Matter Form 1
7.4 Application of expansion and contraction of matter
B6D7E1
1. Knowledge of the principles of expansion and contraction of matter are used widely in our daily lives. Explain with examples of various uses such principles in daily life. Information can be obtained from the internet, magazines, newspapers and other sources. Present your work in class.
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The expansion and contraction of matter can produce very strong forces and is made use of in some applianes in our daily life. The following are some examples of their applications:-
a) Bimetallic strip in the fire alarm
The diagram below shows a bimetallic strip in a fire alarm. The bimetallic strip consists of two types of metals: iron and brass. When the bimetallic strip is heated (during a fire outbreak), this causes the strip to expand and bend to complete the circuit. – This is because brass expands more than iron, causing the iron to curve inwards. Electric currents flow through the circuit causing the bell to ring and water to spray out. When cooled, the strip straightens and the bell will stop ringing.
[pic]
[pic]
b) Thermometer
The property of liquid that expands when heated is used to make thermometer for measuring temperature. Usually mercury or alcohol is used in a thermometer. When the mercury in a thermometer expands, the mercury column moves up the capillary tube. If it contracts, the column falls down. Change in the length of the mercury column is measured by a scale on the stem of the thermometer.
[pic]
[pic]
c) Thermostat in an electric iron
A thermostat is a device used to keep an appliance or a place at a required temperature. Thermostats are used in electric irons, electric kettles, refrigerators, ovens and air- conditioners. An electric iron has a bimetallic thermostat which serves as
B6D7E1
1. Knowledge of the principles of expansion and contraction of matter are used widely in our daily lives. Explain with examples of various uses such principles in daily life. Information can be obtained from the internet, magazines, newspapers and other sources. Present your work in class.
==================================================================
The expansion and contraction of matter can produce very strong forces and is made use of in some applianes in our daily life. The following are some examples of their applications:-
a) Bimetallic strip in the fire alarm
The diagram below shows a bimetallic strip in a fire alarm. The bimetallic strip consists of two types of metals: iron and brass. When the bimetallic strip is heated (during a fire outbreak), this causes the strip to expand and bend to complete the circuit. – This is because brass expands more than iron, causing the iron to curve inwards. Electric currents flow through the circuit causing the bell to ring and water to spray out. When cooled, the strip straightens and the bell will stop ringing.
[pic]
[pic]
b) Thermometer
The property of liquid that expands when heated is used to make thermometer for measuring temperature. Usually mercury or alcohol is used in a thermometer. When the mercury in a thermometer expands, the mercury column moves up the capillary tube. If it contracts, the column falls down. Change in the length of the mercury column is measured by a scale on the stem of the thermometer.
[pic]
[pic]
c) Thermostat in an electric iron
A thermostat is a device used to keep an appliance or a place at a required temperature. Thermostats are used in electric irons, electric kettles, refrigerators, ovens and air- conditioners. An electric iron has a bimetallic thermostat which serves as