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 cross-section.

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

• Relationship between current density, current, and cross-sectional area: J = I/A, where A is the cross-sectional 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.

• Cross-sectional 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.