Angle: the structure and principles of magnet according to the principle of refraction, arc material effect is best, right Angle refraction material loss is bigger.
Space: the lines of magnetic force in the air like a mobile phone signal, it is necessary to have a space to reflect.
Flashlight lamp on the pot as completely wrapped in lamp, the use of magnet effect is bad, because there are a lot of light refraction was loss.
The selection of materials: materials and thickness, and the magnet and the spacing of materials have a close relationship.
Pure iron easy leakage, refraction increased after special treatment, but 100% of shielding materials haven't worked out, but different factory has the different effect.