So the strong magnetic pole is n pole;
(2) The stress analysis of the circular ring can be equivalent to a straight steel wire, and the vertical direction is as follows
Mg=F amp cos60 = BILcos60;;
Ring circumference l = 2πr = 0.8m;;
Substituting the above formula can get b = 25t.
Therefore, the magnetic induction intensity at the ring is 25T;;
(3) The descending process of the ring is governed by the law of conservation of energy.
mgh = I2Rt = I2ρlSt;
Substitute data ρ= 1.25× 10-4ω? m;
Therefore, the resistivity of superconducting ring is about 1.25× 10-4ω? m;
Answer: (1) The strong magnetic pole is N pole;
(2) The magnetic induction intensity at the ring is 25T;;
(3) The resistivity of superconducting ring is about 1.25× 10-4ω? Meter (short for meter))