Question

There is magnetic material of coercivity 2 × 10³ A/m. What current should flow through solenoid of length 15 cm having 150 turns to demagnetise the substance completely?

• A. 4 A
• B. 2.5 A
• C. 2 A
• D. 3.5 A

Answer 1

Answer: (C)

2 A

Answer 2

H = 2 × 10³, for solenoid H = n i

n = $\frac { 150 } { 15 \times 10 ^ { - 2 } }$= 1000 ⇒i =$\frac { 2 \times 10 ^ { 3 } } { 10 ^ { 3 } }$ = 2A