It was expected by Alexander that he would conquer the world. Given sentence is in simple past tense and it is in active voice. Rule : Subject + (was/were) + V3 + Other agents
From Voice · English Language Competence Test
The plants have been watered by the gardener.
We should not encourage indiscipline.
Who gave you permission to enter?
A lion may be helped even by a little mouse.
Who gave you ice-cream?
Please help me.
The teacher may punish you.
The boy laughed at the beggar.