1. Thermal expansion of solids
-Most solids expand when they are heated. The expansion is so little that it cannot be noticed normally. Heating a solid causes increased vibration of the molecules, thus the solid expand. Heating a solid makes its molecules vibrate more vigorously. As the vibration become larger, the molecules are pushed further apart and solid expands slightly in all directions.
2. Thermal expansion of liquids
-Almost all the liquids expands when heated. Like solids, most liquids expand when they are heated. But there are exceptions.
-When liquid expand, it is the increase in volume which has to be considered. Since liquids doesn't have a fixed shape we cannot consider its expansion by length. In general liquids expand more than solids. Different liquids expand by different amounts for the same rise in temperature. This property of the liquids is used in construction of various type of thermometers.
-Whenever liquid is stored in a closed container, an air space must be left for expansion to take place. Car radiator systems have space in them for the coolant to expand, and bottles containing liquids are never completely full when you buy them.
3. Thermal expansion of gases
-Gases expand more than solids and liquids when heated. Gases contain independant particles in random motion. They move faster and faster when the temperature rises. This expands the gases the most. Thermal expansion and contraction in a gas cause its density to change. An increase in the volume of a fixed mass of gas reduces its density. A hot air balloon will rise because the air inside it is heated by a flame and expands. The air become less dense than the surrounding cooler air and the balloon rises. It will fall when the air inside it is cooled.
4. Effects of expansion and contraction
-On expansion, the volume of a substance increases. However, the mass of the substance remain the same. Therefore, the increase in volume will decrease the density. On expansion, density of the heated substance decrease. On contraction, the volume of the substance decreases so the density increases. So on cooling the substance increases the density.
-Substances expand when heated, and very large forces may be setup if there is an obstruction to the free movement of the expanding or contracting bodies. Even through the expansion of solids are not visible, it can produce enough force to crack concrete or buckle steel. And it all happen because vibrating molecules need room to move. When water changes into ice, its volume is increased by 9% which is why water pipes burst if they freezes up.
-Solids don't expand much when heated, but the force produced by the expansion can be very high. Concrete and steel beams used in construction work can cause considerable damage if they do not have space to expand when the temperature rises.
5. Useful applications of thermal expansion
-Rivets are steel bolts used to fasten steel plates firmly together.
-A bimetallic strip is made of two strips of different metals joined together. When heated, one metal(Usually brass) expands more than the other(Usually iron) Consequently, the strip bends and a curve strip is obtained. When cooled, the strip bends the other way.
-Bimetal thermostat is a device which used bimetallic strip to keeps temperature constant in electrical appliances.
-Fire alarms make use of the bimetallic strip to close an circuit and trigger an alarm.
-Flashing indicators make use of the bimetallic strip to close and open an circuit to make a light flash according to the opening and closing of the contacts.
6. Thermometers
-Temperature is a measure of the hotness or coldness of a object. Thermometers are instruments used for measuring temperature. Any physical property of a material that changes with temperature can be used to measure temperature. There are different kinds of thermometer used for various purposes.
-The different thermometers are: liquid-in glass thermometer(Mercury and Alcohol type), clinical thermometer, bimetallic thermometer, thermocouple thermometer and resistance thermometer.
-Most solids expand when they are heated. The expansion is so little that it cannot be noticed normally. Heating a solid causes increased vibration of the molecules, thus the solid expand. Heating a solid makes its molecules vibrate more vigorously. As the vibration become larger, the molecules are pushed further apart and solid expands slightly in all directions.
2. Thermal expansion of liquids
-Almost all the liquids expands when heated. Like solids, most liquids expand when they are heated. But there are exceptions.
-When liquid expand, it is the increase in volume which has to be considered. Since liquids doesn't have a fixed shape we cannot consider its expansion by length. In general liquids expand more than solids. Different liquids expand by different amounts for the same rise in temperature. This property of the liquids is used in construction of various type of thermometers.
-Whenever liquid is stored in a closed container, an air space must be left for expansion to take place. Car radiator systems have space in them for the coolant to expand, and bottles containing liquids are never completely full when you buy them.
3. Thermal expansion of gases
-Gases expand more than solids and liquids when heated. Gases contain independant particles in random motion. They move faster and faster when the temperature rises. This expands the gases the most. Thermal expansion and contraction in a gas cause its density to change. An increase in the volume of a fixed mass of gas reduces its density. A hot air balloon will rise because the air inside it is heated by a flame and expands. The air become less dense than the surrounding cooler air and the balloon rises. It will fall when the air inside it is cooled.
4. Effects of expansion and contraction
-On expansion, the volume of a substance increases. However, the mass of the substance remain the same. Therefore, the increase in volume will decrease the density. On expansion, density of the heated substance decrease. On contraction, the volume of the substance decreases so the density increases. So on cooling the substance increases the density.
-Substances expand when heated, and very large forces may be setup if there is an obstruction to the free movement of the expanding or contracting bodies. Even through the expansion of solids are not visible, it can produce enough force to crack concrete or buckle steel. And it all happen because vibrating molecules need room to move. When water changes into ice, its volume is increased by 9% which is why water pipes burst if they freezes up.
-Solids don't expand much when heated, but the force produced by the expansion can be very high. Concrete and steel beams used in construction work can cause considerable damage if they do not have space to expand when the temperature rises.
5. Useful applications of thermal expansion
-Rivets are steel bolts used to fasten steel plates firmly together.
-A bimetallic strip is made of two strips of different metals joined together. When heated, one metal(Usually brass) expands more than the other(Usually iron) Consequently, the strip bends and a curve strip is obtained. When cooled, the strip bends the other way.
-Bimetal thermostat is a device which used bimetallic strip to keeps temperature constant in electrical appliances.
-Fire alarms make use of the bimetallic strip to close an circuit and trigger an alarm.
-Flashing indicators make use of the bimetallic strip to close and open an circuit to make a light flash according to the opening and closing of the contacts.
6. Thermometers
-Temperature is a measure of the hotness or coldness of a object. Thermometers are instruments used for measuring temperature. Any physical property of a material that changes with temperature can be used to measure temperature. There are different kinds of thermometer used for various purposes.
-The different thermometers are: liquid-in glass thermometer(Mercury and Alcohol type), clinical thermometer, bimetallic thermometer, thermocouple thermometer and resistance thermometer.
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