Chapter 1.4 - 'Conduction'

Question 1

State the three means of heat transfer.

Answer 1

1. Conduction.
2. Convection.
3. Radiation.

Question 2

Define a good conductor.

Answer 2

A material that can conduct heat readily.

Transfers heat faster

Question 3

Define a good insulator.

Answer 3

A material that cannot conduct heat readily.

Transfers heat slower

Question 4

List the ways in which conduction can occur.

Answer 4

1. Energy transfer through molecular or atomic collisions.

2. Energy transfer by free electrons.

Question 5

State which materials are mostly able to transfer heat through ‘free electrons’ and why.

Answer 5

Metals, as the electrons are only slightly attracted to their nuclei. This allows freer moving electrons to carry the energy.

Question 6

Define ‘Thermal Conductivity’.

Answer 6

The ability of a material to conduct heat.

Question 7

State the symbol of ‘Thermal Conductivity’

State the unit of ‘Thermal Conductivity’

Answer 7

k

W/mK

Watts per metre Kelvin

Question 8

List the factors affecting the speed of thermal conduction.

4 things

Answer 8

1. Thermal conductivity of material - The higher the more conductive.
2. Temperature difference between the two objects - The greater temperature difference the faster the rate of energy transfer.
3. Thickness of material - The thicker the slower.
4. Surface area - The larger the surface area the higher the speed.

Question 9

Explain why Igloos keep in heat?

Answer 9

The snow is made up of many compressed air pockets, as air is a poor conductor of heat the heat inside is not transferred away as easily.

Question 10

State how energy transfer via conduction is measured per unit time?

Answer 10

Q/t = (kAδT)/L

Heat (J) over time (s) is equal to thermal conductivity (W/mK) to the surface area (m^2) to the change in temperature (K) over thickness (m)