Mouth to lung convertible electronic cigarettes and methods of using the same

A method of using a mouth to lung convertible electronic cigarette, comprising:

• filling, by a user, E-liquid into an E-liquid storage tank;
• installing, by the user, an electrical power source into a cartridge bottom portion;
• placing, by the user, a switch slider of a vapor control sliding switch to one of a first position and a second position, wherein the first position corresponds to a mouth smoking position where a small E-liquid vapor volume is generated by a first set of heating element, and the second position corresponds to a lung smoking position where a large E-liquid vapor volume is generated by a second set of heating element;
• opening, a first air intake opening, and providing, by the electrical power source, electrical power to the first set of heating element to generate the small E-liquid vapor volume by the first set of heating element, when the switch slider is placed in the first position, and
• opening, a second air intake opening and providing, by the electrical power source, electrical power to the second set of heating element to generate the large E-liquid vapor volume by the second set of heating element, when the switch slider is placed in the second position.