Wednesday, 16 May 2012

Important Questions for 2nd year Physics


NOTE: Refer all the questions from question bank with these important questions

MCG & Torque
Nuclear reactor
Half wave & full wave rectifier
Krichhoff laws & Wheatstone bridge
Formation of Stationary waves
Growth & Decay of current in L – R circuit
Laws & verification by sonometer
n-p-n & p-n-p transistor
Open pipe & closed pipe
Mass defect & binding energy curve

Doppler’s effect, source is in case (1) motion observer is at rest
Case (2) observer in motion source Is at rest
Energy stored in a capacitor
Define E & V, find relation between them
Seebeck effect, variation of thermo emf
Couple acting on a bar magnet
Force between two parallel conductors
J. J. Thomson method (e/m)
Laws of P.E.E. & Einstein equation
Zener diode
T.I.R. & working of optical fiber
Polarization by reflection & refraction
C – N & P – P cycle
Discovery of neutron
Capacitors in series & parallel
Ramsden & Huygens eyepieces
Lenz’s law
MCG in to Ammeter
MCG in to Voltmeter
Meter bridge
Pelter & Thomson effect & coefficients
X – rays
NAND & NOR Gates
P-N junction
Young’s double split
Ba on axial line
Ba on equatorial line
Duddell’s galvanometer
Moseley’s law
Defference between Fresnel & fraunhoffer
Application of Doppler effect
Define echo? Find minimum distance to here an echo
Absorption coefficient, reverberation time & Sabine’s formulae
State & explain Boit – savart law
TanA & TanB positions
Uses of radio isotopes
Applications of interference
Applications of diffraction
Applications of polarization
Vibration magnetometer


1.         Define critical angle? Mention its relationship with refractive index?
Ans:-    When the light ray passes from denser medium to air (or) vacuum, the angle of incidence in the denser medium at which the angle in air (or) vacuum is 90o is called critical angle of the denser medium Refractive index of denser medium   
2.         What are the difference between microscope and telescope?

1) It is used to see very small objects.
1) It is used to see distant objects.
2) Its objective is of smaller focal length    and of smaller aperture.
2) Its objective is of longer focal length and of larger aperture
3) Its eyepiece is of longer focal length and of larger aperture
3) Its eyepiece is of smaller focal length and of smaller aperture
4) It produces linear magnification i.e., size of the image is larger than that of the object.
4) It produces linear magnification i.e., size of the image is larger than that of the object.

3.         What are Fraunhoffer lines and what is their importance?
            Ans:-    Fraunhoffer lines are the dark lines crossing the solar spectrum.
            Importance:- The element present in sun’s atmosphere can be identified

4.         Why do diamond’s sparkle?
            Ans:- Diamonds sparkle due to total Internal Reflection.

5.         Define the magnetic momentum of a bar magnet? What is its direction?
            Ans:- Magnetic moment:- It is defined as the product of pole strength and magnetic length. It is represented by M
            M = m(2l)
            It is a vector its direction is always along south pole to north pole of the magnet
6.         Do you find two magnetic field lines intersecting? Why?
            Ans:- Two magnetic lines of force do not intersect with each other, Because if they intersect, at the point of intersection the field should possess two different directions which is impossible.
7.         What is the magnetic moment of a semi circular magnet of radius ‘r’ and pole strength ‘m’?
            Ans:- Magnetic moment is
            M = m(2r).
8.         In the equal distance method of a deflection magnetometer, the deflections produced by two bar magnets are 30o and 60o. What is the ratio of their magnetic moments?
            M1 : M2 = 1:3
9.         The electric lines of force do not intersect why?
                        Ans:- They do not intersect if they intersect, at the point of intersection intensity of electric field will act in two different directions, which is not impossible.

10.        Three capacitances , are connected in parallel (i) What is the ratio of charges? (ii) What is the ratio of potential differences?
            Ans:- In parallel combination potential differences is constant where as charge changes.

