Two long and parallel straight wires $A$ and $B$ carrying currents of $10 \ A$ and $4 \ A$ in the same direction are separated by a distance of $2 \ cm$. Estimate the force on a $4 \ cm$ section of wire $A$. ( $\mu_0 = 4 \pi \times 10^{-7} \ SI$ ).

$A$ square of side $2.0\,m$ is placed in a uniform magnetic field $B = 2.0\,T$ in a direction perpendicular to the plane of the square inwards. Equal current,$i = 3.0\,A$ is flowing in the direction shown in the figure. Find the magnitude of the magnetic force on the loop.

What is the magnitude of magnetic force per unit length (in $N \;m^{-1}$) on a wire carrying a current of $8 \;A$ and making an angle of $30^{\circ}$ with the direction of a uniform magnetic field of $0.15 \;T$?

When current passing through two parallel wires flows in the same direction,the force between them is $......$,while when current passes in opposite directions through the same wires,the force between them is $......$ (attraction,repulsion).

$A$ massless square loop of wire of resistance $R$ supporting a mass $M$ hangs vertically with one of its sides in a uniform magnetic field $B$ directed outwards in the shaded region. $A$ d.c. voltage $V$ is applied to the loop. For what value of $V$ will the magnetic force exactly balance the weight of the supporting mass $M$? (side of loop $= L, g =$ acceleration due to gravity)

In the given figure,$X$ and $Y$ are two long straight parallel conductors each carrying a current of $2\,\text{A}$. The force on each conductor is $F$ newtons. When the current in each is changed to $1\,\text{A}$ and reversed in direction,the force on each is now