What is the plural of maestro?

This dictionary shows it as MAESTROS.

http://dictionary.reference.com/browse/maestro

how do objects with opposite charges affect each other.

The plural form of "maestro" is "maestros." To understand the plural form of certain words, it's helpful to know the rules of English grammar. In this case, "maestro" is a loanword from Italian. When transforming loanwords into English plurals, we usually add an "s" or "es" at the end. In the case of "maestro," we simply add an "s" to form the plural "maestros." This rule applies to a vast majority of English nouns, with some exceptions where the plural form is irregular.