Points to Remember
* The need of standard units for physical quantities was recognised in the 11th General Conference on Weights and Measures in 1960.
* Length, mass, time, temperature, electric current, amount of substance and luminous intensity are called base quantities.
* Temperature is the measure of hotness or coldness of a substance. Its SI unit is kelvin.
* Electric charge is measured in coulumb and electric currect is measured in ampere.
* The SI unit of amount of substance is mole.
* Luminous intensity is measured in candela.
* Quartz clock uses the ‘electronic oscillations’ controlled by a ‘quartz crystal’.
* Atomic clock uses the ‘periodic vibrations occurring within the atom’.
* Accuracy is the closeness of a measured value to the actual value.
* Precision is the closeness of two or more measurements to each other.
* Approximation is the process of finding the solution by means of ‘estimation’.
1. Amount of substance Measure of number of entities (particles) present in a substance.
2. Calibration Process of configuring an instrument in a particular range.
3. Electric current Flow of electric charges (electrons) in a unit time.
4. Electronic Oscillation Oscillations produced by an electronic circuit.
5. Luminous Intensity Amount of light emitted by a light source in a particular direction per unit time.
6. Plane angle Angle made at the point of intersection of two lines or planes.
7. Quartz Crystal Crystal formed by Silicon and Oxygen (SiO2).
8. Solid angle Angle made at the point of intersection of three or more planes.
1. Units and Measurements – John Richards, S. Chand publishing, Ram nagar, New Delhi.
1. h t t p : / / w w w. n p l . c o . u k / r e f e r e n c e / measurement-units/
This activity enables the students to learn about the various types of Time keeping devices
* Open the Browser and type URL link given below (or) Scan the QR Code.
* Click and select the “History of time keeping devices”
* Options will be given. Select any content (Eg) Digital clock
* It gives clear understanding of the “History of time keeping devices”
Web link: https://playablo.com/Blog/5-fun-activities-to-teach-temperature-hot-and-cold-to-preschoolers/https://en.wikipedia. org/wiki/History_of_timekeeping_devices
(or) scan the QR Code
*Pictures are indicative only