A long wire AB is placed on a table. Another wire PQ of mass 1.0 g and length 50 cm is set to slide on two rails PS and QR. A current of 50A is passed through the wires. At what distance above AB, will the wire PQ be in equilibrium

                     

(1) 25 mm                           

(2) 50 mm

(3) 70 mm                           

(4) 100 mm

A particle with charge q, moving with a momentum p, enters a uniform magnetic field normally. The magnetic field has magnitude B and is confined to a region of width d, where $d<\frac{p}{Bq}$. The particle is deflected by an angle $\theta$ in crossing the field, then :

(a) $\sin \theta =\frac{Bqd}{p}$                              (b) $\sin \theta =\frac{p}{Bqd}$

(c) $\sin \theta =\frac{Bp}{qd}$                                (d) $\sin \theta =\frac{pd}{Bq}$

The same current i = 2A is flowing in a wireframe as shown in the figure. The frame is a combination of two equilateral triangles ACD and CDE of side 1m. It is placed in uniform magnetic field B = 4T acting perpendicular to the plane of the frame. The magnitude of the magnetic force acting on the frame is:

1. 24 N                                         2. Zero

3. 16 N                                         4. 8 N

In the given figure, net magnetic field at O will be 

1. $\frac{2{\mu }_{0}i}{3\mathrm{\pi a}}\sqrt{4-{\pi }^2}$                                 
2. $\frac{{\mu }_{0}i}{3\mathrm{\pi a}}\sqrt{4+{\pi }^2}$

3. $\frac{2{\mu }_{0}i}{3\mathrm{\pi a}}\sqrt{4+{\pi }^2}$                               
4. $\frac{2{\mu }_{0}i}{3\mathrm{\pi a}}\sqrt{\left(4-{\mathrm{\pi }}^2\right)}$

In the following figure, a wire bent in the form of a regular polygon of n sides is inscribed in a circle of radius a. The net magnetic field at centre will be $\left(\theta =\frac{\pi }{n}\right)$

(a) $\frac{{\mu }_{o}i}{2\mathrm{\pi a}}\tan \frac{\mathrm{\pi }}{n}$                                                (b) $\frac{{\mu }_{0}ni}{2\mathrm{\pi a}}\tan \frac{\mathrm{\pi }}{n}$

(c)$\frac{2}{\mathrm{\pi }}\frac{ni}{a}{\mu }_0\tan \frac{\mathrm{\pi }}{n}$                                             (d) $\frac{ni}{2a}{\mu }_0\tan \frac{\mathrm{\pi }}{n}$

An elastic circular wire of length L carries a current I. It is placed in a uniform magnetic field $\overrightarrow{B}$ (out of paper) such that its plane is perpendicular to the direction of $\overrightarrow{B}$ . The wire will experience

(1) No force                           

(2) A stretching force

(3) A compressive force           

(4) A torque

Wires 1 and 2 carrying currents $i_1$ and $i_2$ respectively are inclined at an angle $\theta$ to each other. What is the force on a small element dl of wire 2 at a distance of r from wire 1 (as shown in figure) due to the magnetic field of wire 1

(a) $\frac{{\mu }_0}{2\mathrm{\pi r}}{i}_1{i}_{2}dl \tan \theta$                              (b) $\frac{{\mu }_0}{2\mathrm{\pi r}}{i}_1{i}_{2}dl \sin \theta$

(c) $\frac{{\mu }_0}{2\mathrm{\pi r}}{i}_1{i}_{2}dl \cos \theta$                               (d) $\frac{{\mu }_0}{4\mathrm{\pi r}}{i}_1{i}_{2}dl \sin \theta$

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

(1) Contract                                       

(2) Expand 

(3) Move towards +ve x -axis               

(4) Move towards -ve x -axis

A current-carrying loop is placed in a uniform magnetic field in four different orientations, I, II, III & IV. The decreasing order of potential energy is :

(1) I > III > II > IV                               

(2) I > II >III > IV

(3) I > IV > II > III                               

(4) III > IV > I > II

Two insulated rings, one of a slightly smaller diameter than the other, are suspended along their common diameter as shown. Initially, the planes of the rings are mutually perpendicular. What happens when a steady current is set up in each of them?