Two long conductors, separated by a distance $d$ carry current $I_1$ 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 directions is reversed. The distance is also increased to $3d$. The new value of the force between them is

A stream of electrons is projected horizontally to the right. A straight conductor carrying a current is supported parallel to electron stream and above it. If the current in the conductor is from left to right then what will be the effect on electron stream

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........$amp$

A circular loop has a radius of $5\, cm$ and it is carrying a current of $0.1\, amp$. Its magnetic moment is

Three long, straight and parallel wires carrying currents are arranged as shown in figure. The force experienced by $10\, cm$ length of wire $Q$ is

A non conducting ring (of mass $m,$ radius $r,$ having charge $Q$) is placed on a rough horizontal surface (in a region with transverse magnetic field). The field is increasing with time at the rate $R$ and coefficient of friction between the surface and the ring is $\mu .$ For ring to remain in equilibrium $\mu$ should be greater than