Strength of magnetic field to attract Iron blocks

[dabeliking]

Hi everyone. I have a simple doubt related to magnetism and inspired by the Bollywood movie 'ROBOT' staring Rajnikant.

In the spectacular chase scene where Chitti(the robot) is trapped on a bridge with Aishwarya Rai( the heroine of the movie) and are surrounded by multitudes of policemen, he then turns on some sort of electromagnet and attracts all the guns towards him. The guns are pulled out of the hands of the police men and come flying and stick to his body. How he fires them is a different story but my question is what must be the strength of magnetic field to attract say about 40 machine guns weighing ~10kg each (400kg total) at a distance of ~25 meters or so (the distance is approximate)?
Some considerations: 1) Magnetic field decreases exponentially from a source, so 'Chitti's' magnetic field must be quite high. 2) Since Chitti doesn't use his magnetic field always. it means it runs on an electromagnet. So once the magnetic field strength is calculated to yank out 400kg of iron from a distance of 25 meters, next question would be what is the current required to get that sort of magnetic field?

This is just a curious question that popped in my mind. Thanks for seeing.
The movie scene is here ( http://www.youtube.com/watch?feature=player_detailpage&v=yysbbPStfWw#t=84s )

Cheers

 

[Vailanor]

,Sarath.To answer your question, the strength of the magnetic field required to attract 40 machine guns weighing ~10kg each (400kg total) at a distance of ~25 meters would depend on several factors, including the type of material the guns are made of, the size and shape of the guns, and the distance between the guns and the source of the magnetic field. In general, the magnetic field strength increases with the distance from the source of the magnetic field, so the closer the guns are to Chitti, the higher the magnetic field strength will need to be. Additionally, the stronger the material that the guns are made of, the higher the magnetic field strength will need to be. To get a rough estimate of the magnetic field strength needed, we can use the equation B = μo*(N*I)/2πr, where B is the magnetic field strength, μo is the permeability of free space, N is the number of turns in the electromagnet, I is the current passing through the electromagnet, and r is the distance between the guns and the electromagnet. Assuming that the guns are made of iron and that the electromagnet is cylindrical, we can estimate that the magnetic field strength required to attract the guns would be somewhere in the range of 0.1-0.2 Tesla. The exact magnetic field strength required would depend on the exact distance between the guns and the electromagnet. The current required to produce a 0.1 Tesla magnetic field in an electromagnet depends on the number of turns in the electromagnet. Assuming the electromagnet has 100 turns, the current needed to produce a 0.1 Tesla magnetic field would be approximately 8 Amps.