A straight conductor carrying current I splits into two parts as shown in the figure. The radius of the circular loop is R. The total magnetic field at the centre P of the loop is,

(1)  zero

(2) $\frac{3{\mu }_{0}i}{32R}, inward$

(3) $\frac{3{\mu }_{0}i}{32R}, outward$

(4) $\frac{{\mu }_{0}i}{2R}, inward$

In an ammeter 0.2% of main current passes through the galvanometer. If resistance of galvanometer is G, the resistance of ammeter will be:

1. $\frac{1}{499}G$

2. $\frac{499}{500}G$

3. $\frac{1}{500}G$

4. $\frac{500}{499}G$

A beam of electrons passes un-deflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move:

1. in an elliptical orbit

2. in a circular orbit

3. along a parabolic path

4. along a straight line

When a charged particle moving with velocity $\overline{v}$ is subjected to a magnetic field of induction $\overline{B}$, the force on it is non-zero. This implies that:

1. angle between $\overline{v}$ and $\overline{B}$ is necessarily 90^o.

2. angle $\overline{v}$ and $\overline{B}$ between can have any value other than 90^o.

3. angle between $\overline{v}$ and $\overline{B}$ have any value other than zero and 180^o.

4. angle between $\overline{v}$ and $\overline{B}$ is either zero or 180^o.

A circuit contains an ammeter, a battery of 30 V, and a resistance 40.8 $\Omega$all connected in series. If the ammeter has the coil of resistance 480 $\Omega$and a shunt of 20 $\Omega$, then reading in the ammeter will be:

1. 0.5 A

2. 0.02 A

3. 2 A

4. 1 A

${\mathrm{O}}^{++}, {\mathrm{C}}^{+}, {\mathrm{He}}^{++}$ and ${\mathrm{H}}^{+}$ ions are projected on the photographic plate with the same velocity in a mass spectrograph. Which one will strike the farthest?

1. ${\mathrm{O}}^{++}$                  2. ${\mathrm{C}}^{+}$
3. ${\mathrm{He}}^{++}$                4. ${\mathrm{H}}_2^{+}$

A beam of cathode rays is subjected to crossed Electric (E) and magnetic fields(B). The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by:

1. $\frac{B^2}{2V{E}^2}$                                             2. $\frac{2V{B}^2}{E^2}$

3. $\frac{2V{E}^2}{B^2}$                                            4. $\frac{E^2}{2V{B}^2}$

(where V is the potential difference between cathode and anode)