Basic Electrical Principles: International System of Measurement and Fundamental Concepts, Study notes of Electrical Engineering

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CHAPTER ONE

• International System of Measurement
• Base units and Derived units
• Definitions of units
• Basic Electrical Principles

INTERNATIONAL SYSTEM OF

MEASUREMENT

• Internationally the international system of measurement is known as SI and is based on the measurement of seven physical quantities - From French S ystème I nternational d`unités

INTERNATIONAL SYSTEM OF

MEASUREMENT

Study Table 1.1, 1.2 and 1.

• List Of Symbols And Abbreviations
• Abbreviations For Multiples And Sub- multiples

Multiples and Submultiples

Determine the answers to the following calculations and express your answers in normal , scientific and engineering modes :

1. 45mm x 60mm
2. 10mm 2 x 20cm
3. 20 tons + 500kg
4. 20nF +12pF
5. 100kΩ +10MΩ
6. 45cm 3 ÷ 12cm

FORCE

• A force is anything that causes movement or tends to cause movement.
• When a body is to be accelerated, a force must be applied proportional to the desired rate of change of velocity, i.e. proportional to the acceleration

Force

Weight

• The gravitational force acting on a mass
• The force exerted by the earth’s centre on a body
• All material forces are subject to gravitational forces
• Irrespective of their mass , fall with one and the same value of the acceleration , which is about 9,81 m/s 2

Weight

Newton - Definition

The Newton is the force which , when applied to a body with a mass of one kilogram , gives it an acceleration of one metre per second squared

WORK AND ENERGY

• Energy means the capacity to do work
• An object possesses energy if the object is capable of doing work N Frictional force F F W s m

WORK AND ENERGY

W = F.s W  work done, in J , when an object is moved a distance because of a force acting on it s  distance through which the object moved in m

Potential Energy

• When a weight is lifted a distance above a plane, the weight possesses a capacity of doing work by virtue of its position above the plane

Potential Energy

Is always associated with an object on certain conditions:

• If work is done on the object against forces to change the position of the object
• If this work can be fully recovered by allowing the object to return to its original position

Kinetic Energy