A current carrying rectangular loop PQRS is made of uniform wire. The length PR=QS=5 cm and PQ=RS=100 cm. If ammeter current reading changes from I to 2I, the ratio of magnetic forces per unit length on the wire PQ due to wire RS in the two cases respectively ${\mathrm{f}}_{\mathrm{PQ}}^{\mathrm{I}} : {\mathrm{f}}_{\mathrm{PQ}}^{2\mathrm{I}} \mathrm{is}:$

 

Two parallel very long straight wires carrying current of $5 \mathrm{A}$ each are kept at a separation of $1 \mathrm{m}.$ If the currents are in the same direction, the force per unit length between them is _____ $\mathrm{N} {\mathrm{m}}^{-1}. \left({\mu }_0=4\pi \times {10}^{-7} \mathrm{SI}\right)$

Two long straight parallel wires, carrying (adjustable) currents $I_1$ and $I_2$ , are kept at a distance $d$ apart. If the force $F$ between the two wires is taken as 'positive' when the wires repel each other and 'negative' when the wires attract each other, the graph showing the dependence of $F$, on the product $I_1{I}_2$ , would be:

Two long conductors, separated by a distance $d$ carry currents $I_1$  and $I_2$ in the same direction. They exert a force $F$ on each other. Now the current in one of them is increased to two times and its direction is reversed. The distance is also increased to $3d$. The new value of force between them is

Write an expression for force per unit length between two long current-carrying wires, kept parallel to each other, in a vacuum and hence define an ampere, the SI unit of current.

Consider two straight parallel conductors $A$ and $B$ separated by a distance $x$ and carrying individual currents $i_A \mathrm{a}\mathrm{n}\mathrm{d}\mathrm{ }{i}_B$ respectively. If the two conductors attract each other, it indicates that

 A long horizontal wire P carries a current of $50 A$. It is rigidly fixed. Another wire Q is placed directly above and parallel to P as shown in Figure 1 below. The weight per unit length of the wire Q is $0.025 \mathrm{N} {\mathrm{m}}^{-1}$ and it carries a current of $25 A$. Find the distance r of the wire Q from the wire P so that the wire Q remains at rest.

Calculate force per unit length acting on the wire B due to the current flowing in the wire A. (See figure 2 below):

A rigid square loop of side $\mathrm{‘}\mathrm{a}’$ and carrying current ${\mathrm{I}}_2$ is lying on a horizontal surface near a long current ${\mathrm{I}}_1$ carrying wire in the same plane as shown in figure. The net force on the loop due to the wire will be:

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