Question

We elected balu captain in active voice

Answer 1

Hey dear.....

Your answer is.....

Balu Captain was elected by us.

Hope this helps. Thank you.

Answer 2

$\large\underline\bold{Correct\:Question:}$

We elected Balu as captain.
Change to passive voice.

$\large\underline\bold{Answer:}$

As the sentence is already in active, so your actual question must be to convert to passive voice.

Let us begin!

The passive form of the given sentence would be as follows:
Balu was elected captain by us.

Earlier the sentence form was,
Subject + Verb + Object

On changing to passive form,
Object + is/was/were + Verb + Subject