Reducing unwanted energy transfers

Question 1

Whenever something move, what force is acting against it ? EXAMPLE

how can this force be reduced ?

Answer 1

There’s always at least one frictional force acting against it.
This causes some energy in system to be dissipated . Example= air resistance transfer energy from falling object’s kinetic energy store to TES .

For objects rubbed together, lubricants can be used to reduce frictional forces between object’s surfaces when they move. Lubricants are usually liquids and flow easily between objects and coat them.

Question 2

What is conduction ?

Answer 2

When an object is heated, energy is transferred to KES of particles. This causes particles to vibrate more and collide with each other. During these collisions, energy is transferred between particles kinetic energy store = conduction

Question 3

Thermal conductivity is a measure of ..

Answer 3

measure of how quickly energy is transferred through a material in a conductive way.
Materials with higher thermal conductivity transfer energy between particles at a faster rate.

Question 4

What is convection ?

Answer 4

If particles are free to move, the particles moving faster means the space between each individual particle increases. This causes the density of the region being heated to decrease.

Because liquids and gases can flow, the warmer and less dense region will rise above denser, cooler region. So energetic particles move away from hotter to cooler regions = convection

Question 5

Prevent energy losses through heating - houses

Answer 5

• Thick walls made from material with low thermal conductivity. Thicker the wall, lower thermal conductivity = slower rate of energy transfer.

Use thermal insulation

Question 6

Examples of thermal insulation

Answer 6

1) cavity walls, made up of a inner and outer wall with air gap in middle. Air gap reduces the amount of energy transferred by conduction through walls.

2) cavity wall insulation where cavity wall gap filled with foam reduces energy transfer by convection in the wall cavity.

3) loft insulation can reduce convection currents ( where air particles are constantly heated ) being created in lofts

4) Double glazed window works the same way as cavity walls - air gap in between two sheets of glass to prevent energy transfer by conduction through window

5) Draught excluders around doors and windows reduce energy transfer by convection