The magnetic force between the wires as shown in the figure is:

Two long straight parallel wires,carrying (adjustable) current $I_1$ 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 thin long parallel wires, $W_1$ and $W_2$ separated by distance '$a$',carry currents $i$ and $3i$ respectively in the same direction. The magnitude of the force per unit length exerted by wire $W_1$ on wire $W_2$ is

The figure shows a conducting loop $ABCDA$ placed in a uniform magnetic field perpendicular to its plane. The part $ABC$ is the $(3/4)^{th}$ portion of the square of side length $l$. The part $ADC$ is a circular arc of radius $R$. The points $A$ and $C$ are connected to a battery which supplies a current $I$ to the circuit. The magnetic force on the loop due to the field $B$ is

The horizontal component of the Earth's magnetic field at a certain place is $3 \times 10^{-5} \, T$ and the direction of the field is from geographic south to geographic north. $A$ very long straight conductor is carrying a steady current of $1 \, A$. Calculate the force per unit length on it if the direction of the current is from east to west (in $N/m$).

In an experiment,setup $A$ consists of two parallel wires which carry currents in opposite directions as shown in the figure. $A$ second setup $B$ is identical to setup $A$,except that there is a metal plate between the wires. Let $F_A$ and $F_B$ be the magnitude of the force between the two wires in setup $A$ and setup $B$,respectively.