Edexcel IGCSE Physics 4.5 energy transfer devices

Practise Sankey diagram questions by splitting input energy into useful and wasted outputs and using the given efficiency to scale arrows.

Exam points

Draw a Sankey diagram with one input arrow and separate useful and wasted output arrows.
Use the given efficiency to scale useful and wasted arrows in a labelled diagram.

[Maximum number: 3]

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 4.5 Energy transfer devices question 1 — 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.

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\%.

Draw a labelled Sankey diagram for this energy transfer.

diagram to show standard single input with two output arrows; input and output arrows labelled correctly;

scale approximately correct;

e.g.

Figure for Answer to Question 4.5 Energy transfer devices question 1 — Edexcel IGCSE Physics

arrows can be in any orientation e.g. both useful and wasted arrows
drawn horizontally
allow
elastic, input, total for initial arrow kinetic, useful (output) for narrower output thermal/heat, wasted (output) for wider output but apply ECF from (b)(ii)
allow ECF from (b)(ii)
judge by eye - wasted arrow should
be at least $4 \times$ wider than useful
arrow and they should sum to
approximately the width of the
input

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4.5 Energy transfer devices question 1