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Edexcel IGCSE Physics B Energy Transfers Questions

Practise tracing energy stores and transfer pathways, using efficiency data, Sankey diagrams, and thermal transfer models in real device contexts.

Syllabus
First assessment 2019
Course
Physics 4PH1

Exam points

  • describe store changes and transfer routes for springs, batteries, winches, solar panels and ramps
  • use conservation and efficiency ideas to account for useful output, wasted energy and thermal stores
  • explain conduction, convection and radiation using particles, density changes and surface colour

Covered syllabus points

4.2 Energy stores and transfers4.3 Conservation of energy4.4 Efficiency equation4.5 Energy transfer devices4.6 Thermal energy transfer4.7 Convection4.8 Radiation emission and absorption4.9 Thermal transfer practical4.10 Reducing unwanted energy transfer

Question 1

[Maximum number: 3]

A student stretches a rubber band.

Question (a)

(a)

The photographs show a rubber band before and after it has been stretched.

before

before

after

after

[ 3 ]

Question (i)

(i)

State which energy store increases in the rubber band after it has been stretched.

[ 1 ]

Question (ii)

(ii)

State the main method of energy transfer when the rubber band is stretched.

[ 1 ]

Question (iii)

(iii)

State the source of the energy transferred to the rubber band.

[ 1 ]

Question 2

[Maximum number: 9]

The photograph shows a toy car. When the toy car is pulled backwards, energy is stored in the elastic store as the rubber band is twisted.

Figure for Question 2 — Edexcel IGCSE Physics

When the car is released, some of the energy from the elastic store is transferred to the kinetic store of the car.

The remaining energy is transferred into the thermal store of the surroundings.

Question (a)

(a)

State what is meant by the principle of conservation of energy.

[ 1 ]

Question (b)

(b)

The car is pulled backwards so that there is 165 J of energy in its elastic store.

When the car is released, this energy is transferred to the car's kinetic energy store with an efficiency of 15\%.

[ 8 ]

Question (i)

(i)

State the formula linking efficiency, useful energy output and total energy output.

[ 1 ]

Question (ii)

(ii)

Calculate the energy transferred into the thermal store of the surroundings.

energy transferred to thermal store = ............ J

[ 4 ]

Question (iii)

(iii)

Draw a labelled Sankey diagram for this energy transfer.

[ 3 ]

Question 3

[Maximum number: 3]

A student uses this apparatus to investigate how the efficiency of an electric motor varies with its input voltage.

Figure for Question 3 — Edexcel IGCSE Physics

This is the student's method.
- connect the electric motor to a d.c. power supply and a joulemeter
- attach a 1.0 kg mass to the electric motor using a length of string
- set the voltage of the power supply to 10 V and switch on the power supply
- switch off the power supply when the mass has been lifted through a distance of 50 cm
- record the input energy to the motor from the joulemeter
- calculate the energy transferred to the gravitational store of the mass
- calculate the efficiency of the motor

The student repeats this process, setting the power supply to a different voltage each time.

The table shows the student's results.

Table for Question 3 — Edexcel IGCSE Physics

Calculate the motor efficiency when the power supply is set to a voltage of 10 V.

efficiency = ............ %

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