Moving Charges and Magnetism — Physics STD 12 Science — Question

Consider an electron (m = 9.1   confined by electrical forces to move between two rigid walls separated by 1.0  metre, which is about five atomic diameters. The quantised energy value for the lowest stationary state is

(a) 12

(b) 6.0

(c) 6.0

(d) 6 Joule

An electron passing through a potential difference of 4.9 V collides with a mercury atom and transfers it to the first excited state. What is the wavelength of a photon corresponding to the transition of the mercury atom to its normal state

(a) 2050 Å

(b) 2240 Å

(c) 2525 Å

(d) 2935 Å

The angular momentum of the electron in hydrogen atom in the ground state is:

On increasing the temperature of a conductor, its resistance increases because

(a) Relaxation time decreases	(b) Mass of the electrons increases
(c) Electron density decreases	(d) None of the above

A permanent magnet

(a) Attracts all substances

(b) Attracts only magnetic substances

(c) Attracts magnetic substances and repels all non-magnetic substances

(d) Attracts non-magnetic substances and repels magnetic substances

The element which was observed in solar spectrum is:

Two point charges 2 C and -6 C attract each other with a force of 12 N. A negative charge of 2 C is added to each of the above charges, now the force between them is:

Assertion : Ultraviolet radiation are of higher frequency waves are dangerous to human being.

Reason    : Ultraviolet radiation are absorbed by the atmosphere

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

At a place, the horizontal and vertical intensities of earth's magnetic field is 0.30 Gauss and 0.173 Gauss respectively. The angle of dip at this place is

(a) 30°

(b) 90°

(c) 60°

(d) 45°