Alternating current, as we saw, periodically reverses its direction, whereas direct current (DC) flows always in the same direction. The amount of current can change in a DC circuit, but their general direction remains the same.
Perhaps the best and the simplest example of direct current is a battery. Take a look at one of them in your house. You can spot two terminals – +ve and -ve. If a wire is connected to these two terminals, it will cause a flow of electrons resulting in the production of electricity.
Other than this, direct current is used as power supply for electronic systems and also for charging batteries. DC is thus used for many purposes, though for smaller and less complicated ones, unlike AC power. But direct current can be converted to alternating current through devices like an inverter or a motor-generator set.
Direct current is produced by various sources such as solar cells, dynamos etc. It mainly flows in good conductors such as wire, but can also flow through semiconductors, insulators and even vacuum.
Electric current in DC is measured in ampere and voltage in volts.