A Basic Magnetic Problem
Electricity and Magnetism
Level
2
A wire carries steady current. It is first bent to form a circular plane coil of one turn. The same length is now bent to give a double loop of smaller radius. The magnetic field produced at the centre by the same current will be:
four times its first value
a half of its first value
unaltered
a quarter of its first value
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1 solution
Imagine that the magnetic field produced by single turn of coil be X. Now this is inversly proportional to the square of the radius of the coil (Use biot savarts law).Now in the second case the radius is exactly halved so it is (1/2) times now. The resultant field will be (1/1/2)^2*X=4X