Fundamental and Derived Units in SI

Study Notes

Fundamental and Derived Units

Fundamental units are the base units of a system of measurement. They are independent of other units and defined by physical quantities like length, mass, time, electric current, temperature, amount of substance, and luminous intensity.
Derived units are combinations of fundamental units and describe quantities like area, volume, speed, acceleration, force, and energy.

SI Units (International System of Units)

The SI system is the most widely used system of measurement globally.
It's based on seven fundamental units.
The fundamental units are:
- meter (m) for length
- kilogram (kg) for mass
- second (s) for time
- ampere (A) for electric current
- kelvin (K) for temperature
- mole (mol) for amount of substance
- candela (cd) for luminous intensity
Example derived units include:
- meter per second (m/s) for speed
- meters per second squared (m/s²) for acceleration
- kilograms meter per second squared (kg m/s²) for force (Newton)

Measurement Uncertainty and Error

Measurements are never perfectly precise. There's always some degree of uncertainty associated with any measurement.
Sources of error include:
- limitations of the measuring instrument
- human error in reading the instrument
- environmental factors influencing the measurement process
Accuracy refers to how close a measurement is to the true value.
Precision refers to how close multiple measurements of the same quantity are to each other.

Significant Figures

Significant figures indicate the reliability of a measurement.
Non-zero digits are always significant.
Zeros between non-zero digits are significant.
Trailing zeros in a decimal part of a number are significant.
Leading zeros are not significant.
Rules for rounding significant figures vary depending on the operation being performed.

Dimensional Analysis

Dimensional analysis is a technique used to check the validity of equations by comparing the dimensions of the quantities on both sides.
Units are treated as algebraic quantities that can be cancelled.
Dimensional analysis can also help determine the relationship between variables in a physical law or equation.

Prefixes and Scientific Notation

Prefixes are used to represent very large and very small quantities. They are used to alter the base unit to represent multiples or fractions of them.
Common prefixes include: kilo-, centi-, milli-, micro-, nano-, and mega-.
Scientific notation is used to represent very large or small numbers in a standardized format. This format is often used to reduce the amount of digits and ease calculations.
- Example: 3.0 x 10³ represents 3000.

Different Systems of Units

Besides SI Units, there are older systems of units, such as the CGS (Centimeter-Gram-Second) system.
CGS were commonly used in measuring smaller particles, though SI units have increased in prevalence.

Measuring Instruments

Diverse measuring tools exist for different physical quantities.
Examples include: rulers, graduated cylinders, balances, stopwatches, thermometers, voltmeters, ammeters.
The chosen measuring device should be appropriate for the quantity and accuracy needed. The instrument's limitations and errors need to be considered.

Description

Explore the concepts of fundamental and derived units as defined in the International System of Units (SI). This quiz covers the seven fundamental units, their physical quantities, and examples of derived units used in various measurements. Test your knowledge and understanding of these essential principles of measurement.