MCQ
A hollow cylinder having infinite length and carrying uniform current per unit length $\lambda$ along the circumference as shown. Magnetic field inside the cylinder is
  • A
    $\frac{{{\mu _0}\lambda }}{2}$
  • $\mu_0 \lambda$
  • C
    $2\mu_0 \lambda$
  • D
    none

Answer

Correct option: B.
$\mu_0 \lambda$
b
Hint: Apply Biot Savart's law

Step $1:$

Given a hollow cylinder that has infinite length and carrying current per unit length $\lambda$ along the circumference.

Here $\lambda=\frac{ I }{2 \pi r }$ ie.., current flowing per unit length.

$I =\lambda 2 \pi r \text { (1) }$

The magnetic field inside the cylinder is given by

$B =\frac{\mu_0}{4 \pi} \times \frac{2 I }{ r } \text { (2) }$

Step $2:$

Substitute the value of I from eq: $(1)$ in $(2)$ we get

$B =\frac{2 \mu_0}{4 \pi} \times \frac{\lambda 2 \pi r }{ r }$

$\Rightarrow B =\mu_0 \lambda$

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