Magnetism And Matter — Physics STD 12 Science — Question

A wire can sustain the weight of 20kg before breaking. If the wire is cut into two equal parts, each part can sustain a weight of.

1. 10kg
2. 20kg
3. 40kg
4. 80kg.

The voltage gain of a triode depends upon

(a) Filament voltage

(b) Plate voltage

(c) Plate resistance

(d) Plate current

A prism ABC of angle 30° has its face AC silvered. A ray of light incident at an angle of 45° at the face AB retraces its path after refraction at face AB and reflection at face AC. The refractive index of the material of the prism is

(a) 1.5

(b)

(c)

(d)

Two identical thin rings each of radius R meters are coaxially placed at a distance R meters apart. If Q₁ coulomb and Q₂ coulomb are respectively the charges uniformly spread on the two rings, the work done in moving a charge qfrom the centre of one ring to that of other is

(a) Zero

(b)

(c)

(d)

Earth’s magnetism was discovered by:

Two photons having _________________:

Mutual inductance of two coils is M. If current change in time t in first coil is I, then induced emf in the second coil is:

An image of the sun is formed by a lens of focal length of 30 cm on the metal surface of a photoelectric cell and a photoelectric current I is produced. The lens forming the image is then replaced by another of the same diameter but of focal length 15 cm. The photoelectric current in this case is

(a)

(b) I

(c) 2I

(d) 4I

The potential gradient at which the dielectric of a condenser just gets punctured is called

(a) Dielectric constant

(b) Dielectric strength

(c) Dielectric resistance

(d) Dielectric number