JUNE 2024 — Physics STD 12 Science — Question

Which of the following plots may represent the thermal energy produced in a resistor in a given time as a function of the electric current

(a) a

(b) b

(c) c

(d) d

There are two conductors X and Y carrying a current I and moving in the same direction. p and q are two electron beams also moving in the same direction. Will there be attraction or repulsion between the 2 conductors and between the two electron beams separately?

During a negative beta decay:

1. An atomic electron is ejected.
2. An electron which is already present within the nucleus is ejected.
3. A neutron in the nucleus decays emitting an electron.
4. A proton in the nucleus decays emitting an electron.

Carbon, silicon and Germanium atoms have four valence electrons each. Their valence and conduction band are separated by energy band gaps represented by (E_g)_C. (E_g)_Si and (E_g)_Ge respectively. Which one of the following relationship is true in their case

(a) (

(b)

(c)

(d)

An aeroplane in which the distance between the tips of wings is 50 m is flying horizontally with a speed of 360 km/hr over a place where the vertical components of earth magnetic field is 2.0 . The potential difference between the tips of wings would be

(a) 0.1 V

(b) 1.0 V

(c) 0.2 V

(d) 0.01 V

In Young's double slit experiment when wavelength used is 6000 Å and the screen is 40 cm from the slits, the fringes are 0.012 cm wide. What is the distance between the slits

(a) 0.024 cm

(b) 2.4 cm

(c) 0.24 cm

(d) 0.2 cm

Finger prints are observed by the use of

(a) Telescope

(b) Microscope

(c) Gallilean telescope

(d)  Concave lens

If  and  be the numbers of holes and conduction electrons in an extrinsic semiconductor, then

(a)

(b)

(c)

(d)  or  depending on the nature of impurity

In Bohr's model of hydrogen atom, let PE represents potential energy and TE the total energy. In going to a higher level

(a) PE decreases, TE increases	(b) PE increases, TE increases
(c) PE decreases, TE decreases	(d) PE increases, TE decreases

A solid metallic sphere has a charge +3Q. Concentric with this sphere is a conducting spherical shell having charge -Q. The radius of the sphere is a and that of the spherical shell is b(b > a). What is the electric field at a distance R(a < R  <  b)  from the centre

(a)

(b)

(c)

(d)