Question

A circular current carrying coil has a radius R. The distance from the centre of the coil on the axis where the magnetic induction will be $\frac { 1 } { 8 } t h$ to its value at the centre of the coil, is

• A. $\frac { \mathrm { R } } { \sqrt { 3 } }$
• B.
• C. $2 \sqrt { 3 } R$
• D. $\frac { 2 } { \sqrt { 3 } } \mathrm { R }$

Answer 1

Answer: (B)

Answer 2

According to the question, at centre of coil

$B = B _ { H } \Rightarrow \frac { \mu _ { 0 } } { 4 \pi } \cdot \frac { 2 \pi i } { r } = B _ { H }$

⇒ $10 ^ { - 7 } \times \frac { 2 \pi i } { \left( 5 \times 1 ^ { - 2 } \right) } = 7 \times 10 ^ { - 5 }$

⇒ $i = 5.6$ amp.