Physics (Abroad) Question Paper 2019 (Set-3)

General Instructions:

1. All questions are compulsory. There are 27 questions in all.
2. This question paper has four sections: Section A, Section B, Section C and Section D.
3. Section A contains five questions of one mark each, Section B contains seven questions of two marks each, Section C contains twelve questions of three marks each, and Section D contains three questions of five marks each.

1. There is no overall choice. However, internal choices have been provided in two

questions of one mark, two questions of two marks, four questions of three marks and three questions of five marks weightage. You have to attempt only one of the choices in such questions.

1. You may use the following values of physical constants wherever necessary.

<math>c = 3 \times 10^8 \text{ m/s}</math>

<math>h = 6.63 \times 10^{-34} Js</math>

<math>e = 1.6 \times 10^{-19} C</math>

<math>u_0 = 4\pi \times 10^{-7} \text{ T m A}^{-1}</math>

<math>\varepsilon_0 = 8.854 \times 10^{-12} \,\mathrm{C}^2 \,\mathrm{N}^{-1} \,\mathrm{m}^{-2}</math>

<math>4\pi\varepsilon_0 = 9 \times 10^9 \text{ N m}^2 \text{ C}^{-2}</math>

<math>m_e = 9.1 \times 10^{-31} \text{ kg}</math>

mass of neutron = <math>1.675 \times 10^{-27}</math> kg

mass of proton = <math>1.673 \times 10^{-27}</math> kg

Avogadro's number = <math>6.023 \times 10^{23}</math> per gram mole

Boltzmann constant = <math>1.38 \times 10^{-23} \text{ JK}^{-1}</math>

Q.1. Plot a graph of stopping potential <math>(V_0)</math> versus the frequency (v) of incident radiation in photoelectric emission.

Solution:

Stopping potential

<math>V_0</math> <math>\nu_0^1</math>

(frequency)

<math>v_0, v_0'</math>: Threshold frequency

Q.2 Name the charge carries for the flow of current in a (i) conductor and (ii) electrolyte.

Solution: Change carries for the flow of current in:

1. Conductor:- Electrons
2. Electrolyte:- lons.

Q.3. Why are the antennas in space wave mode of propagation generally mounted at heights of many wavelengths above the ground?

Solution. The antennas in space wave mode of propagation generally mounted at the height of many wavelengths in order to prevent waves from touching the earth curvature thus preventing attenuation and loss of signal strength.

Q.4. Two identical conducting balls A and B have charges <math>\neg Q</math> and <math>+3Q</math> respectively. They are brought in contact with each other and then separated by a distance d apart. Find the nature of the Coulomb force between them.

OR

A metallic spherical shell has an inner radius <math>R_1</math> and outer radius <math>R_2</math>. A charge Q is placed at the center of the shell. What will be the surface charge density on the (i) inner surface, and (ii) outer surface of the shell?