Question

A solenoid has 500 turns of wire in its 40 cm length. If the current in the wire is 1 A, then magnetic field at the centre of the solenoid is

• A.
  Zero
• B.
  $1250{\mu }_{0}T$
• C.
  $\pi T$
• D.
  ${\mu }_{0}T$

Answer 1

The correct option is B

$1250{\mu }_{0}T$
Given: N = 500, l = 40 cm

$\Rightarrow$ No. of turns per unit length,$n=\frac{N}{l}=\frac{500}{0.40}=1250$

Magnetic field at the centre of the solenoid, $B={\mu }_{0}nI={\mu }_0\times 1250\times 1[Currecntinthewire,i=1A]=1250{\mu }_{0}T$

Hence, the correct answer is option (b).