Electrical and electronic principles are fundamental to the design, operation, and maintenance of industrial mechatronics systems. Understanding basic electrical quantities and the behaviour of materials as conductors or insulators is essential for troubleshooting, system integration, and safety in Kenyan industrial environments. This chapter covers the essential units used to quantify electrical phenomena and explores the characteristics that distinguish conductive from insulating materials, both critical for mechatronics technicians working with automated machinery and control systems.

2.1 Basic SI units of basic electrical

Electrical quantities are measured using the International System of Units (SI), which provides a universal framework for quantifying voltage, current, resistance, and other parameters. Precise measurement and calculation using these units are crucial for configuring and diagnosing mechatronic devices in various Kenyan industrial settings such as manufacturing plants and automated farms.

2.1.1 Overview of SI Units quantities

Electrical quantities are expressed in specific SI units that define their magnitude and dimension. The fundamental electrical quantities include voltage (potential difference), current, resistance, charge, power, and energy.

• Voltage (V): The electric potential difference between two points, measured in volts (V). It represents the energy per unit charge.
• Current (I): The flow of electric charge through a conductor, measured in amperes (A). One ampere corresponds to one coulomb of charge passing per second.
• Resistance (R): The opposition to current flow in a material, measured in ohms (Ω). Resistance depends on material, length, and cross-sectional area.
• Charge (Q): The quantity of electricity held or transferred, measured in coulombs (C).
• Power (P): The rate at which electrical energy is converted or used, measured in watts (W). Power equals voltage times current.
• Energy (E): The total electrical work done or consumed, measured in joules (J). Energy is power multiplied by time.

Worked Examples

Example 1:
Calculate the power consumed by a motor operating at 240 V with a current of 5 A.
Given: \( V = 240\,V \), \( I = 5\,A \)
Formula: \( P = V \times I \)
Substitution: \( P = 240 \times 5 \)
Calculation: \( P = 1200 \)
Answer: 1200 W

Example 2:
Find the charge transported by a current of 3 A flowing for 10 seconds in an automated packaging machine.
Given: \( I = 3\,A \), \( t = 10\,s \)
Formula: \( Q = I \times t \)
Substitution: \( Q = 3 \times 10 \)
Calculation: \( Q = 30 \)
Answer: 30 C

Example 3:
An actuator has a resistance of 12 Ω and is connected to a 48 V supply. Calculate the current flowing through it.
Given: \( R = 12\,\Omega \), \( V = 48\,V \)
Formula: \( I = \frac{V}{R} \)
Substitution: \( I = \frac{48}{12} \)
Calculation: \( I = 4 \)
Answer: 4 A

Example 4:
Determine the energy consumed by a conveyor motor running at 1200 W for 3 hours in a factory.
Given: \( P = 1200\,W \), \( t = 3\,h = 10800\,s \)
Formula: \( E = P \times t \)
Substitution: \( E = 1200 \times 10800 \)
Calculation: \( E = 12960000 \)
Answer: 1.296 \times 10^{7} \, J

Example 5:
Calculate the voltage across a sensor with resistance 5 Ω when a current of 2 A flows through it.
Given: \( R = 5\,\Omega \), \( I = 2\,A \)
Formula: \( V = I \times R \)
Substitution: \( V = 2 \times 5 \)
Calculation: \( V = 10 \)
Answer: 10 V

Chapter Summary

This chapter introduced the fundamental SI units essential for understanding electrical quantities, including power measured in watts, current in amperes, resistance in ohms, and voltage in volts. It covered the distinction between conductors and insulators by examining the properties of metals and non-metals and their roles in electrical circuits. The chapter further explored key electrical quantities such as charge, force, work, and power, providing their definitions, units, and methods for performing related calculations. A detailed study of Ohm's law was presented, highlighting its significance and practical application in solving electrical problems. Additionally, basic electrical and electronic measurement techniques were discussed, focusing on the correct use of instruments like multimeters and ammeters. The importance of accurate measurement calibration was also emphasized to ensure reliable results. Overall, the chapter equipped learners with the foundational principles and skills necessary for applying basic electrical concepts in practice.