(20 13? Mianyang) The superconducting current limiter developed at present has zero resistance when the current is less than a certain value; When the current is greater than a certain value, its resi

(20 13? Mianyang) The superconducting current limiter developed at present has zero resistance when the current is less than a certain value; When the current is greater than a certain value, its resistance is a certain value. (1) As can be seen from Figure A, when the loop current I 1=30A, the resistance of the superconducting current limiter is zero.

The voltage m across the electrical appliance is equal to the power supply voltage, so the power of the electrical appliance is:

p = ui 1 = 5× 104v×30A = 1.5× 106 w；

(2) When M is short-circuited, the voltage across the current limiter is equal to the power supply voltage,

In order to protect the circuit, the resistance of the current-limiting resistor should not be zero, and the minimum circuit current should be 50A.

∫I = UR，

The ∴ resistance value of the current limiting resistor r0 = ui2 = 5×104v50a =1000ω;

Answer: (1) The electric power consumed by electrical appliance M is1.5×106 W;

(2) The resistance of superconducting current limiting resistor should not be greater than1000Ω.