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Text. Calorimeters

In simple heat experiments, it is usual to transfer heat to some water contained in a small highly polished copper can, called a calorimeter, and to measure the rise in temperature of water with a thermometer. There is always the dif­ficulty in experiments of this kind that, if we are not careful, some heat will escape before we have had time to measure it. Radiation losses from the calorimeter are reduced to a minimum by being highly polished.1 Secondly, it is always suspended inside a larger can or jacket to protect it from draughts and to prevent the setting up of cold air convection currents2 along its sides. The method of suspending the calorimeter varies. It may be supported by hooks on thin strings or else stood on a poor conductor such as a flat cork. In either case the heat lost by conduction will be very small. Finally, it is desirable to have a cover over the calorimeter to prevent losses both of heat and liquid by evaporation. A calorimeter itself is made of copper, which is a

Fig. 3. Calorimeter set up for

heat measurement.

very good conductor. This ensures that the calorimeter and its contents will attain a uniform steady temperature with the least possible delay3 after a hot body has been placed in it.

Notes

1 by being highly polished — зд. путем хорошей полировки (калориметра)

2 to prevent the setting up of cold air convection cur­rents — помешать возникновению циркуляции холодного воздуха

3 with the least possible delay — без промедления, сразу же

Listen and read words and word combinations to be re­membered:

prevent [pri'vent] препятствовать support [sə'po:t]поддерживать

evaporation [i,vapa'rei∫n] выпари- reduce [ri'dju:s] уменьшать

вание, испарение ensure [in'∫ua] обеспечивать

suspend [sas'pend] подвешивать attain [a'tein] приобретать

cork [ko:k] пробка uniform ['ju:nifo:m] одно-

hook [huk] крючок родный

require [ri'kwaiə] требовать desire [di'zaiə] желать ­

radiation losses потери теплоизлучения

to protect from draughts защитить от сквозняков

poor conductor плохой проводник, изолятор

in either case в любом случае

both of heat and liquid как теплота, так и жидкость through 1 degree на 1 градус

to be made of быть изготовленным из

Give Russian equivalents to the following words without using a dictionary:

calorimeter [,ka la'rimita] method ['meθəd]

experiment [iks'periment] conductor [kən'dAktə]

transfer [ træns’fe: ] finally ['fainəli]

contain [kan'tein] cover ['kAvə]

convection [kən'vek∫n] calorie ['kæləri]

energy [enedji]

63

Models