प्रत्यावर्ती-धारा (a.c.) जनित्र तथा दिष्ट-धारा (d.c.) जनित्र में मूलभूत अंतर क्या है? Pratyavarte Dhaara Janitr Tatha Disht Dhaara Janitr Mein Moolbhoot Antar Kya Hai? Or, What is the Basic Difference Between Alternating Current Generator and Direct Current Generator?