Nuclei — Physics STD 12 Science — Question

Ten grams of ⁵⁷Co kept in an open container beta-decays with a half-life of 270 days. The weight of the material inside the container after 540 days will be very nearly:

The addition of antimony atoms to a sample of intrinsic germanium transforms it to a material which is

(a) Superconductor	(b) An insulator
(c) N-type semiconductor	(d) P-type semiconductor

When a straight wire is moved up and down rapidly between two poles of a horseshoe magnet then _______ is produced in the wire.

 Pick out the correct increasing order of energy of electromagnetic waves from the following:

Three positive charges of equal value q are placed at the vertices of an equilateral triangle. The resulting lines of force should be sketched as in

(a)

(b)

(c)

(d)

Antimony and bismuth are usually used in a thermocouple, because

(a) Negative thermal e.m.f. produced	(b) Constant thermal e.m.f. produced
(c) Lower thermal e.m.f. produced	(d) Higher thermal e.m.f. produced

A wave moving in a gas,

1. Must be longitudinal
2. May be longitudinal
3. Must be transverse
4. May be transverse

Electric field and magnetic field in Thomson mass spectrograph are applied

(a) Simultaneously, perpendicular	(b) Perpendicular but not simultaneously
(c) Parallel but not simultaneously	(d) Parallel simultaneously

Electric conduction in a semiconductor takes place due to: