# Physics class tests for junior college, –III

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

Subject: Physics

Test: Class test — III

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

date: 5th August 2013.

Time: 55 minutes

Total marks: 35

# Section A

Objective — 7 questions each carry 1 mark, all questions to be answered.

### Question 1

Targets in X-ray tube are made of high atomic number metals. Examples are

A. Tungsten and Platinum              B. Nickel and Chromium

C. Uranium and Plutonium            D. Sodium and Mercury

### Question 2

Electric and magnetic fields do not deflect which of the following

A. X-rays                    B. Y-rays

C. Electrons              D. Cosmic Rays

### Question 3

Why $K_a$ and $K_b$ lines are produced — chose only one appropriate answer.

A. Electronic transitions                                                           B. Atomic collisions

C. Radioactive decay                                                                  D. Nuclear transmutation

### Question 4

Exactly why there is quantization of physical variables such as momentum, angular momentum, energy, orbital distance and speed?

A. Wave-particle duality                                         B. Interference of waves

C. Particle acceleration to speed of light            D. Resistance experienced by particles in conductors

### Question 5

Cathode rays are streams of

A. Electrons                                         B. X-rays

C. Nucleons                                          D. High atomic number elements

### Question 6

Kirchhoff’s loop rule is based on?

A. Conservation of charge                 B. Conservation of energy

C. Conservation of baryon number D. Conservation of lepton number

### Question 7

Kirchhoff’s junction rule is based on?

A. Conservation of charge                 B. Conservation of energy

C. Conservation of baryon and lepton number D. Conservation of azimuthal quantum number

# Section B

Subjective — 14 questions carry 2 marks each, all to be answered.

### Question 8

If threshold frequency is $5\times 10^4$ Hz whats the work function of the metal in eV or joule?

### Question 9

3 capacitors $C = 5\hspace{2pt} \mu F$ each are in series, whats their equivalent resistance?

### Question 10

3 capacitors $C = 5\hspace{2pt} \mu F$ each are in parallel combination, whats their equivalent resistance?

### Question 11

If a potential difference of $5\hspace{2pt}V$ is applied at two ends of a $60\hspace{2pt}cm$ long metal wire with current density $j = 10^{-7}\hspace{2pt}\frac{A}{m^2}$ whats conductivity of the wire?

### Question 12

In a Wheatstone bridge if $P = 5\hspace{2pt} \Omega$ and $Q = 10 \hspace{2pt}\Omega$ are the resistors in one arm, and $R = 15 \hspace{2pt}\Omega$ what would the unknown resistor $S$ in the $2^{nd}$ arm be?

### Question 13

If work function of a metal is $50 \hspace{2pt}eV$ what would the maximum kinetic energy of any $e^{-}$ be, given a light of energy of $100 \hspace{2pt}eV$ falls on the metal? Whats the stopping potential?

### Question 14

Name 4 sources of electric power that can be harnessed for household applications.

### Question 15

If 3 cells of emf $\mathcal{E}_1, \mathcal{E}_2, \mathcal{E}_3$ are connected in series with their + and – terminals connected in sequential order and each has a back-emf $\mathcal{E}_1 ', \mathcal{E}_2 ', \mathcal{E}_3 '$ whats the equivalent emf of the series?

### Question 16

If a cell $\mathcal{E}_1 = 5 \hspace{2pt} V$ and $\mathcal{E}_2 = 5 \hspace{2pt} V$ are connected in parallel with zero internal resistance for both whats their equivalent emf?

### Question 17

For principal quantum number $n=5$ whats the speed of an electron in a hydrogen atom?

### Question 18

What would be the wavelength of a radiation of energy $50\hspace{2pt}MeV$?

### Question 19

For a free electron of speed $0.1\hspace{2pt}c$ with $c=3\times 10^8\hspace{2pt}\frac{m}{s}$ what is the de-Broglie wavelength?

### Question 20

If a conductor of length $50\hspace{2pt}cm$ and area of cross section $1\hspace{2pt}mm^2$ carries a current of $2\hspace{2pt}A$, when a battery of emf with ideal terminal voltage $50\hspace{2pt}V$ is connected across, what is the resistivity of the wire?

### Question 21

In Thomson’s e/m experiment the $e^{-}$ is going in a circle of circumference $1\hspace{2pt}m$ then whats the speed of the $e^{-}$ if the magnetic field intensity B is $10 \hspace{2pt}T$ where T ≡ Tesla, is SI unit of magnetic field intensity.