The magnetic field due to a long straight wire carrying a current $I$ is proportional to:

$A$ circular coil of wire consisting of $100$ turns,each of radius $8.0 \; cm$,carries a current of $0.40 \; A$. What is the magnitude of the magnetic field $B$ at the centre of the coil?

The current passing through a conducting loop in the form of an equilateral triangle of side $4\sqrt{3} \text{ cm}$ is $2 \text{ A}$. The magnetic field at its centroid is $\alpha \times 10^{-5} \text{ T}$. The value of $\alpha$ is . . . . . . . (Given: $\mu_0 = 4\pi \times 10^{-7} \text{ SI units}$)

State and explain the Biot-Savart law for the magnetic field produced by a current element. Give the direction of the magnetic field and define its unit.

The magnitude of the magnetic field at the centre of an equilateral triangular loop of side $1\,m$ which is carrying a current of $10\,A$ is:......$\mu T$ [Take $\mu _0 = 4\pi \times 10^{-7}\,NA^{-2}$]

The magnetic induction at a point $P$ which is distant $4 \, cm$ from a long current-carrying wire is $10^{-8} \, T$. The magnetic field induction at a distance $12 \, cm$ from the same current would be: