A) 8 A
B) 6 A
C) 4.5A
D) 2 A
Correct Answer: A
Solution :
The reversed magnetic field needed to demagnetize , the specimen is known as coercivity of the material. \[=1\times \frac{\pi }{4}-\int_{0}^{\pi /4}{\tan y\,dy=\frac{\pi }{4}+[\log \,\cos \,y]_{0}^{\pi /4}}\] \[=\frac{\pi }{4}+[\log \,\cos \,y]_{0}^{\pi /4}\] \[=\frac{\pi }{4}+\log \,\cos \frac{\pi }{4}-\log \cos 0=\frac{\pi }{4}+\log \frac{1}{\sqrt{2}}-\log 1\] \[=\frac{\pi }{4}+\log 1-\log \sqrt{2}-\log \,\,1=\frac{\pi }{4}+\log \frac{1}{\sqrt{2}}-\log 1\] \[=\frac{\pi }{4}+\log 1-\log \sqrt{2}-\log \,\,1=\frac{\pi }{4}+0-\sqrt{2}-0\] \[=\left( \frac{\pi }{4}-\log \sqrt{2} \right)sq\,units\]
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