Two parallel wires of length $9\, m$ each are separated by a distance $0.15\, m$. If they carry equal currents in the same direction and exerts a total force of $30 \times 10^{-7} \,N$ on each other, then the value of current must be........$amp$

Suppose an isolated north pole is kept at the centre of a circular loop carrying a electric current $i$. The magnetic field due to the north pole at a point on the periphery of the wire is $B$. The radius of the loop is $a$. The force on the wire is

Three long, straight and parallel wires carrying currents are arranged as shown in the figure. The wire $C$ which carries a current of $5.0\, amp$ is so placed that it experiences no force. The distance of wire $C$ from wire $D$ is then

An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current $'I'$ along the same direction as shown in figure. Magnitude of force per unit length on the middle wire $'B'$ is given by 

A long straight wire carrying current of $25$ $\mathrm{A}$ rests on a table as shown in figure. Another wire $\mathrm{PQ}$ of length $1$ $\mathrm{m}$, mass $2.5$ $\mathrm{g}$ carries the same current but in the opposite direction. The wire $\mathrm{PQ}$ is free to slide up and down. To what height will $\mathrm{PQ}$ rise ? 

Three long, straight parallel wires carrying current, are arranged as shown in figure. The force experienced by a $25\, cm$ length of wire $C$ is