Question         Where do we see heat transfer around us?





Learning objective -i                               Heat transfer

  • Every time something heats or something cools down, it is due to heat transfer

  • Whenever the temperature of any object increases or decreases, it is due to heat transfer

  • When the temperature of an object increases (it becomes hotter), it means it is getting  heat from somewhere

  • When the temperature of an object decreases (it becomes colder), it means it is giving  heat to something

learning objective-ii              basic rule of heat transfer

  • Heat always flows from high temperature(hotter things) to low temperature(cooler things) 














Question                                    HEAT TRANSFER IN ACTION

What is happening here?

 





                                                               








Cold ice is transferring its coldness to the hand  - Wrong X
Cold ice is transferring its coldness to the drink - Wrong X

QUESTION                                                  Why do we feel hot or cold?

Heat transfer from hand to ice
Heat transfer from cup to hands



question                  open windows


In winters, people often say- "Don't open the window, you will let the cold in".   Do you agree with this statement? If not, why?
Cold in  X                                                                                                               Heat out 


learning objective-ii              basic rule of heat transfer


          Heat always flows from high temperature(hotter ) to low temperature(cooler) 


          Question                                               Hot or cold?

COLD
HOT 


          Question                                               Hot or cold ?


HOT
COLD

          Question                                               Hot or cold?

HEAT FLOW



HOT /COLD
HOT
COLD


Learning objective iii                                          hot & cold are relative terms                                                           


  • Whether something is hot or cold depends on what you are comparing it with

  • A body at 60 degrees celcius will be hot to a  body at 25 degrees celcius. But the same body will be cold compared to a body at 100 degrees celcius

Experiment                                                DO AT HOME

37 degrees celcius
NORMAL
20 degrees celcius
60 degrees celcius
COLD 

WARM  

          Question                                               Hot or cold?

HEAT FLOW

COLD
HOT 


Experiment                                                DO AT HOME

  The SAME WATER feels cold to one hand feels warm to the other hand. Why?

  HEAT flows from object at higher temperature to object at lower temperature


37 degrees celcius
NORMAL
20 degrees celcius
60 degrees celcius
COLD 

WARM  

Let's revise

  • Whenever the temperature of any object  increases  or  decreases , it is due to heat transfer 
  • Heat always flows from high temperature (hotter things) to low temperature (cooler things) 
  • Hot and cold are relative terms - w hether something is hot or cold depends on what you are comparing it with
Made with Slides.com