For example, the tense may change between the methods section and the discussion section. The abstract is usually in the past tense due to it showing what has already been studied. Example: “This ...

However, if you are writing about the writer of the text when they are no longer alive, you can use the past tense. For example: 'Dickens was interested in those characters on the edges of society.' ...

However, changing the tense deliberately can have a positive impact on your reader. For example, if you were writing a persuasive speech you may swap from the past tense to the present tense to ...