$A$ square loop of side '$a$' carrying a current '$I$' is suspended from an insulating hanger of a spring balance as shown in the figure. The transverse magnetic field '$B$' directed into the paper occurs only at the bottom side of the loop. When the direction of current in the loop is reversed, the change in the reading of the spring balance is:

The force acting on a current-carrying wire joining two fixed points $A$ and $B$ in a uniform magnetic field is:

The figure shows a cross-section of an infinite metal sheet carrying an electric current along its surface. The current per unit length is $J$. $A$ current-carrying square loop is placed nearby the metal sheet such that the plane of the square is perpendicular to the plane of the sheet. Then:

$A$ circular current loop of radius $a$ is placed in a radial magnetic field $B$ as shown in the figure. The net force acting on the loop is

$A$ current loop $ABCD$ is held fixed on the plane of the paper as shown in the figure. The arcs $BC$ (radius $= b$) and $DA$ (radius $= a$) of the loop are joined by two straight wires $AB$ and $CD$. $A$ steady current $I$ is flowing in the loop. The angle made by $AB$ and $CD$ at the origin $O$ is $30^o$. Another straight thin wire with a steady current $I_1$ flowing out of the plane of the paper is kept at the origin. Due to the presence of the current $I_1$ at the origin:

Through two parallel wires $A$ and $B$,$10 \, A$ and $2 \, A$ of currents are passed respectively in opposite directions. If the wire $A$ is infinitely long and the length of the wire $B$ is $2 \, m$,the force on the conductor $B$,which is situated at a $10 \, cm$ distance from $A$,will be: