The distance at which magnet can attract

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Discussion Overview

The discussion centers around the feasibility of one magnet attracting another over a distance of 1 meter, exploring the conditions under which this attraction occurs, the size and type of magnets required, and the nature of the force involved. It includes theoretical considerations and challenges related to magnetic attraction and its diminishing effects over distance.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether a magnet can attract another over a distance of 1 meter and if they could be bound together at that distance.
  • Another participant asserts that it is indeed possible for magnets to attract each other over that distance.
  • There is a query regarding the size of the magnet needed and whether it should be an electromagnetic type.
  • One participant explains that while magnets attract each other from any distance, the force diminishes with distance, specifically noting that doubling the distance results in a fourfold decrease in attraction force.
  • Another participant challenges the accuracy of the fourfold decrease, suggesting it might be eight times less, and discusses the relationship between distance and force decay.
  • Further clarification is provided that the force diminishes with the cube of the distance at larger separations, indicating that doubling the distance results in an eightfold decrease in force.
  • Some participants express skepticism about the portrayal of magnets in movies, suggesting that such representations often involve bad science.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the specifics of how the force of magnetic attraction decreases with distance, with some asserting a fourfold decrease and others suggesting an eightfold decrease or a cubic relationship. The discussion remains unresolved on these points.

Contextual Notes

There are assumptions regarding the orientation of the magnet poles and the conditions under which the attraction is considered. The discussion also reflects varying interpretations of the mathematical relationships governing magnetic forces over distance.

alaindvs
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Is it possible for one magnet to attract another over a distance of 1m? To specify, if magnet 1 was at point A on the East side of the ruler, and magnet 2 was stationary at point B on the West side of the ruler. Could magnet 2 attract magnet 1 so much that both were bound together at point B on the West Side of the Ruler?
 
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Yes, it is.
 
what size of magnet would i need? and would it have to be electromagnetic
 
Sure. In fact, assuming the poles are oriented correctly, the magnets already attract each other from any distance. The force of the attraction falls off at a distance though. If you double the distance the attractive force decreases by 4x. So after a bit the force can no longer overcome friction. This is why magnets don't usually go flying across the room to another one.
 
Drakkith said:
If you double the distance the attractive force decreases by 4x
Ooouch? Are you quite sure that number? Maybe rather 8?
 
xts said:
Ooouch? Are you quite sure that number? Maybe rather 8?

I didn't think so. It falls off with the square root correct? Doubling the distance is 4 times less, quadrupaling the distance would be 16 times less, and etc right?
 
Put a REALLY big magnet at B and a light one at A :smile:
 
Drakkith said:
I didn't think so. It falls off with the square root correct? Doubling the distance is 4 times less, quadrupaling the distance would be 16 times less, and etc right?

So when you have seen in a movie the bad evil guy using his super ultra magneto-gizmo weapon it usually is bad science.
 
It falls off with the square root correct?
Not quite correct. At larger distances (comparing to magnet size) falls with [itex]1/d^3[/itex]. Doubling the distance makes 8 times smaller force.
Guess why?
 
  • #10
xts said:
Not quite correct. At larger distances (comparing to magnet size) falls with [itex]1/d^3[/itex]. Doubling the distance makes 8 times smaller force.
Guess why?

Ah ok. I must have been thinking in 2d. :biggrin:

So when you have seen in a movie the bad evil guy using his super ultra magneto-gizmo weapon it usually is bad science.

Usually yes. Although it depends on the circumstances in the film.
 

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