Question: What is meant by DC?
Answer: Direct current (DC) is the unidirectional flow of an electric charge. This means that it 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 purpose, though for smaller and less complicated ones, unlike AC power. But direct current can be converted to alternating current through devices like an invertor or a motor-generator set.
Direct current is produced by various sources such as solar cells, dynamos etc. It mainly flows on good conductors such as wire, but can also flow through semiconductors, insulators and even vacuum. Electric current on DC is measured in ampere and voltage in volts.
For a direct current (DC) voltage source, the polarity of the terminals does not change, so the resulting current constantly flows in the same direction.
The direction of an electric current is by convention the direction in which a positive charge would move. Thus, the current in the external circuit is directed away from the positive terminal and toward the negative terminal of the battery. Electrons would actually move through the wires in the opposite direction.
Knowing that the actual charge carriers in wires are negatively charged electrons may make this convention seem a bit odd and outdated. Nonetheless, it is the convention that is used worldwide and one that a student of physics can easily become accustomed to.