An Introduction to Electric Current

When charge dqpasses a point in space in time dt,the current at that point is expressed as:

The SI unit for curent is the Ampere (A): 1 A = 1 C/s>

The direction of the current is the direction that the positive charge is moving, oppsite to the direction the negative charge is moving.

In situations where a conductor is present, such as a piece of metal or a thin copper wire, even without any battery or complete circuit present, electrons are moving very rapidly in random motion. These conduction electrons are moving at speeds of 10^6 m/s in all directions. Even if the net charge is zero, these electrons are still present and moving. The net movement of these electrons is zero.

When a potential difference is introduced to a circuit by a battery, these electrons do have a net movement of charge known as electric current.

Current is the net transport of charge through a point p in time t. In a water hose, there is no current because every electron present in a water molecule is matched by a proton present in the molecule.

Current is a scaler quantity because both charge and time are scalers. We represent it with an arrow to show movement even though it is not a vector.

Remember, charge is conserved so the input current must always match the output current.