The magnetic induction at any point due to a long straight wire carrying a current is

$A$ coil of $n$ number of turns is wound tightly in the form of a spiral with inner and outer radii $a$ and $b$ respectively. When a current of strength $I$ is passed through the coil,the magnetic field at its centre is

Two thick wires and two thin wires,all of the same material and same length,form a square in three different ways $P, Q,$ and $R$ as shown in the figure. With the correct connections shown,the magnetic field due to the current flow at the centre of the loop will be zero in the case of:

$A$ uniform circular wire loop is connected to the terminals of a battery. The magnetic field induction at the centre due to $ABC$ portion of the wire will be (length of $ABC = l_1$, length of $ADC = l_2$):

$A$ horizontal overhead powerline is at a height of $4\ m$ from the ground and carries a current of $100\ A$ from east to west. The magnetic field directly below it on the ground is: (Given: $\mu_0 = 4\pi \times 10^{-7} \, T \cdot m/A$)

Find the magnetic field at the centre $P$ of a square loop of side length $20 \, cm$ carrying a current of $3 \, A$.