The figure shows a particle of charge q and mass m moving with velocity v along the x-axis enters a region of the uniform magnetic field. The minimum value of v so that the charge q is deflected by an angle $30°$ is

                                       

1.  $\frac{2\mathrm{qB}\left(\mathrm{b} - \mathrm{a}\right)}{\mathrm{m}}$

2.  $\frac{\mathrm{qB}\left(\mathrm{b} + \mathrm{a}\right)}{2\mathrm{m}}$

3.  $\frac{\mathrm{qB}\left(\mathrm{b} - \mathrm{a}\right)}{\mathrm{m}}$

4.  $\frac{\mathrm{qBb}}{2\mathrm{m}}$

An electron is traveling along the x-direction. It encounters a magnetic field in the y-direction. Its subsequent motion will be:

1.  Straight-line along the x-direction

2.  A circle in the xz-plane

3.  A circle in the yz-plane

4.  A circle in the xy-plane

A closed-loop (of any shape) carrying current lies in the x-y plane. What happens when a uniform magnetic field B is present in the region such that the loop experiences zero force?

A galvanometer of resistance 240 Ω allows only 4% of the main current after connecting a shunt resistance. What is the value of shunt resistance?

1.  10 $\mathrm{\Omega }$

2.  20 $\mathrm{\Omega }$

3.  8 $\mathrm{\Omega }$

4.  5 $\mathrm{\Omega }$

The dots in the figure depict a magnetic field that is perpendicular to the plane of the paper and emanates from it. The trajectory of a particle in the plane of the paper is depicted by the curve ABC. What exactly is the particle?

A long solenoid has 800 turns per meter length of the solenoid. A current of 1.6 A flows through it. The magnetic induction at the end of the solenoid on its axis is:

1.  $16\times {10}^{-4} \mathrm{T}$

2.  $8\times {10}^{-4} \mathrm{T}$

3.  $32\times {10}^{-4} \mathrm{T}$

4.  $4\times {10}^{-4} \mathrm{T}$

The unit of reduction factor of the tangent galvanometer is 

(1) Ampere

(2) Gauss

(3) Radian

(4) None of these

In order to pass 10% of the main current through a moving coil galvanometer of 99 ohms, the resistance of the required shunt is :

(1) 9.9 Ω

(2) 10 Ω

(3) 11 Ω

(4) 9 Ω

When a 12 Ω resistor is connected in parallel with a moving coil galvanometer, its deflection reduces from 50 divisions to 10 divisions. What will be the resistance of the galvanometer?

1. 24 Ω

2. 36 Ω

3. 48 Ω

4. 60 Ω

A voltmeter has a resistance of G ohms and range V volts. The value of resistance used in series to convert it into a voltmeter of range nV volts is :

(1) nG

(2) $(n-1)G$

(3) $\frac{G}{n}$ 

(4) $\frac{G}{(n-1)}$