EXPECTED QUESTIONS FOR +2 HSS Physics HSS,Important notes & - TopicsExpress

EXPECTED QUESTIONS FOR +2 HSS Physics HSS,Important notes & question papers Ctd. PUTHRAN’S Centre for PHYSICS , Behind Govt: Hospital, MANNAR 0479-2313988, 09656661146 ,09895739984 17.The direction of magnetic field is obtained either by using Cork Screw Rule or Right Hand Grip rule (a)State any one of the above rules (b)An electric current is flowing due south along a power line. What is the direction of the magnetic field. (i) above it (ii) Below it Ans; i) above east to west ii) below west to east 18.Just as Coulomb’s law in electrostatics, we have inverse square law in magnetostatics. (a)State the law Ans; search logritham table (b)Repulsion is the sure test of magnetism. Comment Ans;a magnet can attract all magnetic materials but repulsion is only b/w like poles .So (c)What is the value of dip at the equator Ans; zoro 19.The magnetic field due to current carrying conductor can be determined by a famous law (a)State the law Ans;State Laplaces law / Biot-Savarts law (b)State the rule which helps to find the direction of magnetic feild acting at a point near a current carrying conductor Ans;State Cork Screw Rule or Right Hand Grip rule (c)How will the magnetic field intensity at the centre of a circular coil carrying current charge if the current through the coil is doubled and the radius of the coil is halved? Ans; 4 times. calculte (d)The SI unit of magnetic field is (i)gauss (ii)Tesla (iii)Am2 (iv)A-m Ans: ii) Tesla 20.On the basis of magnetic properties, substances are classified into three (a)What are these classification? Ans; dia, para and ferro (b)Distinguish b/w then with at least 3 properties each (c)Which is more suitable for an electromagnet (i)Steel (ii)alnico (iii)Soft iron (iv) cobalt Ans; Alnico. they have high coercivity, get magnetised even in week magnetic field. 21.The value of intensity of magnetism is small and positive for a specimen. (a)Is it diamagnetic, Paramagnetic or ferro magnetic? Ans; Ferro magnetic (b)Give the importance of Curie point in magnetism Ans; At Curic point (temperature) ferro magnetic becomes paramagnetic . 22.Two parallel straight long conductors1&2 carry currents I1, and I2 in the same direction. a)What is the magnetic field produced by 1 at a point on2? Ans; Biot -Savarts equation. (b)Obtain as expression for force between these 2 parallel conductors. Ans; give the equation & explain the terms.Force is attractive (c)What will be the nature of the force when the current I2 is reversed Ans; Force will be repulsive 23.Laws of electromagnetic induction are (i)Faraday’s laws and (ii)Lenz’s law (a)Which of these laws find application in electric breaks of vehicles. Ans; (ii)Lenz’s law (b)Self induction of a solenoid is 1 henry. What do you mean by this statement. Ans;If the rate of change of current of 1Ampper second indeses an emf of 1Volt in a coil, the inductance of that coil is called 1H. (c) A magnet is moved in the direction top to bottom between two coils Suggest the direction of current in each coil. Ans; Anti-clockwice in the first ciol and clockwice in the second coil (d)An inductor of inductance L carries a current i. Express the energy stored in the inductor. Ans; Energy= Li2/2 24.The flow of current through one of the coil induces on instantaneous emf in the other (a)Mention the above property of the coil Ans;Mutual induction. (b)State the property Ans;In the case of two coils which are plased close to each other,but without touching, if the current passing throuh one of them changes,an emf is induced on the other (c)An emf of 100mV is induced in a coil when the current in the neighbouring coil charges from 15A to 5A in 1/5 sec. Calculate the mutual inductance of the coil Ans; Induced emf =M. change in current / time M= induced emfXtime/chnge in current 25. A bulb connected in an electrical circuit. (a)When the key is switched On the bulb obtains maximum glow only after a shorter interval of time which property of solenoid is responsible for the delay? Ans; Self induction (b)If the flux linked with the solenoid changes from 0 to 1 Weber in 2 sec.Find the induced emf in the solenoid Ans; induced emf = change in magnetic flux / time E = (1-0)/ 2 =1/2 =0.5 V (c)If the 3V battery is replaced by an ac source with the key closed, what will be the observation? Justify your answer Ans; Bulb will glow, because bulb works on heating effect of current and independent on direction of current. 26.The sharpness of resonance of a circuit is described by its quality factor (Q-factor) (a)What do you mean by Q-factor Ans; Q-factor = sharpness of resonance ie. the narrowness of the frequency band around the resonance at which the responce of an electric circuit. Q-factor= inductive reactance (Lw) / Resistance(R) (b)Write the expression for Q-factor in terms of half power frequencies. Ans; Q -factor = inductive reactance (Lw) / Resistance(R) (c)Obtain the resonant frequency and Q-factor of a series LCR circuit with L=3H, C=27 mF and R=7.4W Ans; f= --- equation for resonant frequency & calculate 27.Draw an ac Circuit passing alternating voltage V=Vrmsinwt. applied to a pure resistor. (a)What is the instantaneous value of current? Ans; nstantaneous value of current = I= V/R = Vrmsinwt / R = Irms sinwt (b) What is the instantaneous value of power? Ans; Power = current x