Types of clock

Clocks

Clocks are used to measure time intervals. So many clocks are being used from the ancient time. Scientists have modified the mechanism of the clocks everytime to obtain accuracy.

A. Types of clock based on display

There are two types of clocks based on display. They are:

1. Analog clocks

2. Digital clocks

1. Analog clocks

Analog clocks look like a classic 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’. It makes one rotation in one minute and 60 rotations in one hour.

Analog clocks can be driven either mechanically or electronically.

Activity 4

Make a model of an analog clock using card board.

2. Digital clocks

A digital clock displays the time directly. It shows the time in numerals or other symbols. It may have 12 hours or 24 hours display. Recent clocks are showing date, day, month, year, temperature etc. Digital clocks are often called as electronic clocks.

Activity 5

Make a model of a digital clock using match sticks on a card board, with date and time.

B. Types of clock based on working mechanism

There are different types of clocks based on working mechanism.They are:

1. Quartz clock

 2. Atomic clock

1. 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. So, quartz clock is more accurate than mechanical clock. These clocks have an accuracy of one second in every 10⁹ seconds.

2. Atomic clock

These clocks make use of periodic vibrations occurring within the atom. These clocks have an accuracy of one second in every 10¹³ seconds. Atomic clocks are used in Global Positioning System (GPS), Global Navigation Satellite System (GLONASS) and International Time Distribution Services.

Activity 6

You may have heard about the ‘Sun Dial’. Construct a sundial of your own and read out the values from morning to evening. Compare your values with modern clocks.

Greenwich Mean Time (GMT)

 is the mean solar time at the Royal Observatory, located at Greenwich in London. It is measured at the longitude of zero degree.The Earth is divided into 24 zones, each of a width of 15 degree longitude. These regions are called as ‘Time Zones’. Time difference between two adjacent time zones is 1 hour.

Indian Standard Time (IST)

The location of Mirzapur in Uttar Pradesh is taken as the reference longitude of the Indian Standard Time. It is located at 82. 5 degree longitude. IST = GMT + 5:30 hours