Essential Electrical Concepts, Circuits, and Measurements

Fundamental Electrical Concepts

Voltage (V)

Also known as potential difference between two points in a circuit, voltage indicates the difference in electrical energy between those two points. It is measured in volts (V).

Resistance (R)

Resistance of a material indicates its opposition to the flow of electric current. It is measured in ohms (Ω).

Current Intensity (I)

Current intensity expresses the amount of electric charge flowing per second through a circuit section. It is measured in amperes (A).

Ohm's Law

Ohm's Law describes the relationship between voltage, current, and resistance in an electrical circuit. It is expressed as:

• I = V / R (Current = Voltage / Resistance)

Electrical Energy (E)

The electrical energy (E) consumed by a receiver connected to a circuit is used to produce various effects, such as heat, movement, or light. It is calculated as the product of voltage, current, and time:

• E = V * I * T

Electrical energy is measured in joules (J).

Electrical Power (P)

Electrical power expresses the rate at which energy is consumed by a receiver (energy per second). It is measured in watts (W).

AC Power (Alternating Current)

• P = 1/2 * V * I

DC Power (Direct Current)

• P = E / T = V * I = R * I²

Types of Electric Current

Direct Current (DC)

In Direct Current (DC), electrons flow consistently from the negative pole to the positive pole. The voltage and current intensity remain constant. DC often involves very small values, frequently expressed in milliamperes (mA).

Alternating Current (AC)

Alternating Current (AC) is produced by alternators in power plants. Its frequency depends on the number of times per second the alternator rotates. AC allows for efficient transmission of electrical power over long distances, and higher currents typically require thicker wires.

Common Electrical Measurement Instruments

Ammeter

An ammeter is used to measure the current flow at any point in an electrical circuit.

Voltmeter

A voltmeter is used to measure the voltage (potential difference) between two points in any circuit.

Ohmmeter

An ohmmeter measures the resistance value in ohms (Ω).

Wattmeter

A wattmeter measures the electrical power consumed by an apparatus or machine.

Multimeter

A multimeter is a versatile instrument capable of measuring different electrical quantities such as current, voltage, and resistance. It is the most widely used instrument for electrical measurements.

Circuit Configurations

Series Circuits

In a series circuit, components are connected one after another, forming a single path for current. Key characteristics include:

• Current: The same current flows through each element.
• Voltage: The total voltage is shared among the elements (V_total = V₁ + V₂ + ...).
• Resistance: The total resistance equals the sum of all individual resistances (R_total = R₁ + R₂ + ...).

Parallel Circuits

In a parallel circuit, components are connected across the same two points, meaning they share the same voltage. Key characteristics include:

• Voltage: The voltage across each element is the same.
• Current: The total current is the sum of the currents through each branch (I_total = I₁ + I₂ + ...). The current through each branch is inversely proportional to its resistance (higher resistance, lower current).
• Resistance: The reciprocal of the total resistance is the sum of the reciprocals of individual resistances (1/R_total = 1/R₁ + 1/R₂ + ...).