voltage = VxI= Vrmsinwt x Irms sinwt (c)Obtain an expression for average power in one complete cycle (take average value of cosine function for one complete cycle is zero) Ans; Derivation 28.Cyclotron is a particle accelerator, which works on the basis of Lorentz force. (a)Which one of the following elementary particle can not be accelerated using cyclotron i. Electron ii. Proton iii. Neutron iv. a-particle Ans; iii. Neutron ,because it is neutral (b)Explain how does the cyclotron accelerate a particle when the electric field between the “dees” interchange Ans; At any instant a proton is ejected from the source.One of the dees is +ve and other is -ve which are placed in a strong magnetic field. Proton is accelerated towards the +ve dee whics moves perpendicular to the magnetic field and will rotate. When it comes b/w the dees, the polarity changes and is again attracted towards the other dee.This process continues and the particle gets accelerated. (c)Particles like electrons are not practically accelerated using a cyclotron to very high energies. Comment on this. Ans; mass of electron is very less.So speed of electrons become very high and uncontrolable. . 29.Capacitor blocks dc but allows ac to flow through it. (a)Comment on the above statement Ans; (b)At what conditions an LCR circuit behaves like a pure resistive circuit. Ans; At resonance Z=R. when Lw = 1/ Cw (c)Obtain an expression for resonant frequency Ans; Derivation 30.Electromagnetic spectrum consists of orderly distribution of electromagnetic waves. (a)Name the electro-magnetic wave used for studying the crystal structure of solids Ans; X-rays (b)Mention any three properties of electromagnetic waves Ans; transverse waves, velocity = velocity of light,the planes of oscillationof electric and magnetic fields are perpendicular to each other,they follow superposition principle. 31.A light ray travels from a denser to a rarer medium. (a)If the angle of incidence is equal to critical angle, how the ray travels? Ans; At Critical angle refracted light ray gest graces the surface of seperation. ie angle of refraction =90 (b) If the angle of incidence is greater than the critial angle, how the ray travels? Ans;refracted light ray reflected to the denser medium. (c)What is the phenomenon called Ans; total internal reflection (d) Under what condition this phenomenon take place? Ans; i) light ray passes from denser to rarer medium. ii)angle of incidence is greater than the critial angle 32.You are given three electromagnetic waves. U-V rays, X-rays, Yellow light (a)Arrange them in the decreasing order of wavelength Ans;( see the logaritham table page 72) (b)What is the contribution of green house effect in controlling the earth’s surface temperature Ans; Maintaining the temperature of earths atmosphere. 33.Light waves are found to be transverse in nature. (a)Which phenomenon established the transverse nature of light? Ans;Huygens theory. Wave nature (b)What is the working principle of polanoids? Ans;Polarisation. (c) State he principle Ans;When an ordinary light is passing through a polaroid,the vibrations are confined only in one direction. (d)Show that at the polarising angle the reflected and refracted rays are mutually perpendicular to each other Ans; refer text book 34.The apparent depth of a tank of water change if viewed obliquely a)Which is the phenomenon behind it Ans;Refraction. The bending of light ray, when passes from one medium to another b)Explain the law related with the phenomenon Ans;State the laws of refraction c)A small bulb is placed at the bottom of the tank containing water to depth of 75cm. What is the area of the surface of water through which light from the bulb can emerge out? Refractive index of water is 1.33 Ans; R= depth/root of squre of( refrctive index -1) Area of athe circle= 35.A student uses a simple microscope to view smaller objects. Is it possible for him to get a highly magnified image with a simple microscope? (a)What is your opinion? Justify your answer. (b)Draw the diagram of a device which gives highly magnified image Ans; Compound microscope. fig Explanation (c)Arrive at an expression for the magnifying power of the device Ans; Derivation ( atleast equation with terms) 36. The refraction at a spherical surface from a medium of refractive index n1 to medium of refractive index n2 is governed by the equation –n1/u + n2/v n2-n1)/R (a)Using the above given relation, arrive at Lensmaker’s formula (b)What is Thin lens formula (law of distance for a lens) (c)A converging lens of power 5D and a diverging lens of Power 2D are kept in contact. Calculate the focal length of the combination 37.Nature manifests herself in two fundamental forms-matter and energy. (a)What is the rest mass of a photon Ans; see Clarks table page 105 (b)Write the expression for de-Broglie wavelength and explain the letters in the expression Ans; wavelength = h/mv where h-planks constant m- mass of particle, v-velocity of particle (c)Show that de-Broglie wavelength of electrons energy E is h/ (root of 2meV) 38. Show a version of Young’s experiment performed by directing a eam of electron on a double slit. The screen reveals a pattern of bright and dark fringes similar to an interference as pattern produced when a beam of light is used (a)Which property of electron is revealed in this observation Ans; wave nature (b)If the