1. I made the boy carry my bag.

2. The boy is made to carry my bag.

(#2 is the passive voice of #1. By the way why is 'to' added before "carry" in #2?)

English - Writeacher, Sunday, December 6, 2009 at 8:33pm
One is not exactly the passive of the other. The verb "made" is what you are making passive.

Take a look at these sentences:

John ate a hamburger. <~~active
The hamburger was eaten by John. <~~passive

Try again.

English - Writeacher, Sunday, December 6, 2009 at 8:33pm
Active:

The boy carried my bag.

Passive:

My bag was carried by the boy.
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Thank you. I corrected some.

1. I made the boy carry my bag.
2. The boy was made to carry my bag by me.

(#2 is the passive voice of #1. By the way why is 'to' added before "carry" in #2?)

Both 1 and 2 are grammatically correct. Clearly, 1 is the better sentence.

The word "to" is with "carry" because "to carry" is an infinitive completing the meaning of the verb "made" in the passive.
http://grammar.ccc.commnet.edu/grammar/verbs.htm#infinitives In #1, "to" is simply omitted.

The sentence "The boy was made to carry my bag by me" is indeed the passive voice of the sentence "I made the boy carry my bag."

The reason "to" is added before "carry" in the passive voice sentence is because "to" is used to indicate the purpose or intention of the action. In this case, the intention is for the boy to carry the bag. So, when we change the active voice sentence to passive voice, we include the preposition "to" before the verb "carry" to show the purpose or intention behind the action.