P2

Question 1

What does it mean if the thermal conductivity of a material is greater

Answer 1

The more energy per second it transfers by conduction

Question 2

In the winter, do you need high or low thermal conductivity and why

Answer 2

Low so that energy transfers through them as low as possible therefore the heat stays in your home

Question 3

3 things energy transfers per second through a layer of insulating material depends on…

Answer 3

Temp difference across the material, thickness of the material and thermal conductivityness of the material

Question 4

How do you reduce the energy transfers as much as possible

Answer 4

Thermal conductivity should be as low as possible and thickness of the insulating layer should be as thick as possible

Question 5

5 best heat conductors

Answer 5

Copper, aluminium, graphit, silver and gold

Question 6

What is specific heat capacity

Answer 6

Amount of energy needed to raise the temperature of 1kg of a substance by 1^C

Question 7

If a material needs to increase their temperature, what does it require?

Answer 7

More energy to be transfered to the thermal energy store

Question 8

Equation for specific heat capacity

Answer 8

/\ E = mc/\temp
Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg°C)x temperature changr

Question 9

What is specific heat capacity

Answer 9

The amount of energy needed to raise the temperature of 1kg of a substance by 1°C

Question 10

Equipment list for specific heat capacity practical

Answer 10

Power supply, ammeter, thermometer, insulation, block of material, voltmetter, wires, heat supply

Question 11

What does insulation reduce

Answer 11

The rate of energy transfers by heat

Question 12

What can someone do to insulate their homes

Answer 12

• thick walls that are made from a low thermal conductivity material
• loft insulation. Because hot things rise, a lot of heat is lost through the roof so if it is insulated them heat would stay in the house
• double glazed windows

Question 13

Coservation of energy principle:

Answer 13

Energy can be transferred, stored or dissipated, it can never be created or destroyed

Question 14

What is an example of energy being dissipated?

Answer 14

A mobile phone when fully charged. Energy is usefully transferred from the chemical energy store if the battery of the phone. But some energy is dissipated in this tranfer to the thermal energy store

Question 15

How does lubrication reduce frictional forces?

Answer 15

They can flow easily between objects and coat them so that the objects slide over eachother

Question 16

How do cavity walls work?

Answer 16

Made up of an inner and outer wall, with an air gap in the middle. The air gap reduces energy transfer by conduction as it slows the process down

Question 17

How does loft insulation work?

Answer 17

Energ always rises so loft insulation can reduce convection currents

Question 18

How do double glazed windows work?

Answer 18

They have an air gap between two sheets of glass to prevent energy transfer by conduction

Question 19

How are devices useful?

Answer 19

If they tranfer energy from one store to another

Question 20

How is a device efficent?

Answer 20

When less energy is wasted

Question 21

How can you improve efficiency?

Answer 21

Insulating objects or lubricating them. Making them streamlined

Question 22

Where does all energy end up?

Answer 22

To the thermal energy store

Question 23

Example of energy being transferred to thermal energy store

Answer 23

Electric drill