Electric Current And Current Density
Concepts and Equations for Electric Current and Current Density
Electric Current Concepts:

Electric current (I): The rate at which electric charge flows through a conductor.

Conventional current flow: Assumes positive charges move from higher to lower potential.

Electron flow: Electrons actually flow from lower to higher potential.

SI unit of electric current: Ampere (A)  Represents the flow of one coulomb of charge per second.

Relationship between current, charge, and time: I = Q/t, where Q is the charge and t is the time interval.
Current Density Concepts:

Current density (J): The amount of current flowing per unit area of a conductor’s crosssection.

SI unit of current density: Amperes per square meter (A/m²)

Relationship between current density, current, and crosssectional area: J = I/A, where A is the crosssectional area of the conductor.

Current density and drift velocity: J = nqv, where n is the charge carrier density, q is the charge of each carrier, and v is the drift velocity of the carriers.

Ohm’s law in vector form: J = σE, where σ is the conductivity of the material and E is the electric field strength.
Factors Affecting Current Density:

Conductivity (σ): High σ means lower resistance and higher current density.

Electric field strength (E): Stronger E results in higher current density.

Crosssectional area (A): Larger A decreases current density.

Drift velocity (v): Higher v means greater current density.

Temperature: Increased temperature usually reduces conductivity, lowering current density.
Applications of Current Density:

Analysis of current distribution in conductors, e.g., in circuit boards.

Design of electrical circuits and components to optimize performance.

Electroplating: Controlling the thickness and quality of deposited materials.

Semiconductor devices: Understanding current flow and optimizing device efficiency.