Read the following first.
1. I wrote this aticle.
2. This article was written by me.
From the two sentences above, I changed the active voice to passive voice.
(The word wrote was changed to was written.)
However, if we finish writing an article, we may also write Written by.
So why do we need to use written in that case? Can we use was written or wrote instead?
Please explain in detail and in English.