physics

1. Thermal Conduction Questions
 Q1: During cold weather, iron feels colder when
it is touched compared with wood although both
are at the same temperature. Explain why this
is so.
Answer: Iron is good thermal conductor whereas
wood is a poor thermal conductor. Thermal energy
flows easily from the body to the iron when the
iron is touched. On the other hand, very small
amount of thermal energy flows from the body to
the wood. The loss of energy by the body to the
iron gives the observer a cold feeling.
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2.  Q2:i) Electric conductors usually have
higher thermal conductivity compared to
those that are not conductors of
electricity. Clarify this statement.
 Answer: i) This is because electric
conductors have free electrons which
transfer heat through random
movements of the free electrons besides
transferring heat through the vibrations
of atoms in the lattice structure.
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3.  ii) Why diamond have a high thermal
conductivity?
 Answers: This is because the
arrangement of atoms in diamond is very
compact. Therefore, the transfer of heat
through the vibrations of atoms can
happen very fast.
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4.  b) Table shows the thermal conductivity of
aluminium, steel, copper and lead.
 i) Which metal is the most effective when used to make
the cooling fins of a refrigerator or car radiator?
 Answer: Copper
 ii) Explain why the cooling fins must have a large surface
 area?
 Answer: A large surface area increases the rate of heat
loss
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Metal Thermal Conductivity/
W m-1 K-1
Aluminium 235
Steel 14
Copper 401
Lead 35