A Direct Current (DC) is a constant values of current which does not change with the time. It flows in one direction only, that is from positive to negative. The current here does not change its direction at all. It is always from positive terminal to negative terminal.
Disadvantage of Direct current:
Generally, the electricity is produced in a power plant which is far away from the main city. To supply the electricity to houses we have to transport it into the city. Electricity is transported through wire.According to Joule's law of heating, If we transport electricity form of Direct Current through wires, a major portion of the electricity is already lost and wasted in form of heat which will cause nothing but loss. This is the major disadvantage of the Direct Current. It is prevented by transporting Alternating Current instead of direct current. Which does not really have heating problem.