For many years engineers have used the braking effect of eddy currents in a variety of situations, including trains and rollercoasters. As there is no physical contact in such a brake, these devices do not suffer from frictional wear. The braking effect is a very clear demonstration of Lenz’s law and so is often demonstrated in physics lessons.
This question explores the essential physics of eddy current braking. It is question 3 from OCR Physics B Paper H577/01, June 2019, and is reproduced by kind permission of OCR. We will present solutions to all three parts of the question but concentrate on discussing students’ responses to parts (a) and (b), as these provide interesting examples of questions requiring explanatory answers. The answers that follow are the responsibility of Physics Review, and have neither been provided nor approved by OCR.
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