Magnetism and Matter — Physics STD 12 Science — Question

Two identical short bar magnets, each having magnetic moment of 10 Am², are arranged such that their axial lines are perpendicular to each other and their centres be along the same straight line in a horizontal plane. If the distance between their centres is 0.2 m, the resultant magnetic induction at a point  midway between them  is ( 

(a)  Tesla

(b)  Tesla

(c)  Tesla

(d)  Tesla

An electric bulb marked 40 W and 200 V, is used in a circuit of supply voltage 100 V. Now its power is

(a) 100W

(b) 40W

(c) 20W

(d) 10W

A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is 2/3. Their equivalent focal length is 30 cm. What are their individual focal lengths

(a) – 75, 50

(b) – 10, 15

(c) 75, 50

(d) – 15, 10

The correct relation is (Where  Horizontal component of earth's magnetic field;  = Vertical component of earth's magnetic field and B  = Total intensity of earth's magnetic field)

(a) B =

(b)

(c) |B| =

(d)

Two particles A₁ sand A₂ of masses m₁, m₂ (m₁ > m₂) have the same de-Broglie wavelength. Then:

An X-ray tube is operated at 50 kV. The minimum wavelength produced is

(a) 0.5 Å

(b) 0.75 Å

(c) 0.25 Å

(d) 1 Å

In a streamline flow:

1. The speed of a particle always remains same.
2. The velocity of a particle always remains same.
3. The kinetic energies of all the particles arriving at a given point are the same.
4. The momenta of all the particles arriving at a given point are the same.

The electric field inside a conductor.

The mass number of He is 4 and that for sulphur is 32. The radius of sulphur nucleus is larger than that of helium, by times

(a)

(b) 4

(c) 2

(d) 8