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?)

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.

Active:

The boy carried my bag.

Passive:

My bag was carried by the boy.

In the sentence "The boy is made to carry my bag," the verb "carry" is preceded by the word "to". This happens because the verb "made" is used in the passive voice construction in this sentence.

The structure "be + past participle verb" is used to form the passive voice in English. In this case, "is" is the present tense of the verb "to be" and "made" is the past participle of the verb "make".

When using the verb "make" in the passive voice, the structure looks like "be + made + to + infinitive verb". The "to" is added before the infinitive verb ("carry" in this case) because it acts as a marker for the infinitive form of the verb. It indicates that the action of carrying the bag is what the boy is being made or compelled to do.

So, in summary, the addition of "to" before the verb "carry" in sentence #2 is a grammatical requirement when using the verb "make" in the passive voice.