WAZIPOINT Engineering Science & Technology: Electric Current and Ohm’s Law

Sunday, January 21, 2024

Electric Current and Ohm’s Law

Electric current and Ohm's law is very much essential parts of knowing as an electrical engineer.  I'll provide brief explanations for each term:

Electron Drift Velocity:
The average velocity of electrons in a conductor in response to an electric field.

Charge Velocity and Velocity of Field Propagation:

Charge velocity refers to the movement of electric charge, typically electrons. The velocity of field propagation is the speed at which changes in the electric field travel through a medium.

The Idea of Electric Potential:

Electric potential, or voltage, is the electric potential energy per unit charge at a point in space. It represents the work done by an external force in bringing a charge from infinity to that point.

Resistance:
The opposition that a material offers to the flow of electric current.

Unit of Resistance:
The unit of resistance is the ohm (Ω).

Law of Resistance:
Ohm's Law states that the current passing through a conductor between two points is directly proportional to the voltage across the two points, given a constant temperature.

Units of Resistivity:
Resistivity is measured in ohm-meter (Ω·m).

Conductance and Conductivity:
Conductance is the reciprocal of resistance. Conductivity is the measure of a material's ability to conduct electric current and is the inverse of resistivity.

Effect of Temperature on Resistance:
Generally, the resistance of conductors increases with an increase in temperature.

Temperature Coefficient of Resistance:
A measure of how much a material's resistance changes per degree Celsius change in temperature.

Ohm’s Law:
States the relationship between voltage, current, and resistance:
V=I×R.

Resistance in Series:
The total resistance in a series circuit is the sum of individual resistances.

Voltage Divider Rule:
A rule used to find the voltage across a specific resistor in a series circuit.

Resistance in Parallel:
The reciprocal of the total resistance in a parallel circuit is equal to the sum of the reciprocals of the individual resistances.

Types of Resistors:
Resistors can be fixed or variable. They come in various forms such as carbon composition, film, wire-wound, etc.

Nonlinear Resistors:
Resistors whose resistance changes with voltage or current, like varistors.

Varistor:
A variable resistor whose resistance decreases with increasing voltage.

Short and Open Circuits:
A short circuit occurs when there is a low-resistance connection between two points, bypassing the normal load. An open circuit occurs when there is a break in the circuit,

‘Shorts’ in a Series Circuit:
A short circuit in a series circuit would interrupt the flow of current.

‘Opens’ in Series Circuit:
An open circuit in a series circuit would also interrupt the flow of current.

‘Open’s in a Parallel Circuit:
An open circuit in a parallel circuit would not affect the other branches.

‘Shorts’ in Parallel Circuits:
A short circuit in a parallel circuit would create a low-resistance path for current.

Division of Current in Parallel Circuits:
The total current entering a parallel circuit is divided among the different branches.

Equivalent Resistance:
The single resistance value can replace a set of resistors in a circuit without changing the overall current or voltage.

Duality Between Series and Parallel Circuits:
There is a mathematical relationship between series and parallel circuits called electrical duality.

Relative Potential:
The electric potential at a point relative to some reference point.

Voltage Divider Circuits:
Circuits where a series of resistors divide the voltage in a predictable manner.
These concepts collectively form the foundation of understanding electrical circuits and their behavior.