Give reasons.
(a) What is an excellent coolant.
(b) Mercury is used in a thermometer.
(c) A bimetallic strip is used in electrical gadgets.
(d) An iron tyre is heated before fitting it on a wheel.
Give reasons.
(a) What is an excellent coolant.
(b) Mercury is used in a thermometer.
(c) A bimetallic strip is used in electrical gadgets.
(d) An iron tyre is heated before fitting it on a wheel.
(a) Specific heat of water is maximum that is 1 Cal/kg0C. It means that large amount of heat is required to raise the temperature of water by a small value. So water can absorb a large amount of heat. Due to this reason, water is an excellent coolant.
(b) Mercury is used in thermometers because:
1. It does not stick to the glass tube.
2. It expands regularly and uniformly on providing heat to it.
3. It has a lower freezing point and higher boiling point.
4. It is a shining metal and when it expands, the expansion can be easily seen.
(c)The bimetallic strip bends on heating. The amount of bend depends on the temperature and its material. Hence, a bimetallic strip can be used to switch-on or switch-off the electric current in heating or cooling devices. Due to this reason, a bimetallic strip is used in electrical gadgets.
(d) As we know that metal expands on heating and contracts on cooling, On heating, the iron tyre expands, making it easy to fit on a wooden wheel. On cooling, the iron tyre contracts and gets tightly fitted on to the wooden wheel. Due to this reason, an iron tyre is heated before fitting it on a wooden wheel.
(a) Specific heat of water is maximum that is 1 Cal/kg0C. It means that large amount of heat is required to raise the temperature of water by a small value. So water can absorb a large amount of heat. Due to this reason, water is an excellent coolant.
(b) Mercury is used in thermometers because:
1. It does not stick to the glass tube.
2. It expands regularly and uniformly on providing heat to it.
3. It has a lower freezing point and higher boiling point.
4. It is a shining metal and when it expands, the expansion can be easily seen.
(c)The bimetallic strip bends on heating. The amount of bend depends on the temperature and its material. Hence, a bimetallic strip can be used to switch-on or switch-off the electric current in heating or cooling devices. Due to this reason, a bimetallic strip is used in electrical gadgets.
(d) As we know that metal expands on heating and contracts on cooling, On heating, the iron tyre expands, making it easy to fit on a wooden wheel. On cooling, the iron tyre contracts and gets tightly fitted on to the wooden wheel. Due to this reason, an iron tyre is heated before fitting it on a wooden wheel.
