Print all · Topic 4

Energy Transfers — all three papers

Pearson Edexcel International GCSE

Physics — Topic 4 Paper 1

Energy resources and energy transfers · specification 4.1–4.17

Time allowed: 30 minutes

Total marks: 25

Candidate name:

Centre / class:

Answer all questions. You may use a calculator. Show your working. Take $g=10\,\text{N/kg}$.

1

The Sankey diagram for an electric kettle is labelled $2000\,\text{J}$ input, $1600\,\text{J}$ useful thermal energy transferred to the water, and $400\,\text{J}$ wasted.

(a) Calculate the efficiency of the kettle.

[2]

(b) State the useful energy store that increases and the pathway by which energy is transferred to the kettle.

[2]

(c) Name the store that decreases to supply the $2000\,\text{J}$, and state where the wasted $400\,\text{J}$ goes.

[2]

(Total for Question 1 = 6 marks)

2

A brick of mass $2.0\,\text{kg}$ is held at rest $5.0\,\text{m}$ above the ground.

(a) Calculate the gravitational potential energy store of the brick relative to the ground.

[2]

(b) The brick is dropped. Air resistance is negligible. State the kinetic energy just before it hits the ground and calculate its speed.

[3]

(c) In a second drop, work done against friction is $20\,\text{J}$. Calculate the kinetic energy just before impact.

[2]

(Total for Question 2 = 7 marks)

3

A student uses a vacuum flask to keep tea hot. The flask has a double silvered wall with a vacuum between the walls, and a plastic stopper.

(a) Explain how the vacuum reduces thermal energy transfer from the tea.

[2]

(b) Explain how the silvering reduces thermal energy transfer.

[2]

(c) Explain the purpose of the stopper.

[2]

(Total for Question 3 = 6 marks)

4

A student investigates how the surface of an object affects the infrared radiation it emits. She uses a Leslie’s cube filled with very hot water. The four faces have different surfaces, including dull black and shiny silver.

(a) Describe a method the student should use to compare the radiation from two faces. Include what she measures and what she keeps the same.

[4]

(b) Suggest two sources of error in this investigation and how one of them could be reduced.

[2]

(Total for Question 4 = 6 marks)

END OF PAPER 1

Pearson Edexcel International GCSE

Physics — Topic 4 Paper 2

Energy resources and energy transfers · specification 4.1–4.17

Time allowed: 30 minutes

Total marks: 25

Candidate name:

Centre / class:

Answer all questions. You may use a calculator. Show your working. Take $g=10\,\text{N/kg}$.

1

A filament lamp is supplied with $60\,\text{J}$ of electrical energy. $12\,\text{J}$ is transferred usefully as light. $48\,\text{J}$ is wasted as thermal energy.

(a) Calculate the efficiency of the lamp.

[2]

(b) On a Sankey diagram, which arrow should be the widest: the input, the useful output, or the wasted output? Explain your answer.

[2]

(c) Name the pathway for the useful transfer and the store that increases because of the wasted $48\,\text{J}$.

[2]

(Total for Question 1 = 6 marks)

2

A skateboarder of mass $50\,\text{kg}$ starts from rest at a height of $3.2\,\text{m}$ above the bottom of a ramp.

(a) Calculate the gravitational potential energy store at the top of the ramp.

[2]

(b) On the way down, friction transfers $400\,\text{J}$ to the thermal store of the wheels and air. Calculate the kinetic energy at the bottom.

[2]

(c) Calculate the speed of the skateboarder at the bottom.

[3]

(Total for Question 2 = 7 marks)

3

A room is heated by an electric heater placed on the floor near one wall.

(a) Explain how a convection current is set up in the room. Refer to density in your answer.

[4]

(b) Suggest why the heater is placed near the floor rather than on the ceiling.

[2]

(Total for Question 3 = 6 marks)

4

A student compares how well different metals conduct thermal energy. She uses rods of copper, aluminium and iron. A drawing pin is attached to the end of each rod with wax. The other ends are heated together.

(a) Describe a method the student should use. State the independent variable, the dependent variable, and two quantities she must control.

[4]

(b) State one safety precaution and one reason a pin might fall at the wrong time, giving a false result.

[2]

(Total for Question 4 = 6 marks)

END OF PAPER 2

Pearson Edexcel International GCSE

Physics — Topic 4 Paper 3

Energy resources and energy transfers · specification 4.1–4.17

Time allowed: 30 minutes

Total marks: 25

Candidate name:

Centre / class:

Answer all questions. You may use a calculator. Show your working. Take $g=10\,\text{N/kg}$.

1

An electric motor is supplied with $800\,\text{J}$ of energy. $600\,\text{J}$ is transferred usefully to the kinetic store of a flywheel. $200\,\text{J}$ is wasted as thermal energy.

(a) Calculate the efficiency of the motor.

[2]

(b) State the principle of conservation of energy and use it to show that the figures on the Sankey diagram add up correctly.

[2]

(c) Name the pathway that transfers energy to the motor and the store that increases because of the wasted $200\,\text{J}$.

[2]

(Total for Question 1 = 6 marks)

2

A roller-coaster car and passengers have a combined mass of $80\,\text{kg}$. The car is released from rest at a height of $12\,\text{m}$. At the bottom of the first drop the kinetic energy is $7200\,\text{J}$.

(a) Calculate the gravitational potential energy store at the top.

[2]

(b) Calculate the work done against friction on the way down.

[2]

(c) Calculate the speed of the car at the bottom.

[3]

(Total for Question 2 = 7 marks)

3

A house has cavity walls filled with foam and double-glazed windows.

(a) Explain how cavity-wall foam reduces the rate of thermal energy transfer through the wall.

[3]

(b) Explain how double glazing reduces thermal energy transfer through the window.

[3]

(Total for Question 3 = 6 marks)

4

A teacher demonstrates convection using a large beaker of water, a crystal of potassium permanganate and a small Bunsen flame. A heater in a tank of water could be used instead.

(a) Describe a method to show a convection current. State what you would see.

[4]

(b) Explain, in terms of density, why the coloured water moves as it does. State one safety precaution.

[2]

(Total for Question 4 = 6 marks)

END OF PAPER 3