A Rowland ring of mean radius $15\; cm\;3500$ turns of wire wound on a ferromagnetic core of relative permeability $800.$ What is the magnetic field $B$ (in $T$) in the core for a magnetizing current of $1.2\; A?$

Find magnetic field at centre $P$ if length of side of square loop is $20\, cm$

Two concentric coils each of radius equal to $2\pi \,{\rm{ }}cm$ are placed at right angles to each other. $3$ $ampere$ and $4$ $ampere$ are the currents flowing in each coil respectively. The magnetic induction in $Weber/{m^2}$ at the centre of the coils will be $({\mu _0} = 4\pi \times {10^{ - 7}}\,Wb/A.m)$

The following statement is false for Helmholtz coils

A current of $i$ ampere is flowing through each of the bent wires as shown the magnitude and direction of magnetic field at $O$ is 

Two circular loops having same radius $[ R =10\, cm ]$ and same current $\frac{7}{2} A$ are placed along same axis as shown. If distance between their centre is $10\, cm$, find net magnetic field at of point $P.$