# Physics Preparatory Test for Quarterly, Class XII, –I

## Physics preparatory tests for PUC, ISc, class XII in the CBSE, ICSE (CISCE), State boards.

Subject: Physics

Test: Preparatory test — I.

Class: ISC — II (also good for PUC — II)

date: 24 the June 2013.

Time: 1.5 hours.

Total marks: 50

# Section A

Objective — 3 questions carry 1  mark each, all to be answered.

### Question 1

What’s the work done to take a charge Q on a circular voyage, on an equipotential surface?

A. Zero                                                                   B. Depends on radius of circle

C. Depends on distance from center of equipotential surface       D. $\frac{Q}{\epsilon_0}$

### Question 2

Rutherford’s atomic model is based on which fact

A. Geiger Marsden scattering of $\alpha-{particles}$ suggests presence of nucleus.

B. Smith’s electrodes dipped in electrochemical material

C. Quantization of charge     D. Quantization of angular momentum

### Question 3

Half life $T_{\frac{1}{2}}$ and decay constant $\lambda$ are related as follows

A. $T_{\frac{1}{2}}=\frac{ln \frac{1}{2}}{\lambda}$                                                                          B. $T_{\frac{1}{2}}=\frac{e^{-\lambda}}{\lambda}$

C. $T_{\frac{1}{2}}$ is a constant and does not depend on $\lambda$         D. $T_{\frac{1}{2}}=\frac{A}{Z+A}$

# Section B

Subjective — 5 questions carry 1 mark each, all to be answered.

### Question 4

Write the SI unit of electrostatic potential.

### Question 5

If half life $\big(T_{\frac{1}{2}}\big)$, of radon is $x \hspace{2pt}hrs$ and you have $100$ Radon nuclei after what time you will be having $25$ of them due to radioactive decay?

### Question 6

What’s the typical energy output range of Indian nuclear reactors?

### Question 7

Which of the following physical quantity is scalar: electric field intensity, electric potential, dipole moment?

### Question 8

Between a dipole and a point charge whose potential drops faster?

Long Answer Type — 6 out of 9 questions carry 7 marks each, answer only any two from each of the following sections, C, D or E. Draw necessary diagrams with suitable quantities and units shown across the diagram.

# Section C

### Question 9

Use superposition principle of electric field intensity of two charges, to obtain the electric field intensity E of a dipole along the dipole axis. This is known as electric field for the End-on configuration.

Also use the same idea to obtain the potential at a point vertical to the dipole axis. This is known as potential for the Broad-on configuration.

### Question 10

Obtain the electric field intensity E of a dipole vertical to the dipole axis, i.e. — Broad-on electric field. Also obtain the potential at a point on the dipole axis, i.e. — End-on potential.

### Question 11

State the Coulomb’s law of interaction for two charges in vector form. Define permittivity of free space, relative permittivity of a medium and permittivity of the medium and write the relation between them.

Define Electric flux and state Gauss law. Write 3 properties of electric lines of force. Write two properties of Gaussian surface. Write one property of equipotential surface.

# Section D

### Question 12

Describe the principle of a nuclear reactor with a suitable diagram and write the functions of its important components. Write two aspects of Nuclear Hazard.

### Question 13

State Postulates of Bohr’s atomic model. Use the angular momentum quantization in stationary orbit to obtain the quantized radius $r_n$, speed $v_n$ and energy $E_n$ electron in orbits of H-atom.

### Question 14

Starting out with the law of radioactive decay derive the expression for number of nuclei at any time as a function of initial number of nuclei and decay constant.  Derive the relation between half life $\big(T_{\frac{1}{2}}\big)$ and decay constant $\lambda$ from this.

# Section E

### Question 15

Describe the Rutherford atomic model by explaining results of Geiger Marsden scattering experiment. Draw a PE, KE, E diagram of a Rutherford H-atom. Draw the Marsden scattering experiment plot and Gold-foil $\alpha-{particle}$ deflection diagram and explain each with 1 or 2 sentences. What are the drawbacks of this model? (2 is enough)

### Question 16

Use the Bohr’s $n-th$ level energy $-\frac{13.61}{n^2}\hspace{2pt}eV$ to find the energy of absorption from $n=2 \to n=6$ state and energy of emission from $n=5 \to n=3$ state.

### Question 17

Describe the Van-de-Graaff generator, its principle, working and use.