A) 8 A
B) 6 A
C) 4.5 A
D) 2 A
Correct Answer: A
Solution :
The reversed magnetic field needed to demagnetise the specimen is known as coercivity of the material. \[B={{\mu }_{0}}H\] or \[{{\mu }_{0}}ni={{\mu }_{0}}H\] or \[\frac{Ni}{L}=H\] \[\left( \because n=\frac{N}{L} \right)\] or \[i=\frac{HL}{N}\] Given, \[H=4\times {{10}^{3}}A{{m}^{-1}},\] \[L=12\text{ }cm=12\times {{10}^{-2}}m,\text{ }N=60\text{ }turns\]. Substituting the values, we get \[i=\frac{4\times {{10}^{3}}\times 12\times {{10}^{-2}}}{60}=8A\]
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