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Challenge: Problem 4

Here is a diagram of an apparatus for measuring the latent heat of vaporization of a liquid S at various temperatures. The tube T leads to a vessel that is kept slightly cooler than the main enclosure. H l and H S are two heating coils. l is the same liquid which is used to control the temperature inside the main enclosure. Taken together, the valve V (which opens to a pump), the heating coil H l , and the liquid l, form a control system. Select those items on the Array which indicate what is prevented from happening by this control system. Then also indicate how this is done.

1
latent heat of steam		 2
flow of mass		 3
constant temperature distribution		 4
mass		 5
unwanted condensation of vapour
6
transfer of heat from electrical element		 7
temperature gradient		 8
radiation losses		 9
transfer of heat by vapour		 10
temperature rise
11
high thermal conductivity		 12
specific heat of substance		 13
condensation of saturated vapour		 14
rate of temperature drop		 15
large surface area
16
insulation against conduction or convection		 17
pressure		 18
cooling inside the enclosure		 19
unwanted conduction of heat 		20
thermal expansion