                              (ii) As potential is constant

11.        Can there be electrical potential at point with zero electric intensity?

            Ans:- Yes, electric potential is constant from the centre of a hallow spherical conductor up to the surface and is equal to     where as intensity of electrical field is zero inside the conductor.
12.        The potential earth is taken as zero? Explain?
            Ans:- Since earth is a huge conductor, an addition (or) removal of a small amount of charge does not alter its electrical conduction. So its potential is taken as zero.
13.        What is the difference between electric lines of force and magnetic lines of induction?
            Ans:- Electric lines of force are open loops where as magnetic lines of induction are closed loops.
14.        State Gauss’s law in electrostatics?
            Ans:- The total electric flux through any closed surface is equal to  times the net charge enclosed by the surface. Here  is the permittivity of free space.
15.        Repulsion is the sure test of electrification then attraction? Why?
            Ans:- A charged body may attract a neutral body and also an opposite charged body. But it always repels a like charged body. Hence repulsion is the sure test of electrification.
16.        Write down the used of capacitors?
            Ans:- (i) To store electrical charges at low potential
                        (ii) In tuning circuit of radio
                        (iii) To produce strong electric fields in small space
                        (iv) As filters to stop D.C and allow A.C
17.        What are the ohmic and non-ohmic devices?
            Ans:- Ohmic devices:- Devices that obey ohm’s law are called ohmic devices
                        Ex:- (i) All metallic conductors, at constant temperature.
                        Non-ohmic devices:- Devices that does not obey ohm’s law are called
                        Non-ohmic devices
                        Ex:- (ii) p-n junction diode, Thermistor.
18.        The manganin wire is used in the preparation of standard resistances. Why?
            Ans:- The temperature coefficient of resistance of manganin wire is very low. Hence its resistance its resistance almost remains constant at different temperatures. Hence it is used in the manufacture of standard resistance.
19.        Write two differences between emf and p.d ?
1) The difference of potential between the terminals of a cell in open circuit is emf
1) The difference of potential between the terminals of a cell in closed circuit is potential difference (P.D)
2) A source of electric current like a cell can have emf
2) Any part of a closed circuit can have potential difference (P.D)

20.        Which of the two, namely voltmeter and potentiometer is preferable to measure the emf of a battery? Why?
            Ans:- Potentiometer is preferable to measure the emf of battery.
            Voltmeter draws current from battery, while measuring its emf. But potentiometer draws no current from the battery, when potentiometer is balanced.
21.        When is the series combination of cells advantageous and why?
            Ans:- Series combination of cells is advantageous when more emf at low current is required. In series combination of cells, Where r<<R. Then
            i.e., Potential difference across the external resistance is n times emf of each cell.
22.        When is the parallel combination of cells advantageous and why?
            Ans:- Parallel combination is advantageous when more current is to be drawn at low potential.
            In parallel combination cells,               In R<<r, Then
            i.e., if external resistance is very small, current drawn is ‘n’ times that of a single cell.
23.        What is the internal resistance of a cell? Write the value of internal resistance of an ideal cell?
            Ans:- The internal resistance of a cell is the resistance of the electrolyte between the anode and cathode Internal resistance of an ideal cell is Zero
24.        What is the specific resistance of material of a conductor. Mention its units?
            Ans:- The resistivity of a material is numerically equal to the resistance of a conductor of that material having one meter length and one square meter area of cross section
Units:-  ohm meter .
25.        What is the force on a conductor of length ‘l’ carrying current ‘i’ when it is situated in a magnetic field of induction B? When is it maximum?
            Ans:- force on a current carrying conductor in a magnetic field
                        F =
                        Force is maximum when B and l are perpendicular to each other,
26.        State Fleming’s left hand rule?
            Ans:- Fleming’s left hand rule:-  Stretch the left hand such that the thumb, the fore finger and central finger are mutually perpendicular to each other. If fore finger indicates the direction of magnetic field of induction. The central finger indicates the current in the conductor. And the direction of force on the conductor is indicated by the thumb.

27.        A moving coil Galvanometer can measure a current of  What is the resistance of the shunt to measure 1A.
28.        Distinguish between ammeter and voltmeter

1) It is connected series in the circuit
1) It is connected parallel in the circuit
2) Internal resistance of ideal ammeter is zero.
2) Internal resistance of ideal voltmeter is infinity.

29.        Define coefficient of self induction, coefficient of mutual induction?
            Ans:- Coefficient of self induction  (L):- It is defined as the negative induced emf in the coil when the rate of current in the coil is unity.
coefficient of mutual induction (M):It is defined as the negative induced emf in the secondary coil when the rate of change of current in the primary is unity.

