Maharashtra Board Class 7 Science Solution Chapter 9 – Heat
Balbharati Maharashtra Board Class 7 Science Solution Chapter 9: Heat. Marathi or English Medium Students of Class 7 get here Heat full Exercise Solution.
Std |
Maharashtra Class 7 |
Subject |
General Science Solution |
Chapter |
Heat |
(1) (a) Maximum heat is absorbed by a black colored object.
(b) Radiation of heat does not require a medium.
(c) Conduction of heat takes place through a good conductor substance.
(d) The shining surface in a thermos flask decreases the outgoing heat by reflection.
(e) Cooking utensils are made from metals due to their property of conduction.
(f) The earth receives heat from the sun by radiation.
(2) Steel spoon, soil, wax, water iron griddle will absorb heat.
(3) (a) Putting a cold compress on the forehead of a fever patient, the heat flows from the compress to the body of the patient. The cold object becomes warm and the hot body of the patient becomes cooler.
(b) Rajasthan is a very hot city. So become a hot city, the houses of Rajasthan painted white so that the white colour reflected the heat came from sun, and keeps the houses cool.
(c) There are three modes of heat transfer
(i) Conduction.
(ii) Convection.
(iii) Radiation.
(d) The wind blows from the sea towards the land during day time in sea breeze.
And the wind blows from the land towards the sea during night in land breeze.
(e) Black colour absorb heat from the sun. The outer coat of penguins absorb heat so that the inner body of penguins become warmer than outer region.
(4) (a) Normal glass is a poor conductor of heat when, boiling water is poured into a normal glass the heat expands and the glass crack.
(b) In summer the wire of telephone becomes warm and expand in length, so they sag.
And in winter the temperature is low, the wire cooled down and the wire condense in length, so they become straight.
(d) We know, the thermal conductivity of iron pole is high than wood.
So, An iron Piller feels colder than a wooden pole in winter.