8th Science
Term 2 Unit 1
Heat Detail Answers
1. With the help of a neat diagram explain the working of a calorimeter.
- A calorimeter is a device used to measure the amount
- of heat gained or lost by a substance.
- It consists of a vessel made up of metals like copper or aluminium which are good conductors of heat and electricity
- The metallic vessel is kept in an insulating jacket to
- prevent heat loss to the environment,
- There are two holes in it. Through one hole a thermometer is inserted to measure the temperature of the contents.
- A stirrer is inserted through another hole for stirring the content in the vessel.
- The vessel is filled with liquid which is heated by passing current through the hating element.
- Using this device we can measure the heat capacity of the liquid in the container.
2. Write a note on thermostat.
- A thermostat is a device which maintains the temperature of a place or constant.
- The word thermostat is derived from two Greek words, 'thermo' meaning heat and "static' meaning staying the same.
- Thermostats are used any device or system that gets heated or cools down - to circuit on or off when a particular pre-set temperature. It turns an appliance or a temperature is reached.
- Devices which use thermostat include building heater, central heater in a room, air
- conditioner, water heater, as well as kitchen equipments including oven and refrigerators. the controller of a thermal
- Sometimes, a thermostat functions both as the sensor and system.
3. Explain the working of thermos flask.
- A thermos flask has double walls, which are evacuated.
- It is silvered on the inside.
- The vacuum between the two walls prevents heat being transferred from the inside to
- the outside by conduction and convection.
- With very little air between the walls, there is almost no transfer of heat from the inner wall to the outer wall or vice versa.
- Conduction can only occur at the points where the two walls meet, at the top of the bottle and through an insulated support at the bottom.
- The silvered walls reflect radiated heat back to the liquid in the bottle.
8th Science Term 2 Unit 1 Click Here
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