Electric Charges and Fields — Physics STD 12 Science — Question

In the following common emitter configuration an NPN transistor with current gain b = 100 is used. The output voltage of the amplifier will be

(a) 10 mV

(b) 0.1 V

(c) 1.0 V

(d) 10 V

An electron in the n = 1 orbit of hydrogen atom is bound by 13.6 eV energy is required to ionize it is

(a) 13.6 eV

(b) 6.53 eV

(c) 5.4 eV

(d) 1.51 eV

A bar magnet of magnetic moment M is cut into two parts of equal length. The magnetic moment of either part is :

Work function of lithium and copper are respectively 2.3 eV and 4.0 eV. Which one of the metal will be useful for the photoelectric cell working with visible light ? (h = 6.6 × 10^–34 J-s, c = 3 × 10⁸ m/s)

(a) Lithium

(b) Copper

(c) Both

(d) None of these

Einstein got Nobel prize on which of the following works

(a) Mass-energy relation	(b) Special theory of relativity
(c) Photoelectric equation	(d)  (a) and (b) both

The direction of current in an iron-copper thermocouple is

(a) From copper to iron at the hot junction	(b) From iron to copper at the hot junction
(c) From copper to iron at cold junction	(d) No current will flow

Kilowatt hour is the unit of :

The value indicated by Fermi energy level in an intrinsic semiconductor is:

Two ions having masses in the ratio 1 : 1 and charges 1 : 2 are projected into uniform magnetic field perpendicular to the field with speeds in the ratio 2 : 3. The ratio of the radii of circular paths along which the two particles move is

(a) 4 : 3

(b) 2 : 3

(c) 3 : 1

(d) 1 : 4

A particle of mass M and charge Q moving with velocity    describes a circular path of radius R when subjected to a uniform transverse magnetic field of induction B. The work done by the field when the particle completes one full circle is

(a) BQv2πR

(b)

(c) Zero

(d) BQ