnt” are used for both the verb and adjective, but burnt-out light bulb is a bit more common.
In American English, “burned” is used as a verb, while “burned” and “burnt” are used interchangeably as adjectives. However, burned-out light bulb is more common in American English.
It’s important to choose one spelling and use it consistently. The QuillBot Grammar Checker can help you with this.