Eddy-current speedometers

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In summary, the conversation is about a student's physics practical coursework on investigating the relationship between the rate of revolution of a permanent magnet and the turning force induced in a metal cup or plate in an eddy-current speedometer. The student is looking for equations and calculations to prove their expected results and mentions knowledge of electromagnetic induction and Lenz's Law. They are at the sixth form level and have a good understanding of single-variable calculus. They are unsure of how to use the equations to obtain numerical answers in this context and need help relating revolutions per second to force.
  • #1
jamhar89
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For my physics practical coursework I investigated how the rate of revolution of the permanent magnet in an eddy-current speedometer affects the turning force induced in the metal cup or plate.

I got the results I expected, and I am required to prove them using appropriate equations and calulations. Does anyone have any idea of which equations are relevant to this application?

Any help would be greatly appreciated!
 
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  • #2
What level are you at: high school, introductory college/university, or intermediate college/university? What level of math: algebra only, single-variable calculus, multivariable (vector) calculus?

Do you have a textbook available to you as part of the course? What sort of material does it have about electromagnetic induction and Lenz's Law?
 
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  • #3
im at sixth form, so just before university. i do a fair bit of calculus, mainly single variable. I know about lenz's law and faraday's law, induction and all that, and that they have some relevence, I just don't see how they can be used for calculations to get numerical answers in this context. Basically, I need to relate revolutions per second to force
 

1. What is an eddy-current speedometer?

An eddy-current speedometer is a type of speedometer found in many modern cars. It uses a magnet and a metal disc to measure the speed of the vehicle.

2. How does an eddy-current speedometer work?

The eddy-current speedometer works by using a magnet attached to the speedometer cable, which rotates as the car moves. This magnet creates a magnetic field that interacts with a metal disc in the speedometer, causing eddy currents to form. The strength of these currents is directly proportional to the speed of the vehicle, and the speedometer needle is calibrated to display the correct speed based on the strength of the currents.

3. What are the advantages of using an eddy-current speedometer?

One advantage of using an eddy-current speedometer is its accuracy. Since it relies on magnetic fields and currents rather than mechanical components, it is less prone to wear and tear and can provide a more precise reading. Additionally, eddy-current speedometers tend to have a longer lifespan compared to traditional mechanical speedometers.

4. Are there any limitations to using an eddy-current speedometer?

One limitation of eddy-current speedometers is that they can be affected by external magnetic fields. This can cause inaccuracies in the speed reading. Additionally, eddy-current speedometers may not work properly if there is a problem with the magnet or metal disc, requiring repairs or replacements.

5. Can eddy-current speedometers be used in all types of vehicles?

Eddy-current speedometers are commonly used in cars, but they can also be found in motorcycles and other vehicles. However, they may not be suitable for use in vehicles that operate in extreme temperatures or in environments with high levels of electromagnetic interference, as this can affect their accuracy.

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