Question

A circular loop of radius 0.3 cm lies parallel to a much bigger circular loop of radius 20 cm. The centre of the smaller loop is on the axis of the bigger loop. The distance between their centres is 15 cm. If a current of 2.0 A flows through the bigger loop, then the flux linked with smaller loop is

• A. 9.1 $\times 10^{-11} Wb$
• B. $6 \times 1^{-11} Wb$
• C. 3.3 $\times 10^{-11}Wb$
• D. $6.6 \times 10^(-9)Wb$

Answer 1

Answer: (A)

9.1 $\times 10^{-11} Wb$

Answer 2

Magnetic field at the centre of smaller loop
$\, \, \, \, \, \, \, \, \, \, \, \, B =\frac{\mu _0 iR_2^2}{2(R_2^2+x^2)^{3/2}}$
Area of smaller loop S = $\pi R_1^2$
$\therefore \, \,$Flux through smaller loop $\phi$ = BS
Substituting the values we get, $\phi = 9.1 \times 10^{-11}Wb$