$A$ conducting wire bent in the form of a parabola $y^2 = 2x$ carries a current $i = 2 \, A$ as shown in the figure. This wire is placed in a uniform magnetic field $\vec{B} = -4\,\hat{k} \, T$. The magnetic force on the wire is (in newton):

$A$ current of $1 \ A$ is flowing along the positive $x$-axis through a straight wire of length $0.5 \ m$ placed in a region of a magnetic field given by $\vec{B} = (2\hat{i} + 4\hat{j}) \ T$. The magnitude and the direction of the force experienced by the wire are,respectively:

$A$ current-carrying rectangular loop $PQRS$ is made of uniform wire. The lengths are $PR = QS = 5\,cm$ and $PQ = RS = 100\,cm$. If the 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,$f_{PQ}^{I} : f_{PQ}^{2I}$,is:

Assertion $(A):$ $A$ wire is bent into an irregular shape with the points $P$ and $Q$ fixed. If a current $I$ is passed through the wire,then the area enclosed by the irregular portion of the wire increases.
Reason $(R):$ Wires carrying currents in opposite directions repel each other.

$A$ horizontal semi-circular wire of radius $r$ is connected to a battery through two similar springs $X$ and $Y$. The battery sends a current $I$ through the wire. $A$ uniform magnetic field $B$ is applied perpendicular to the plane of the wire,as shown in the figure. What is the force acting on each spring?

Three long straight wires $A$,$B$,and $C$ are carrying currents as shown in the figure. Then the resultant force on $B$ is directed .....