A rectangular loop carrying a current i is situated near a long straight wire such that the wire is parallel to the one of the sides of the loop and is in the plane of the loop. If a steady current I is established in wire as shown in figure, the loop will

                                          

(1) Rotate about an axis parallel to the wire

(2) Move away from the wire or towards right

(3) Move towards the wire

(4) Remain stationary

Two thin long parallel wires separated by a distance b are carrying a current i amp each. The magnitude of the force per unit length exerted by one wire on the other is

(1) $\frac{{\mu }_0{i}^2}{b^2}$                                 

(2) $\frac{{\mu }_0{i}^2}{2\mathrm{\pi b}}$ 

(3) $\frac{{\mu }_{0}i}{2\mathrm{\pi b}}$                                  

(4) $\frac{{\mu }_{0}i}{2{\mathrm{\pi b}}^2}$ 

To make the field radial in a moving coil galvanometer :

(1) The number of turns in the coil is increased

(2) Magnet is taken in the form of horse-shoe

(3) Poles are cylindrically cut

(4) The coil is wounded on the aluminum frame

In a moving coil galvanometer, the deflection of the coil $\theta$ is related to the electrical current i by the relation

(1) $i\propto \tan \theta$                 

(2) $i\propto \theta$ 

(3) $i\propto {\theta }^2$                    

(4) $i\propto \sqrt{\theta }$ 

A moving coil galvanometer has N number of turns in a coil of effective area A, it carries a current I. The magnetic field B is radial. The torque acting on the coil is 

(1) $N{A}^2{B}^{2}I$                          

(2) $NAB{I}^2$

(3) $N^{2}ABI$                            

(4) $NABI$

If a particle of charge ${10}^{-12}$ coulomb moving along the $\hat{x} -$ direction with a velocity ${10}^5$ m/s experiences a force of ${10}_{}^{-10}$ newton in $\hat{y}$- direction due to magnetic field, then the minimum magnetic field is 

(1)  $6.25\times {10}^3$ tesla in $\hat{z}$- direction

(2)  ${10}^{-15}$  tesla in $\hat{z}$- direction

(3)  $6.25\times {10}^{-3}$ tesla in $\hat{z}$- direction

(4)  ${10}^{-3}$ tesla in $\hat{z}$- direction 

A small coil of N turns has an effective area A and carries a current I. It is suspended in a horizontal magnetic field $\stackrel{.}{B}$ such that its plane is perpendicular to $\stackrel{.}{B}$. The work done in rotating it by $180°$ about the vertical axis is 

(a) $NAIB$                               (b) $2NAIB$ 

(c) $2\mathrm{\pi NAIB}$                          (d) $4\mathrm{\pi }NAIB$

An electron moves with a constant speed v along a circle of radius r. Its magnetic moment will be (e is the electron's charge)

(1) evr                       

(2) $\frac{1}{2}$evr 

(3) ${\mathrm{\pi r}}^2$ev                    

(4) 2$\mathrm{\pi }$rev 

Four wires each of length 2.0 metres are bent into four loops P, Q, R and S and then suspended into uniform magnetic field. Same current is passed in each loop. Which statement is correct?

(1) Couple on loop P will be the highest

(2) Couple on loop Q will be the highest

(3) Couple on loop R will be the highest

(4) Couple on loop S will be the highest

A circular current carrying coil has a radius R. The distance from the centre of the coil on the axis where the magnetic induction will be $\frac{1}{8}\mathrm{th}$ to its value at the centre of the coil, is

(1) $\frac{\mathrm{R}}{\sqrt{3}}$                       

(2)  $\mathrm{R}\sqrt{3}$

(3) $2\sqrt{3}\mathrm{R}$                     

(4) $\frac{2}{\sqrt{3}}\mathrm{R}$