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Book 1A
Heat
 
 
 
Book 1B
Mechanics
 
 
 
Book 1C
Waves
 
 
 

Book 2
Electricity and Magnetism

 
 
 
Atomic Physics
 
 

Difference between conductor and insulator

For a metal rod and a wooden rod of the same length, which one conducts heat faster? Why? (Extension)

One of the differences between metals and non-metals is that metals can conduct heat much faster than non-metals. What makes them different in conducting heat? It is because one has electrons moving freely inside the body and the other has not.

Structure of matter
What is electron? All matters (solids, liquids and gases) are made up of very tiny things called atoms. Each atom has a nucleus with some electrons moving around; some electrons are more loosely held by the nucleus and different materials have different number of electrons at their atoms (Fig a).

 
Fig a    In an atom of a certain material, some electrons moving around a nucleus.
  Fig b    Atoms are closely packed inside a solid metal.

Free electrons
In solids, atoms are packed close together (Fig b). For metals, those loosely held electrons of atoms would no longer be bounded by any atom; they move freely inside the solid metal. These freely moving electrons are called free electrons. For non-metals, most electrons are bounded by the atoms.

What do free electrons do when metals are heated?
When an end of a metal rod is heated, both atoms and free electrons at the hotend gain energy; atoms vibrate vigorously and free electrons move at a highspeed. When these high-energy atoms or free electrons collide with their neighbouring atoms with lower energy, they would lose energy to neighbouringatoms. Since free electrons are present in metals, metal atoms are hit morefrequently than non-metal atoms when heated. Hence, metals can be heated muchfaster than non-metals.

 
   
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