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# 9th Class Chapter 9 Physics Long Questions

Dear students, prepare for physics class 9th chapter 9 long questions. These important long questions are carefully added to get you best preparation for your 9th class physics ch. 9 exams.

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##### Question: 1
What is conduction. Explain it briefly
1-13
Conduction in non-metals: non-metals are bad conductor of heat and the substances through which heat does not conduct are called bad conductors or insulators.Example: wood, cork, cotton, wool, glass, rubber, etc. are bad conductors or insulators.Conclusion: non-metals are insulators thus heat does not conduct through it.
##### Question: 2
What is thermal conductivity ? explain on which factors it depends
2-13
Thermal conductivity: the rate of flow of heat across the opposite faces of a meter cube of a substance maintained at a temperature difference of one kelvin is called the thermal conductivity of that substance.
Unit: Wm-1K-1 is the unit of thermal conductivity.
##### Question: 3
what measures may b taken to save energy?
3-13
In houses good thermal insulator means lower consumption of fuel.
##### Question: 4
Write the uses of conductors and non-conductors
4-13
Uses of conductor: good conductors are used when quick transfer of heat is required through a body. Thus, cooker , cooking plates, boiler , radiators and condensers of refrigerators etc. are made 0f metals such or aluminum as copper . Similarly, metal box are used for making ice creams, etc..
##### Question: 5
Write the uses of conductors and non-conductors.
5-13
Uses of conductor: good conductors are used when quick transfer of heat is required through a body. Thus, cooker , cooking plates, boiler , radiators and condensers of refrigerators etc. are made 0f metals such or aluminum as copper . Similarly, metal box are used for making ice creams, etc..
##### Question: 6
What is convection and convection currents in air? also write its uses
6-13
Convection; transfer of heat by actual movement of molecules from hot place to a cold place is known as convection
##### Question: 7
What is sea an land breezes? also explain the gliding and their uses
7-13
Sea breeze: on a hot day, the temperature of the land increases more quickly than the sea. It is because the specific heat of land is much smaller as compared to water. the air above land gets hot and rise up. Cold air from the sea begins to move towards the land as illustrated. It is called sea breeze.
##### Question: 8
What causes a glider to remain in air? describe
8-13
Gliding: a glider looks like a a small aeroplane without engine. Glider pilots use upward movement of hot air currents due to convection of heat. these rising currents of hot air are called thermals.
Gliders ride over these thermals. The upward movement of air currents in thermals hep them to stay in air for a long period.
##### Question: 9
Define and explain the radiation<div>OR</div><div>How does heat reach us from sun?</div>
9-13
Radiation: radiation is the mode of transfer of heat from one place to another in form of waves called electromagnetic waves. Radiation is that process of heat transfer in which heat energy reaches in the form of waves from one place to other without affecting the medium on its way.
##### Question: 10
What are the factors due to which radiation occurs
10-13
Various factors such as:
• Color and texture of the surface
• Surface temperature
• Surface area
##### Question: 11
Describe use of Leslie cube
11-13
Leslie's cube: a Leslie cube is a meta box having forces of different nature and it used to identify the emission of radiation.
##### Question: 12
What is greenhouse ? also explain<div>t he greenhouse effect in global warming.</div>