# The distance at which magnet can attract

1. Aug 4, 2011

### alaindvs

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?

2. Aug 4, 2011

Yes, it is.

3. Aug 4, 2011

### alaindvs

what size of magnet would i need? and would it have to be electromagnetic

4. Aug 4, 2011

### Staff: Mentor

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.

5. Aug 4, 2011

### xts

Ooouch? Are you quite sure that number? Maybe rather 8?

6. Aug 4, 2011

### Staff: Mentor

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?

7. Aug 4, 2011

### phinds

Put a REALLY big magnet at B and a light one at A

8. Aug 4, 2011

### 256bits

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

9. Aug 4, 2011

### xts

Not quite correct. At larger distances (comparing to magnet size) falls with $1/d^3$. Doubling the distance makes 8 times smaller force.
Guess why?

10. Aug 4, 2011

### Staff: Mentor

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

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