Understanding Physical Quantities and Measurement Principles

Posted on Feb 27, 2025 in Electromechanical Engineering

Understanding Physical Quantities and Measurement

Define the term ‘physical quantities’.

Physical quantities are all those properties or qualities of matter, energy, and measurable space.

Identify which of the following are physical quantities:

Density, Volume, Length, Temperature, Area, Pressure, Time.

Note: Ira, Patriotism, Beauty, Citizenship, Feeling, and Love are not physical quantities.

What is Measurement?

Measurement is the process of comparing two magnitudes of the same nature, using one as the standard.

Direct vs. Indirect Measurement

What is the difference between a direct measure and an indirect measure? Provide examples of each.

Direct Measurement: In direct measurement, the quantity to be measured is directly compared with the selected unit of measure.

Indirect Measurement: In indirect measurement, the value of a quantity is obtained by measuring other quantities and performing certain operations with this data.

Importance of Measurement in Life Sciences and Health

Measurement is crucial in the natural sciences, providing better information about what is being studied. It is also vital in healthcare, aiding physicians in discovering new diagnostic methods, such as radiation and chemotherapy.

Initial Physical Quantities Measured by Doctors

What physical quantities are initially measured by a doctor when a patient seeks consultation?

Temperature, Mass, Arterial Pressure, Beats Per Minute, Patient Age.

Causes Affecting Measurement

What are the causes that affect a measurement?

Every measurement is subject to error. Common causes include:

• The type of instrument used
• Environmental factors
• Personal factors
• The method used in measuring

Parallax Error

What is parallax error?

Parallax error occurs when an object is measured erroneously because our vision is not perpendicular to the scale of the measuring instrument.

Systematic Error

When does a systematic error occur during measurement?

Systematic errors can be produced by the measuring instrument, a peculiarity of the operator, or the measurement process itself.

Order of Magnitude

What is order of magnitude?

Order of magnitude helps understand the scale of a measurement. If a measure on the natural scale has a value between 1 and 3, it is closer to 10⁰ (1). If it’s from 3.20 to 10, it is closer to 10¹ (10).

Significant Figures

What are significant figures in a measurement?

Significant figures are those digits in a measurement about which we are reasonably certain.

Criteria for Limiting Significant Figures

What criteria are used to limit the number of significant figures in a measurement?

Zeros are generally not considered significant figures unless they are located to the right of a non-zero digit or between non-zero digits.

Uncertainty in Measurement

What is the uncertainty in a measurement?

Uncertainty, or the uncertainty of a measure, is the absolute value of the difference between the measured value (x) and the best estimate of the value (x’).

Analog vs. Digital Measuring Instruments

What is the difference between an analog measuring instrument and a digital one?

A digital measuring instrument is generally more accurate when used correctly.

Unit of Measurement

What is a unit of measurement, and how do you define it?

A unit of measurement is a standard quantity used to express a measurement. Examples include pounds, milligrams, seconds, and minutes. This unit is always accompanied by a numeric value.

Yardstick

What is a yardstick?

A yardstick is the materialization or conceptualization of a unit of measurement. These are established for legal and scientific purposes to standardize measurements and must remain unchanged and accessible.

International System of Units (SI)

What is the International System of Units, and what are its magnitudes and fundamental units?

Conversion Factors

What are conversion factors?

Conversion factors are a system used to convert a given number of units from one system to another.