For the magnetic field to be maximum due to a small element of current-carrying conductor at a point, the angle between the element and the line joining the element to the given point must be:

1. 0°                           
2. 90°
3. 180°                        
4. 45°

An electron and a proton enter a magnetic field perpendicularly. Both have the same kinetic energy. Which of the following is true:

1. Trajectory of electron is less curved

2. Trajectory of proton is less curved

3. Both trajectories are equally curved

4. Both move on a straight-line path

A proton, a deuteron, and an $\alpha -$ particle having the same kinetic energy are moving in circular trajectories in a constant magnetic field. If $r_p,r_d$ and $r_{\alpha }$ denote respectively the radii of the trajectories of these particles, then:

1. $r_{\alpha }=r_p<r_d$                             

2.  $r_a>r_d>r_p$ 

3. $r_{\alpha }=r_d>r_p$                             

4.  $r_p=r_d=r_{\alpha }$ 

An electron and a proton with equal momentum enter perpendicularly into a uniform magnetic field, then :

1. The path of proton shall be more curved than that of electron

2. The path of proton shall be less curved than that of electron

3. Both are equally curved

4. Path of both will be a straight line

One proton beam enters a magnetic field of ${10}^{-4}T$ normally, Specific charge = ${10}^{11}C/kg.$ velocity = ${10}^{7}m/s.$ What is the radius of the circle described by it:

1. $0.1m$                               

2. $1m$

3. $10m$                               

4. None of these

The maximum kinetic energy of the positive ion of charge q and mass m in the cyclotron of radius \(r_o\) in which applied magnetic field is B, is:

1. $\frac{q^{2}B{r}_0}{2m}$                        

2. $\frac{q{B}^2{r}_0}{2m}$

3. $\frac{q^2{B}^2{r}_0^2}{2m}$                        

4. $\frac{qB{r}_0}{2m^2}$

An electron of mass m and charge q is traveling with a speed v along a circular path of radius r at right angles to a uniform of the magnetic field B. If the speed of the electron is doubled and the magnetic field is halved, then resulting path would have a radius of:

1. $\frac{r}{4}$                           

2. $\frac{r}{2}$ 

3. $2r$                           

4. $4r$

Cyclotron cannot be used to accelerate

1. Electrons                       

2. Neutrons

3. Positive ions                   

4. Both (1) and (2)

Two particles A and B of masses $m_A$ and $m_B$ respectively and having the same type of charge are moving in a plane. A uniform magnetic field exists perpendicular to this plane. The speeds of the particles are $v_A$ and $v_B$ respectively, and the trajectories are as shown in the figure. Then

1. $m_A{v}_A<m_B{v}_B$                              

2. $m_A{v}_A>m_B{v}_B$

3. $m_A<m_B and v_A<v_B$                  

4. $m_A=m_B and v_A=v_B$

Magnetic field due to a ring having n turns at a distance x on its axis is proportional to (if r = radius of ring) :

1.  $\frac{\mathrm{r}}{({\mathrm{x}}^2+{\mathrm{r}}^2)}$                                     

2.  $\frac{{\mathrm{r}}^2}{({\mathrm{x}}^2+{\mathrm{r}}^2{)}^{3/2}}$

3.  $\frac{{\mathrm{nr}}^2}{({\mathrm{x}}^2+{\mathrm{r}}^2{)}^{3/2}}$                                 

4.  $\frac{{\mathrm{n}}^2{\mathrm{r}}^2}{({\mathrm{x}}^2+{\mathrm{r}}^2{)}^{3/2^{}}}$