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ICSE-X-Physics

Previous Year Paper year:2017

with Solutions - page 4

#6

#6-a

#6-a-i [3]
How is the transference of heat energy by radiation prevented in a calorimeter?
Ans : The outer and inner vessels of a calorimeter are highly polished to
prevent the transference of heat energy by radiation.

#6-a-ii
You have a choice of three metals A,B and C, of specific heat capacities ``\pu{900 J//Kg °C}``,``\pu{380 J//Kg °C}``,``\pu{460 J//Kg °C}`` respectively, to make a calorimeter. Which material will you select? Justify your answer.
Ans : Metal B with specific heat capacity 380 Jkg.10C.1 should be selected to
make a calorimeter. By selecting this metal, the heat capacity of the
calorimeter will be reduced and the amount of heat energy consumed by
it from its contents to acquire their final temperature will also be
negligible.

#6-b [3]
Calculate the mass of ice needed to cool 150g of water contained in a calorimeter of mass 50 g at ``\pu{32°C}`` such that the final temperature is 5°C.
Specific heat capacity of calorimeter = ``\pu{0.4 J//g °C}``
Specific heat capacity of water = ``\pu{4.2J//g °C}``
Latent heat capacity of ice = ``\pu{330 J//g}``
Ans : Heat enegy imparted by water
$$ = Mass_{water} * Specific Heat Capacit_{water} * (t_1- t_2)$$
=150 *4.2 *(32-5) = 17010 J
If 'm' g is the amount of ice used,
then heat energy taken by ice to melt = m*Latent heat capacity of ice
= 330* m = 330 m
And heat energy taken by the
melted ice to raise its temperature from 0 to 5 C
m * 4.2* (5- 0) = 21m
By law of conservation of energy,
Heat energy imparted by water=heat energy taken by ice and melted ice
17010= 330m+ 21m
17010= 351m
m= 48.46 g
Amount of ice required for this process is 48.46 gm.

#6-c [4]

#6-c-i
Name the radiations which are absorbed by greenhouse gases in the earth’s atmosphere.
Ans : Infrared radiations of long wavelengths are absorbed by greenhouse
gases in the Earth.s atmosphere.

#6-c-ii
A radiation X is focused by a particular device on the bulb of a thermometer and mercury in the thermometer shows a rapid increase. Name the radiation X.
Ans : Radiation X is infrared radiation.

#6-c-iii
Name two factors on which the heat energy liberated a body depend.
Ans : Heat liberated by a body depends on the mass of the body, the specific
heat capacity of that body and the change in temperature experienced by the
body.

#7

#7-a [3]
A lens forms an upright and diminished image of an object when the object is placed at the focal point of the given lens.

#7-a-i
Name the lens.
Ans : The given lens is a concave lens.

#7-a-ii
Draw a ray diagram to show the image formation.
Ans : Ray diagram showing image formation:

#7-b
A ray of light travels from water to air as shown in the diagram given below :

#7-b-i
Copy the diagram and complete the path of the way. Given the critical angle for water is 48°.
Ans : The image formed by the lens is virtual and between the object and the
lens. Hence, the lens used is a concave lens.