A current carrying straight wire is kept along the axis of a circular loop carrying a current. The straight wire 

A coil of $100$ turns and area $2\times {10}^{-2}{m}^2,$ pivoted about a vertical diameter in a uniform magnetic field carries a current of $5A.$ When the coil is held with its plans north-south direction, it experiences a torque $0.3 Nm.$ When the plane is east-west direction the torque is $0.4 Nm.$ The value of the magnetic induction is (neglect earth's magnetic field)

The resultant force on the current loop $PQRS$ of Fig.$8.130,$ due to the long current carrying conductor will be 

Three long straight wires $A,B$ and $C$ are carrying currents as shown in Fig.$8.131.$Then the resultant force on $B$ is directed 

A conducting loop carrying a current $I$ is placed in a uniform magnetic field pointing into the plane of the paper as shown in Fig. The loop will have a tendency to

$A$ and $B$ are two concentric coils of centre $O$ and carry currents $I_1$ and $I_2$ are shown in Fig.$8.133.$ If the ratio of their radii $1:2$ and the ratio of the flux densities at O due to $A$ and $B$ is $1:3,$ then value of $\frac{I_1}{I_2}$ is-