Electric Charges and Fields — Physics STD 12 Science — Question

Mass of earth has been determined through

(a) Use of Kepler's  constancy law

(b) Sampling the density of earth's crust and using R

(c) Cavendish's determination of G and using R and 'g' at the surface

(d) Use of periods of satellites at different heights above earth's surface

Bonding in a germanium crystal (semi- conductor) is

(a) Metallic

(b) Ionic

(c) Vander Waal's type

(d) Covalent

Cathode rays are produced when the pressure is of the order of

(a) 2 cm of Hg

(b) 0.1 cm of Hg

(c) 0.01 mm of Hg

(d) 1 μm of Hg

A constant current i is maintained in a solenoid. Which of the following quantities will increase if an iron rod is inserted in the soleniod along axis?

If velocity of a particle is 3 times of that of electron and ratio of de brogile wavelength of particle to that of electron is 1.814×10⁻⁴. The particle will be:

A particle of charge q and mass m moves in a circular orbit of radius r with angular speed ω. The ratio of the magnitude of its magnetic moment to that of its angular momentum depends on

(a) ω and q

(b) ω q and m

(c) q and m

(d)  ω and m

In a charge free region, electric field lines can be taken to be continuous curves:

The minimum wavelength of photon is 5000 Å, its energy will be

(a) 2.5 eV

(b) 50 V

(c) 5.48 eV

(d) 7.48 eV

Which of the following electromagnetic waves have minimum frequency

(a) Microwaves

(b) Audible waves

(c) Ultrasonic waves

(d) Radiowaves

A 100 mH coil carries a current of 1 ampere. Energy stored in its magnetic field is

(a) 0.5 J

(b) 1 J

(c) 0.05 J

(d) 0.1 J