Conduction



Question                       

What do you expect when you put the spoon in a cup of hot tea?


  

Question

  a.  Temperature of the spoon stays at 25 degrees celsius

  b.  Temperature of the spoon will be more than 25 degrees celsius

   c.   Temperature of the spoon will be less than 25 degrees celsius

The metal spoon is at 25 degrees celsius and  it is put in cup of tea which is at 80 degrees celsius. After 2 minutes, touch the top end of the spoon gently. What do you expect?

question                            


Let's look at the steps involved in heat transfer from tea to hand

Heat transfer from tea to head of spoon 
Heat transfer from head of spoon to handle
Heat transfer from handle to hand

All these are examples of heat transfer by touch or contact

learning Objective-i         HEAT TRANSFER by contact




learning Objective-i                             CONDUCTION


  • Whenever two objects at different temperature come in contact (TOUCH) heat flows from the object at higher temperature to the object at lower temperature

  • The transfer of heat by TOUCH  or contact is called CONDUCTION


Conduction is also responsible for transfer of heat through a solid, from one end to another 

question                            

 

Heat is transferred from tea to head of spoon by conduction
Heat is transferred from head of spoon to handle by conduction
Heat is transferred from handle to hand by conduction

experiment                               HEAT TRANSFER THROUGH A Solid


                                          


Learning objective                                   

  • Conduction is responsible for transferring heat from one part of the object to other parts

  • In solids, generally, heat is transferred by the process of conduction

Question 

Where else have you seen heat transferred from one part of the object to other parts?




experiment                                         

Heat takes different time to travel the same distance through different materials


Learning Objective                                         conductors & Insulators


  • Objects in which heat transfers quickly from one end to other are said to be good conductors of heat 

  • Objects in which heat transfer from one end to other is slow are said to be bad conductors of heat

  • Poor conductors of heat are also called insulators. 

Question                                                     



In this experiment, out of the 5 materials, which was the best conductor of heat? Look at the timings for information

Question

Which of these two materials would you prefer for a cooking pan's handle & why ?

a. Copper           b. Steel           c. Plastic

 

Challenges

The cylindrical rod is made of alternating metal & wooden strips. Paper is wrapped over the rod.  video at 3:43









Why can we see burnt marks for wooden parts but no burnt marks for metallic parts?
Hint :  Burnt marks occur only when the paper reaches a certain temperature
 


ADVANCED Topics              HOW is heat transferred from one end to the other?


ADVANCED TOPICS              HOW IS HEAT TRANSFERRED FROM ONE END TO THE OTHER?


http://www.bbc.co.uk/bitesize/standard/physics/energy_matters/heat_in_the_home/revision/1/
Made with Slides.com