Understanding Direct Current, Ohm's Law, and Electrical Resistance

Understanding Direct Current (DC)

Direct Current (DC) is the electric current flowing consistently in the same direction. The flow of current is determined by three interrelated quantities, the first being the potential difference across the circuit, often referred to as electromotive force or voltage.

Power Generators

A power generator consists of a rotating coil of wire inside a magnet. The magnet is known as the stator, while the rotating loop is called the rotor.

Classification of Generators

Generators are classified based on the currents they produce and their circuit configurations:

• Electromechanical generators
• Electrochemical generators
• Photovoltaic generators
• DC generators
• AC generators

Direction of Electric Current

When an external voltage source (e.g., a battery) is applied to a conducting material, it creates an electric field acting on free electrons. This field causes electrons to move toward the positive terminal, as they are attracted by the positive terminal and repelled by the negative terminal.

Defining Electric Resistance

Electric resistance is the opposition of a material to the flow of electrons. The resistance (R) of a conductor is calculated as R = V / I. In the International System of Units (SI), resistance is measured in ohms, where 1 ohm = 1 volt / 1 ampere.

Ohm's Law Explained

According to Ohm's law, the amount of current flowing through a circuit consisting of pure resistance is directly proportional to the electromotive force applied and inversely proportional to the total circuit resistance. This is expressed by the formula: I = V / R.

Definitions of Ohm and Watt

• Ohm: Defined as the resistance to the passage of electric current through a column of mercury 106.3 cm in length with a 1-millimeter cross-section.
• Watt: The unit of power in the International System of Units, equivalent to 1 joule per second (1 J/s).

Electromotive Force

Electromotive force is the energy provided by any source, medium, or storage device that supplies electric current.

Resistance and Temperature

Temperature is a critical factor when calculating the resistance of a material. The resistance of a metallic conductor increases as temperature rises. This increase depends on the thermal coefficient of resistivity (α), which is defined as the change in resistivity per degree Celsius of variation at 0 °C or 20 °C.