Age range: 14-16
Duration: 0 - 29 mins
  • Maths

Fault detectors using circles

Organise mathematical information to choose the optimum size for a 'fault detector' coil

A company has invented a system to find defects in hot steel bars. The hot cylindrical bar must pass through a defect detector which is shaped like a ring. To work properly the bar must fill between 60 to 80% of the area inside the detector ring.

Activity info, teachers' notes and curriculum links

An engaging activity in which students will use the GeoGebra file to measure the size of the defect in hot steel bars produced by the company.

The activity sheet includes teacher notes, guidance, useful web links, and links (where appropriate) to the national curriculum in each of the four devolved UK nations; England, Northern Ireland, Scotland and Wales.

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All activity sheets and supporting resources are free to download, and all the documents are fully editable, so you can tailor them to your students' and your schools' needs.

The related GeoGebra file for this activity can be viewed at the following link:


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Activity overview

Fault detectors using circles activity description, teachers' notes and curriculum links.



Help the company to find any defects in their hot steel bars using the fault detection system.

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