electrons are accelerated by a p.d of 55V, what is the value of wavelength associated with electrons Ans;wavelength of electrons= h/ (root of 2meV) where h- planks constant, e- charge of electron ( from last page of clarks table) (c)In similar experiment, if the electron beam is replaced by bullets fired from a gun, no interference pattern is observed. Give reason. Ans;wave length = h/ mv , mass of bullet is very very greater. So wavelength is neglegible. bandwidth =Dxwavelength/d 39.The frequency of incident radiation of a photocell is doubled for the same intensity. What changes will you observe in (a)K.E of photoelectrons emitted? Ans; doubled (b)Photoelectric current flowing through photocell Ans; no change (c)What happens to current conduction if the frequency is below threshold frequency Ans; No current will pass. threshold frequency is the minimum frequency to strt the electron emission. (d)Name two photo cells Ans; Solarcll, Burgler alarm,Fire alarm 40 (b)Define half life period of a radioactive substance Ans; refer text (c)What should be the fission rate of U235 for producing a power of 100W? Given that 200MeV are released per fission of the uranium nucleus 41.Half life of three elements are given in the table. Rank the elements according to their activity Element Half Life 1.Radium 1.6 x 103 Years 2.Lanthanum 1.1 x 1010 Years 3.Phosphourus 14.3 days 42.Radium has a half life of about 1600 years and instantaneous amount of radium is determined using the relation N=Noe-lt. If the universe was formed five billion or more years, why is radium left even now? Ans; after half life period, only half of the radium will reduce. So after billions of years, radium will remain. 43.Classify the following statements as properties of(i) alpha particles and (ii) beta particles (a)They can interact with atoms and as a result they get scattered while traveling through matter. i (b)While coming out from nucleus, they sometimes interact with orbital electrons and thereby eject secondary electrons from electron orbit. i (c)The energy spectrum appears continuous due to the creation of very light particles called neutrino ii d)The velocity and hence kinetic energy of the particles depend on the energy of parent nuclei which emit them ii,i 45.Fission and Fusion process are of nuclear origin (a)Which is more violent explosion-atom boom or hydrogen bomb? Ans; Hydrogen bomb. due to fusion reaction Atom bomb -fission reaction (b)A fusion reaction is more energetic than a fission reaction why? Ans; For fusion reaction very high temperature and pressure is needed. For conducting this, an atom bomb is at the tip of hydrogen bomb. (c)Is fission or fusion process the source of stellar energy Ans; Fusion (d)Explain proton-proton cycle Ans; refer text 46.Condcution of electric current through a semiconductor can be explained using energy band model. (a)Explain the terms valence band and conduction band (b)Using band theory explain the difference between conductors, semiconductors and insulators (c)The forbidden energy gap of germanium is 0.785 eV. What do you mean by this? Ans ; energy gap b/w valance band and conduction band (d)What is the forbidden energy gap of silicon Ans; Gweermanium- .785eV, for silicon-1.21eV 47.If uni-directional property of diode: Rectification, then the break down action of zener diode:will act as a conductor……. 48.Draw the figure of a common emitter transistor in CE configuration with the input forward biased. (a)Identify the transistor as NPN or PNP (b)Complete the above circuit diagram by giving proper bias in the output and connect load resistance of 4kW (c)When the base current changes by 20mA, the change in base emitter voltage is found to be 0.02.V. The observed change in collector is 2mA. What is the voltage gain of the amplifier. (d)npn transistor are preferred in devices with very high frequency source. Why? Ans;In npn transistor,current is mainly carred by electrons. The mobility of electrons is greater than that of holes and ,hence the npn transistor have faster responce and are preffered. 49.A pn junction diode can be used as a rectifier (a)Which characteristic enables a diode to act as a rectifier? Ans; it will conduct only when it is forward biased. (b)A transformer, a diode and a load resistor are given. Design a circuit which enables rectification Ans;Draw half wave rectifier & explain (c)Give the input and output wave form of the above circuit Ans ;draw 50. a)Name the logic gate used as switch Ans; (b)Draw the logic symbol and given the Boolean expression (c)Give the truth table for the above logic gate K.N.HARIHARAPUTHRAN Msc.BEd IMAGINATION RULES THE WORLD PUTHRAN’S Centre for PHYSICS , Behind Govt: Hospital, MANNAR 9656661146 , 9895739984 51.There are 3 types of modulation for a sinusoidal carrier wave (a)What are they Ans;Amplitude modulation,Frequency modulation,Analog madulation (b)What do you understand by the term modulation Ans; define (c)What is the need for modulation Ans;To avoid interference; Many signals travels throuh the same transmission chanals and they interfere each other and it results in distortion.By modulation we can mount the modulating signals on carrer signals of different frequencies by mixing K.N.HARIHARAPUTHRAN Msc.BEd SET Prejudice is the child of ignorance 0479- 2313988,9895739984,9656661146 TERY TO CALL ME AFTER EXAMINATION!!