Basic Terminologies of Electric Circuits

BASIC TERMINOLOGIES OF ELECTRIC CIRCUITS

Electric current

Electric current is the rate of flow of electric charges. Electrons are negatively charged particles and their flow in conductors results in electric current.

By definition, current,

If Q is the amount of charge flowing through a conductor in T seconds, then current I is given by the expression,

The unit of charge is Coulomb. 1 Coulomb 6.24 × 1018 electrons. The unit of current is Ampere(A). 1 Ampere = 1 Coulomb/sec.

Electromotive force (e.m.f)

Energy is required for the movement of charge from one point to another. In order to move electrons along a conductor, some amount of work is required. The work required is supplied by an electromotive force (e.m.f) provided by a battery or a similar device.

Potential difference

Potential difference is the difference between the voltages at two ends of a conductor.

A current carrying element is shown in the figure 2. The voltage across the element, Vab is given by,

Where work done (W) is measured in Joules and the charge (Q) in Coulombs.

The positive (+) and negative (-) signs shown in figure 1.2 define the polarity of the voltage Vab. With this definition, Vab represents the voltage at point 'a' relative to point 'b'.

Electric circuit

An electric circuit is a closed connection formed by various electric elements (Resistors, inductor, capacitor, voltage source, current source, etc.)

The fundamental circuit model is shown in the figure 1.3. The circuit is made up of a source Vs which provides a voltage across its terminals and a load resistor RL.