1.2.1 And 1.2.2 Energy Transfers In A System And Efficiency

Question 1

Ways that energy can used

Answer 1

• Transferred
• Stored
• Dissipated

Question 2

Energy transfer when a light switch is switched on

Answer 2

• Chemical energy is transferred to light energy
• Some energy is wasted as thermal energy

Question 3

Conductor

Answer 3

Material that transmits energy very well- it has a high thermal conductivity

Question 4

Insulator

Answer 4

Material that doesn’t transmit energy well- it has a low thermal conductivity

Question 5

Conduction

Answer 5

The transfer of energy, such as heat or an electric charge, though a substance

Question 6

Radiation

Answer 6

The transfer of energy through waves or particles

Question 7

Energy transfer in a closed system - adding iced cubes to a water bottle (2p)

Answer 7

• assuming the water bottle doesn’t allow an energy exchange with the surroundings
• Thermal energy is exchanged from the water to the ice cubes, so the water will cool down

Question 8

Ways to reduce unwanted energy transfer (3p)

Answer 8

Lubrication
Thermal insulation
Streamlining

Question 9

Lubrication

Answer 9

To reduce friction and therefore reduce energy loss

Question 10

Thermal insulation

Answer 10

To reduce heat leaving a house and can include double glazed windows

Question 11

Streamlining

Answer 11

Reduces air resistance and therefore reduces energy loss

Question 12

Ways to heat a home (5p)

Answer 12

• use material with a low thermal conductivity
• loft insulation
• hot water tank jackets
• double glazing
• thick curtains

Question 13

How is the rate of cooling affected by the thickness and thermal conductivity of its walls? (2p)

Answer 13

• thicker walls slow down heat transfer
• materials with a low thermal conductivity slow down rate if energy transfer

Question 14

Efficiency equation

Answer 14

Useful power output ÷ total power output