SAMPLE PAPER

PHYSICS

SET-II

Time Allowed : 3 Hours

Maximum Marls : 70

General Instructions :

(i) All questions are compulsory.

(ii) Marks for each question are indicated against it.

(iii) Question numbers 1 to 8 are very short-answer questions, carrying 1 mark each. There are to be answered in one or two sentences.

(iv) Question numbers 9 to 18 are short - answer questions, each carrying 2 marks. Answer to these questions should be around 30 words each.

(v) Question numbers 19 to 27 are also short-answer questions, each carrying 3 marks. Answer to these questions should be around 50 words each.

(vi) Question numbers 28 to 30 are long-answer questions, each carrying 5 marks. answer to these should be around 150 words.

(vii) Use log tables, if necessary.

Define atomic mass unit (amu). Write the energy equivalent of atomic mass unit in Mev.

Why does the electrical field inside a dielectric decreases when it is placed in an external electric field ?

State any rule which relates the direction of electric current and the direction of accompanying magnetic field.

What is the phase difference between the voltage drop across L and C in a series LCR circuit connected to an ac source ?

Arrange the following radiations in descending order or their wavelengths.

Radio waves, X rays, ultra violet rays, red light.

A transistor is being used as a common emitter amplifier. What is the value of phase difference, if any, between the collector emitter voltage and the input signal ?

Two wires A and B of the same material having same length have their cross sectional area in the ratio 1: 4. what would be the ratio of heat produced in these wires when same voltage is applied across each ?

Why does the conductivity of a semiconductor increase with the rise in temperature ?

Define the term critical angle for a given pair of media. Establish its relationship with relative refractive index.

Observation on a given device yielded the following current - voltage data.

Draw V-I graph using the above data. What conclusion can you draw from the graph with regard to ohmic or non-ohmic nature of the device ?

Suppose you have two bars of identical dimensions one made of paramagnetic substance and the other of diamagnetic substance. If you place these bars along a uniform magnetic field, show diagramatically, what modifications in the field pattern would take place in each case.

What are thermal neutrons ? Why are neutrons considered as ideal particles for nuclear fission ?

Calculate the equivalent capacitance between the points A and B in the following combination.

A wire of resistance 4 R is bent in the form of a circle. What is the effective resistance between the ends of a diameter?

A magnetised needle in a uniform magnetic field experiences a tongue but no net force. However an iron nail near a bar magnet experiences a force of attraction in addition to a torque. Explain.

L and a resistor R connected in parallel to a battery through a switch. The resistance of R is the same as that of the coil that makes L. Two identical bulbs are put in each arm of the circuit.

(i) Which of the bulbs lights up earlier when S is closed ?

(ii) Will the bulbs be equally bright after some time ?

A convex lens made up of a material of effective index µ 1 is immersed in a medium of refractive index µ 2 - Trace the path of a parallel beam of light passing through the lengs when :

(i) µ 1 = µ2

(ii) µ1 < µ2

The wavelllength of the second line of the Balmer series in Hydrogen spectrum is 4861 A⁰. Calculate the wavelength of the first time.

With the help of a circuit diagram explain how can you find the internal resistance of a primary cell. Derive the necessary formula.

State and Explain Huygen's principle. Name the type of wave front that corresponds to a beam of light

(i) Coming from a very far off source.

(ii) Diverging raidally from a point source.

Draw the logic symbol and the truth table of an OR gate. Describe its realisation with circuit diagram using semiconductor diode.

How will you determine the temperature of the Sun ? Derive the necessary formula.

A student has two wires of iron and copper of equal length and diameter. He first joins the two wires in series and passes electric current through the combination which increases gradually. After that he joins the two wires in parallel and repeats the process of passing the current. Which wire will glow first in each case and why ?

A sunshine recorder globe of 30 cm diameter is made of glass of refractive index µ = 1.5. A ray enters the globe parallel to the axis. Find the position from the centre of the sphere where the ray crosses the axis.

Difference between n-type and p-type semiconductors on the basis of energy band diagram. Explain the process of conduction in both type of materials.

The frequency of a cyclotron Oscillator is 10⁷ Hz. What should be the operating magnetic field for accelerating protons ? If the radius of the dees of the cyclotron is 6 x 10^-1 m. Calculate the energy of the proton beam produced in Mev.

A narrow monochromatic beam of light of intensity I is incident on a glass plate. another identical glass plate is kept close to the first one and parallel to it. Each plate reflelcts 25 % of the incident light and transmits the remaining. Calculate the ratio of minimum and maximum intensity in the interference pattern formed by two beams obtained after reflectino from each plate.

With the help of a labelled diagram explain the principle, construction and working of an a.c. generator.

With the help of a labelled diagram explain the principle, construction and working of a step up transformer. Why is the core laminated ?

A glass rod rubbed with silk is brought close to two uncharged spheres in contact with each other inducing charges on them as shown in figure. Show with diagram in each case. What happens when

(i) The spheres are slightly separated ?

(ii) The glass rod is subsequently removed ?

(iii) The spheres are separated far apart ?

A photon of wave length 3310 A⁰ falls on a photocathode and an electron of energy 3 x 10^-19 J is ejected. If the wavelength of the incident phonton is changed to 5000 A⁰, the energy of the ejected electron is 7.91 x 10^-20 J. Calculate the value of Plank's constant and threshold wavelength of the photon.