Atoms — Physics STD 12 Science — Question

A signal emitted by an antenna from a certain point can be received at another point of the surface in the form of

(a) Sky wave

(b) Ground wave

(c) Sea wave

(d) Both (a) and (b)

We have a galvanometer of resistance 25 Ω. It is shunted by a 2.5 Ω wire. The part of total current that flows through the galvanometer is given as

(a)

(b)

(c)

(d)

The period of oscillations of a magnet is 2 sec. When it is remagnetised so that the pole strength is 4 times its period will be

(a) 4 sec

(b) 2 sec

(c) 1 sec

(d) 1/2 sec

A 10 metre wire kept in east-west falling with velocity 5 m/sec perpendicular to the field 0.3 .  The induced e.m.f. across the terminal will be

(a)  0.15 V

(b) 1.5 mV

(c)  1.5 V

(d) 15.0 V

Energy required for the electron excitation in Li++ from the first to the third Bohr orbit is:

The value of Curie temperature for Ni is nearly:

Venus appears brighter than other stars because

(a) It is heavier than other planets

(b) Its density is more than other planets

(c) It is nearer to earth in comparison to other planets

(d) Nuclear fusion takes place at its surface

The idea of matter waves was given by

(a) Davisson and Germer

(b) de-Broglie

(c) Einstein

(d) Planck

Which device is used to produce electricity? Describe with a neat diagram.