Physics chapter 11

Question 1

name 3 ways thermal energy is transfered?

Answer 1

Conduction, Convection, and radiation

Question 2

Define conduction?

Answer 2

The process by which thermal energy is transmitted through a medium from one particle to another

Question 3

When does Thermal energy transfer stop?

Answer 3

When both particles are the same tampature.

Question 4

Why is the conduction of thermal energy better in metals compared to other solids?

Answer 4

It is because the thermal energy is transmitted through both the vibrating molecules and the free electrons.

Question 5

Why is a vacuum a perfect insulator?

Answer 5

It is a perfect insulator because conduction cannot occur when there are no particles present

Question 6

Why are gas a liquids poor heat conductors?

Answer 6

Because the particles are far apart.

Question 7

What is a material that does not conduct heat called?

Answer 7

An insulator

Question 8

Define convection?

Answer 8

It is the process by which thermal energy is transmitted from one place to another by the movement by the movement of heated particles of a gas or liquid.

Question 9

What happens to the density of air when it is heated?

Answer 9

It decreases

Question 10

Define convection current?

Answer 10

When hot liquid/gas floats due to lower density its place is taken by the falling cold and denser gas/liquid. The cold gas/liquid is then heated and floats up.

Question 11

Define radiation?

Answer 11

The transfer of thermal energy by electromagnetic waves.

Question 12

Why can radiation take place in a vacuum?

Answer 12

Because it does not need a medium to transfer thermal energy.

Question 13

What is the source of thermal energy is radiation?

Answer 13

Infra-red raditation

Question 14

How do the light from the sun and other stars reach us?

Answer 14

It gets to us in the form of electromagnetic radiation.

Question 15

How does infra-red radiation travel?

Answer 15

It travels in a straight line

Question 16

Dull-black surface qualities?

Answer 16

They are very good absorbers and emitters of heat

Question 17

Silver/white surface qualities?

Answer 17

They are poor absorbers and emitters` of heat.

Question 18

Factors that affect the rate of radiation?

Answer 18

1. The type of surface - Black surface cools faster through radiation
2. The temperature of the surface - A hotter surface radiates energy at a greater rate
3. The surface area - Energy is radiated at a greater rate from a bigger surface area

Question 19

What is the rate of energy escaping from us?

Answer 19

100 J/s

Question 20

Methods of insulating a house?

Answer 20

1. Thick curtains (To prevent heat from escaping and cold from entering?
2. Loft and underfloor insulating material (Prevents conduction of heat through floors and ceiling)
3. Double and triple glazing of windows (Vacuum between the panels helps prevent heat loss from conduction and convection)
4. Cavity walls ( Reduces heat loss through conduction)
5. Foam in wall cavity (Reduces heat loss through convection)