(1) Because the heat source for cooking in the induction cooker comes from the cooker itself instead of the induction cooker itself, the heat loss is reduced, so the thermal efficiency of the induction cooker is higher.

(2) Current during normal operation:

I = PU = 2000 w220v≈9. 1A；

(3) Heat absorbed by water:

q = cm(t 1-T2)= 4.2× 103j/(kg？ ℃)× 1kg×( 100℃-25℃)= 3. 15× 105j，

Electric energy consumed by heating water:

w = Pt = 2000 w× 175s = 3.5× 105j，

Thermal efficiency of induction cooker:

η=Q absorption w = 3.15×105j3.5×105j = 90%.

Answer: (1) Compared with ordinary electric furnaces, induction cookers have higher thermal efficiency;

(2) The current during normal operation is about 9.1a; ;

(3) The power consumption is 3.5× 105J, and the thermal efficiency of the induction cooker is 90%.