A magnetic needle suspended parallel to a magnetic field requires 
J of work to turn it through 60 ° . The torque needed to maintain the needle in this position will be:
A
B
3J
C
D
Text Solution
Verified by ExpertsThe correct answer is:
B
Work done in changing the orientation of a magnetic needle of magnetic moment M in a magnetic field 
from position 
to 
is given by
Here, 
… ..(i)
The torque on the needle is
In magnitude,
Dividing (ii) by (i), we get
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