Electric current is one of the most basic units within electrical and electronic science. Electric current is central to almost every element within electrical and electronic circuits, systems and design. Whether it is an electrical heater, a large electrical grid system, a mobile phone, computer, remote sensor node or whatever, the concept of electrical current is central to its operation.
What is Electric Current?
An electric current is a flow of electric charge in a circuit. More specifically, the electric current is the rate of charge flow past a given point in an electric circuit.
The magnitude of the electric current is measured in coulombs per second, the common unit for this being the Ampere or amp which is designated by the letter ‘A’.
Electric current actually consists of the motion of the electrons. The protons are tightly packed inside the nucleus of an atom whereas electrons are at the outer shells in the orbits around the nucleus. Since electrons are loosely held by the nucleus, they are able to travel freely within the limits of the body. This makes an electric current.
Unit of Electric Current:
How do we measure electric current?
The SI Unit is the Ampere, which is equivalent to a flow of one coulomb per second i.e. 6 x 10¹⁸ charges, i.e. electrons. If there are electrons flowing through our frame in one second then the electrical current flowing through it is ‘One Ampere.’ The current flowing through a typical lightening maybe tens or thousands of amperes and on the other end of the electromagnetic spectrum we have nerve impulses which are in the order of micro amperes.
Visualizing Electric Current:
Imagine an iron beam with a rectangular cross section. Consider one single frame in this beam. Let’s visualize the flow of electrons inside the beam. Let’s consider the electron flow from the right to the left as Qnegative and flow from left to the right as Qpositive. The total resultant electrical current through the frame in the time interval (t) is Qnet = Qpositive – Qnegative. Electric current is nothing net charge through the frame divided by the time interval.
I = Qnet/ t.
Under normal conditions, the electrons are flowing haphazardly inside the body. So the total motions of the electrons through the frame cancel out since there are the same amount going in both directions. If the electric current comes out to be negative then it means that the current is flowing the opposite direction.