30.        What is transformer ratio?
            Ans:- Transformer ratio is equal to the number of terns in the secondary coil to the number of terns in the primary coil.
            Transformer =
31.        The current in a coil is changed from 5A to 10A in  sec. Then, an emf of 50 mV is induced in a coil near by it calculate mutual inductance of two coils.
            Ans:-  sinduced emf, e = 50 mV, M = ?
            From e = M di/dt M = 100
32.        What is work function of a metal?
            Ans:- The minimum amount of energy required to remove an electron from the surface of a photo sensitive metal is defined as the work function of that metal.
33.        What is Compton effect? Explain?
            Ans:- When X-rays are scattered by any substance, then the wavelength of some of the scattered X-rays is grater than the wave length of incident X-rays. This phenomenon is known as Compton effect.
34.        If an electron and proton have same DeBroglie wavelength, which has more momentum and kinetic energy?
            Ans:-  Both electron and proton have same momentum ()
            Electron has more kinetic energy
35.        State Moseley’s law. What is its importance.
            Ans:- The square root of the frequency of any given spectral line in the characteristic X-ray spectrum is directly proportional to the atomic number of the target.
            i.e., .
            Importance : It helped in the rearrangement of elements according to their atomic numbers and perfecting periodic table.
36.        What are isotopes and isobars?
            Ans:- Isotopes: The nuclei having the same atomic number(Z) but different mass numbers (A) are called Isotopes.
            Isobars : The nuclei having the same mass number(A) but different atomic numbers(A)
37.        What are the characteristics of radioactivity?
            Ans:- 1) Decay constant 2) Half life period
38.        What are radio isotopes? Give some examples of radio isotopes.
            Ans:- The isotopes produced in a Nuclear Reactor are called Radio Isotopes.
39.        State any two properties of neutron?
Ans:- i) Neutron is an uncharged practical and hence it is not deflected by either electrical or magnetic fields.
ii) It has very high penetrating power and has very low ionizing power
40.        What are the majority and minority charge carriers in p-type semi conductors?
            Ans:- In p-type semiconductor, holes are the majority charge carriers and electrons are the minority charge carriers.
41.        How a battery is connected to a junction diode in (i) forward and (ii) reverse bias?
            Ans:- In forward bias positive terminal of the battery connected to the p-region and negative terminal to the n-region of the p-n junction diode
            In reverse bias positive terminal of the battery connected to the n-region and negative terminal to the p-region of the p-n junction diode
42.        Which gates are called universal gates?
            Ans:- NOR gate and NAND gate are called as universal gates.

43.        Draw the circuit symbols for p-n-p & n-p-n Transistros?
            Ans:- p-n-p- Transistor                                       n-p-n Transistor
44.        What is n-type semiconductor? What are the majority and minority charge carriers in it?
            Ans:- Pentavalent impurities are doped with intrinsic semiconductor is called n-type semiconductor.
            Majority charge carriers are electrons and Minority charge carriers are holes.
45.        What are intrinsic and extrinsic semiconductors?
            Ans:- Pure semiconductors are called Intrinsic semiconductors
                      Doped semiconductors are called Extrinsic semiconductors.
46.        What are the basic blocks of a communication system?
            Ans:- The basic blocks of a communication systems are (i) Transmitter
            (ii) Communication channel        (iii) Receiver
47.        What is the sky wave propagation?
            Ans:- In the frequency range from a few MHz up to about 30 MHz, long distance communication can be achieved back by ionosphere reflection of radio waves back towards the earth. This mode of propagation is called sky wave propagation and it is used by short wave broadcast services.
48.        Define modulation. Why is it necessary?
            Ans:- The process of combining audio frequency signal with high frequency signal is called modulation.
            Need of modulation: To separate audio frequency signal with millions of low frequency in the atmosphere.
49.        What is “World Wide Web” (W.W.W)?
            Ans:- It is an encyclopedia of knowledge accessible to every one round the clock throughout the year.
50.        Mention the frequency range of speech signals?
            Ans:- Frequency range of speech signals is 300Hz to 3100Hz.

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