$A$ thin circular wire carrying current $I$ has magnetic moment $M$. The shape of the wire is changed to a square and it carries the same current. It will have magnetic moment $M_1$. The ratio $M$ to $M_1$ 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 current connection indicated. The magnetic field at the centre of the square is zero in cases:

$A$ particle of mass $m$ and charge $Q$ moving with a speed $v$ in a circular path of radius $R$ has a magnetic moment $\mu$. If the mass of the particle is doubled and it maintains the same speed while revolving in the same circular path, then the magnetic moment will be

Two circular concentric loops of radii $r_1 = 20\,cm$ and $r_2 = 30\,cm$ are placed in the $X, Y-$ plane as shown in the figure. $A$ current $I = 7\,A$ is flowing through them in opposite directions. The magnetic moment of this loop system is

Due to the flow of current in a circular loop of radius $R$,the magnetic induction produced at the centre of the loop is $B$. The magnetic moment of the loop is (where ${\mu _0}$ is the permeability constant).

$A$ closely wound solenoid of $1000$ turns and area of cross-section $2 \times 10^{-4} \ m^2$ carrying a current of $5.0 \ A$. The magnetic moment is . . . . . . $A \ m^2$.