Question

A tightly wound $100$ turns coil of radius $10 cm$ carries a current of $7 A$. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as $4\pi×10^{-7}$ SI units):

• A. $44mT$
• B. $4.4T$
• C. $4.4mT$
• D. $44 T$

Answer 1

Answer: (C)

$4.4mT$

Answer 2

The magnetic field at the centre of a circular coil is given by:

$B = \frac{\mu_0 N I}{2R}$,

where $N$ is the number of turns,
$I$ is the current,
$R$ is the radius, and
$\mu_0$ is the permeability of free space.
Substituting the values:

$B = \frac{(4\pi \times 10^{-7}) \times 100 \times 7}{2 \times 0.1} = 4.4 \, mT$.