Clock

Class 8 Clocks

1. CLASS VIII SCIENCE PART VII CLOCKS

2. CLOCKS What is a Clock? A clock is a mechanical or electrical device for measuring time. It is used to measure time intervals. It indicates hours, minutes and sometimes seconds.

3. Many clocks were used from the ancient time, but these clocks were not accurate. So, scientists modified the clock’s mechanism to obtain accuracy.

4. Types of clocks based on display Analog clock It has three hands to show the time. Hours Hand : It is short and thick. It shows ‘ Hour ’ Minutes Hand : It is long and thin. It shows ‘ Minute ’ Seconds Hand : It is long and very thin. It shows ‘ Second ”

5. 2. Digital clocks A digital clock displays the time directly. It shows the time in numerals or other symbols. It may have a 12 hours or 24 hours display.

6. Types of clock based on working mechanism Quartz Clock These clocks are activated by ‘electronic oscillations’, which are controlled by a ‘quartz crystal’. The frequency of a vibrating crystal is very precise. The quartz clock is more accurate than the mechanical clock.

7. 2. Atomic clock Atomic clocks are the most accurate clocks. These clocks are making use of periodic vibrations occurring within the atom.

8. Uses of atomic clocks. Atomic clocks are used in Global Positioning System (GPS) Global Navigation Satellite System (GLONASS) International Time Distribution Services.

9. ASSIGNMENT Mention the types of clocks based on the display. How many minutes are there in one hour? What type of oscillations are used in quartz clock? Write a short note on different types of clocks.