There is a magnetic material of coercivity 2 x 10³ A/m. What current should flow through a solenoid of length 15 cm having 150 turns to demagnetize the substance completely?
Correct answer: C. 2 A
- A. 4 A
- B. 2.5 A
- C. 2 A
- D. 3.5 A
Explanation
The magnetic field strength (H) inside a solenoid is H = nI, where n is the number of turns per unit length. Here, n = 150 turns / 0.15 m = 1000 turns/m. To demagnetize the material, the solenoid's field must equal the coercivity: 2 x 10³ A/m = (1000 turns/m) × I, which gives I = 2 A.
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