Accuracy, Precision Of Instruments And Errors In Measurement
Chapter Name : Units And Measurements |
Sub Topic Code : 101_11_02_06_01 |
Topic Name : Accuracy, Precision Of Instruments And Errors In Measurement |
|
Sub Topic Name : Accuracy, Precision Of Instruments And Errors In Measurement |
|
Introduction
• Measurement and error. • Accuracy and precision in a measurement. • Different types of errors. • Minimizing errors.
Pre-Requisites:
Measurement, SI units
Activity:
• Measure time-period of pendulum for a given length and initial angle of release. • Note that the readings of time period differ slightly from each other. • Next one can use a more precise stopwatch to check for higher precision.
Real Life Question:
Why do we need to average over several readings in an experiment?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| Error | • Always associated with the measurement. • It is the uncertainty allowed in a measurement. |
| Accuracy | • Difference between true value and measured value. |
| Precision | • Limit of measurement, resolution. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Vernier calipers | • Consists of a main scale and a vernier scale. • The smallest length represented by vernier scale is the least count. • If the zero of vernier is not at true zero, there is instrumental error |
| Meter scale | • Least count 1 mm. • May have instrumental error due to worn out ends. |
Real life uses :
• More precise instruments are designed which have minimum error. • Predict future outcomes more accurately, for example path of an asteroid.
Places to visit :
• Your Physics lab may be set-up for measurement of acceleration due to gravity using a simple pendulum. • Meter scale may be found in your study room. • Vernier callipers may also be found from school lab.
Practical examples around us
| Examples | Explainations |
|---|---|
| Shopkeeper’s balance | • You can add or subtract a few grains of rice when purchasing a fixed weight, say 1 kg. |
What you learn in Theory:
• Why do we need to average over several readings in an experiment? • What is the cause of errors? • What are the types of errors? • How can we minimize errors?
What you learn in Practice:
• Get better readings in an experiment.