Question

One metre length of wire carries a constant current. The wire is bent to form a circular loop. The magnetic field at the centre of this loop is B. The same is now bent to form a circular loop of smaller radius to have four turns in the loop. The magnetic field at the centre of this new loop is

• A. 4 B
• B. 16 B
• C.
• D. $B / 4$

Answer 1

Answer: (B)

16 B

Answer 2

$B ^ { \prime } = n ^ { 2 } B \Rightarrow B ^ { \prime } = ( 4 ) ^ { 2 } B = B ^ { \prime } = 16 B$