### Access RBSE/CBSE Sample Paper 2018

## सी.बी.एस.ई. भौतिक विज्ञान-द्वितीय में सबसे महत्वपूर्ण प्रश्न पत्र - 2018 नमूना प्रश्न

#### SECTION A (1 Mark )

`Q.1`

Why Cyclotron is not suitable to accelerate electron ?

`Q.2`

Draw Hysteresis curve for permanent magnet and electromagnet.

`Q.3`

Figure shows planar loops of different shapes moving out of or into a region of magnetic field which is directed normal to the plane of loops downwards. Determine the direction of induced current in loop (i) and (ii) using Lenz’s law.

`Q.4`

Why is short wave band used for long distance Radio Broadcast?

`Q.5`

If a wire is stretched to double its original length without loss of mass, How will the resistivity of the wire be influenced ?

#### SECTION B (2 Marks )

`Q.6`

Draw the energy level diagram showing the emission of β -particles followed by γ-rays by a 60/27 Co nucleus.

`Q.7`

Suggest a suitable method and draw diagram to invert an image

(i) Without change in size.

(ii) Without change in size and without deviation from its original direction of view.

`Q.8`

Define self inductance. Derive expression for magnetic energy stored in inductor when current I passes through it.

`Q.9`

Draw a plot showing the variation of (i) Electric field (ii) Electric potential due to point charge Q.

Find Expression for energy stored in capacitor then find expression for energy density of parallel plate capacitor.

`Q.10`

Find the value of current *I* in the circuit shown in fig.

#### SECTION C (3 Marks )

`Q.11`

Find expression for capacitance of parallel plate capacitor having dielectric plate of thickness t.

`Q.12`

(a) Why are coherent source necessary to produce a sustained interference pattern?.

(b) In Young’s double slit experiment using monochromatic light of wavelength the intensity of light at a point on the screen where path difference is is K units. Find out the intensity of light at a point where path difference is /3.

`Q.13`

Figure shows a small magnetized needile P placed at a point O. The arrow shows the direction of its magnetic moment the other arrow show different positions of another identical magnetized needle Q.

(a) Compare and contrast Biot–Savart law with coulomb’s law.

(b) In which configuration is the system in
(i) Stable (ii) Unstable equilibrium

(c) Which configuration corresponds to the lowest potential energy.

`Q.14`

Derive an expression for the impedance of a series LCR circuit connected to an AC supply of variable frequency. Plot a graph showing variation of current with thr frequency of applied voltage. Then explain use of resonance in the circuit for the tuning mechanism of radio or TV set.

`Q.15`

Define the terms

(i) 'cut-off voltage' and

(ii) 'threshold frequency' in relation to the phenomenon of photoelectric effect.

Using Einstein's photoelectric equations show how the cut-off voltage and threshold frequency for a given photosensitive material can be determined with the help of a suitable plot/graph.

`Q.16`

(a) Why photodiode used preferably in reverse bias condition. A photo diode is fabricated from a semiconductor with band gap of 2.8eV. Can it detect a wavelength using 6000nM. Justify.

`Q.17`

The energy level diagram of an element is given below. Identify, by doing necessary calculations, which transition corresponds to the emission of a spectral line of wavelength 102.7 nm.

`Q.18`

Explain Sky Wave propagation in detail. Also give condition for sky wave propagation.

Give short note on following

(i) Attenuation

(ii) Repeater

(iii) Tranducer

`Q.19`

Find the energy equivalent of one a.m.u. in joule and MeV.. Draw graph to show BE/A and mass number relation.

`Q.20`

A voltage of 283 peak value and 50 HZ is applied to a series LCR circuit in which R = 3 Ω, L = 25.48 mH and C = 796 µ F. Find

(a) the impedance of the circuit

(b) phase different between voltage and current.

(c) the power dissipation

(d) Power factor

(e) What is the frequency of the source at which resonance occurs.

(f) Calculate the impedance, current and the power at resonant condition

`Q.21`

Find the position of the image formed by the lens combination.
Focal length of respective lenses are +10, -10 and + 30 cm

`Q.22`

What do you mean by ideal electric dipole. Derive expression for electric field due to dipole on axial line.

#### SECTION D (4 Marks )

`Q.23`

Rajesh (B.A. Student) and Raman (B.Sc. Student) were going on a vacation in their Car. On their way Rajesh noticed that a truck carrying inflammable material was going ahead with metallic chains hanging from the bumper and touching the road. He was surprised and thought what type of decoration it was. He pointed it out to The Raman. Raman explained him the cause and told it is necessary and safe for Truck.

(a) What are the values shown by Raman associated with above statement.(at least Three)

(b) In your opinion What explanation Raman would have given ?

(c) What possible damages are possible in absence of this arrangement ?

#### SECTION E (5 Marks )

`Q.24`

(a) State the principle of P-N diode as a rectifier. Draw sketch of input and output waveform indicating clearly the function of the two diodes used.

(b) Two signals A, B are given below, are applied as input to (i) AND (ii) NOR and (iii) NAND Gates. Draw the output wave-form in each case.

(a) Draw the circuit diagram of a common emitter amplifier using an NPN transistor. What is the phase difference between input and output voltage ? Draw the input and output wave form,. Write an expression for its voltage gain. State two reasons Why a common emitter amplifier is preferred to a common base amplifier.

(b) The input resistance of a silicon transistor is 665 ohm. Its base current is changed by 15 micro amp which results in a change of 2 mA in the collector current. The transistor is used as a common emitter amplifier with a load resistance of 5 K Ohm. What is the voltage gain of the amplifier ?

`Q.25`

(a) Using Biot – Savart law, derive expression for the magnetic field in the vector form at a point on the axis of circular current loop.

(b) A toroid has a core (non-ferromagnetic) of inner radius 25 cm and outer radius 26 cm around which 3500 turns of a wire are wound. If the current in the wire is 11 A, what is the magnetic field

(i) outside the toroid

(ii) inside the core of the toroid

(iii) in the empty space surrounded by the toroid?.

(a) Draw a labelled diagram of a moving coil galvanometer. State the principle on which it works. Why it is needed radial magnetic field..

(b) Two moving coil meters M_{1} and M_{2} have the following particulars Two moving coil meters M_{1} and M_{2} have the following particulars.

R_{1} = 10 Ω n_{1} = 30,

compare current sensitivity and voltages sensitivity. What will be change in current and voltage sensitivity if we double the number of turns.

`Q.26`

(a) State the assumption and sign convention in deriving the lens maker formula explain refraction at convex spherical surface from rarer to denser

(b) Double-convex lenses are to be manufactured from a glass of refractive index 1.55, with both faces of the same radius of curvature. What is the radius of curvature required if the focal length of the lens is to be 20 cm?

(a) What do you mean by diffraction. Derive expression for maxima and minima in single slit diffraction pattern. Compare interfe+rence and diffraction Intensity.

(b) What do we understand by 'polarization' of a wave? How does this phenomenon help us to decide whether a given wave is transverse or longitudinal in nature?