Moving Charges and Magnetism — Physics STD 12 Science — Question

The electromagnetic wave of highest frequency is :

A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4D, the power of a cutlens will be:

1. 2D
2. 3D
3. 4D
4. 5D.

Diameter of a plano–convex lens is 6 cm and thickness at the centre is 3 mm. If the speed of light in the material of the lens is 2 × 10⁸ m/sec, the focal length of the lens is

(a) 15 cm

(b) 20 cm

(c) 30 cm

(d) 10 cm

To get line spectrum, the substances are excited in their:

In a transformer, the coefficient of mutual inductance between the primary and the secondary coil is 0.2 henry. When the current changes by 5 ampere/second in the primary, the induced e.m.f. in the secondary will be

(a)  5 V

(b) 1 V

(c)  25 V

(d) 10 V

The order of the size of nucleus and Bohr radius of an atom respectively are

(a)

(b)

(c)

(d)

 Identify the conclusion of the photoelectric experiment from the following.

If two streams of protons move parallel to each other in the same direction, then they

(a) Do not exert any force on each other

(b) Repel each other

(c) Attract each other

(d) Get rotated to be perpendicular to each other

There are three voltmeters of the same range but of resistances 1000Ω, 8000 Ω and 4000 Ω  respectively.  The best voltmeter among these is the one whose resistance is

(a) 10000 W

(b) 8000 W

(c) 4000 W

(d) All are equally good

Magnetic dipole moment is a vector quantity directed from: