Class 12 AHSEC 2022 Physics Question Paper Solved English Medium

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Class 12 AHSEC 2022 Physics Question Paper Solved English Medium

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PHYSICS

2022

PHYSICS OLD QUESTION PAPER SOLVED

1. Answer any eight questions from the following as directed:

(a) How many electrons are there in a body if its total charge is 16×10^-18 C?

Ans: n = 100.

(b) Which of the options expresses Wheatstone bridge principle as given in your textbook?

(i) R₁/R_2.= R₃/R₄; when i_g = 0

(ii)R₁/R/₃= R₂/R₄; wheni_g = 0

(iii) Both of the above express the principle.

(iv) None of the above expresses the principle (choose the correct options)

Ans: R₁/R₂= R₃/R₄; when i_g=0

(c) Which of gsuss and Tesla is a bigger unit? Write the radio of 1 Gauss to 1 Tesla.

Ans: T>G,1G/1T=10^-4.

(d) Fill up the blanks in the expression Wb=___m²

Ans: Wb =___m²

(e) Which of the following options is correct?

(i) c²= 1/u₀e₀= E₀²/B₀²

(ii) c²= 1/u₀e₀= B₀²/E₀²

(iii) Both the above options are correct.

(iv) None of the above.

Ans: c²= 1/u₀e₀= E₀²/B₀²

(f) What is the angle between reflected and refracted rays when Brewster’s law is a applicable?

Ans: 90°.

(g) In a prism except the position of minimum deviation there are__ valuse of angle of incidence producing same angle of deviation.(Fill in the blanks)

Ans: two

(h) de broglie in 1924 reasoned that nature was symmetrical and that the two basic physical entities __ and ___ must have symmetrical character.

Ans: matter & energy.

(I) According to Bohr’s second postulate of quantisation, the angular momentum of electron in the first possible orbit is -(Choose the correct option)

(i) 2π/h (ii) h/2π (iii) 2π/h (iv) h2π

Ans: h/2π.

(j) Which of the following options is a correct unit of a diode’s reverse current?

(i)A (ii) mA (iii) uA (iv) None of the above. (Choose the correct option)

Ans: uA.

(K) The act of transmission of information is ___ .(Fill in the blanks)

Ans: Communication.

(l) H₂o is a polar/non- polar molecule.(Choose the correct word)

Ans: H₂o is a polar.

2. Answer the questions/Fill in the blanks from the following:(any ten)

(a) (i) Draw the field lines between two charges+Q₁and -Q₂, when another charge+Q is placed between them in a straight line.

Ans:

(ii) Calculate the electrical froce between two 1C charges placed 100cm apart, Given e₀= 8.854×10^-12c²N^-1m^-2.Mention two smaller units of c.

Ans: F= 9×10⁹×1×1/1²=9×10⁹N.

(b) (i) Are the following diagrams equivalent? If yes or no, calculate the equivalent resistance between the points A and B in the figure (ii) when the mid -point of the resistances are conected by a conducting wire.

Ans:

(ii) What will be the total charge q in a conductor having length L, diameter D and electron n respectively?

Ans: v = πD²/4L = n = q/v = q = _πd²/4L(n).

(C) (i) Explain why a potentiometer is suitable than a voltmeter for measuring emf of a cell.

Ans: It is a device which is used to measure potential difference.Because it dose not draw any current from the source of emf at the null point.

(ii) A 10m long potentiometer wire has a resistance of 18 ohm. If the two ends of it are connected to a battery of 5volt, calculate the potential drop per unit length with unit. Given, internal resistance of the battery is 2Ω.

Ans: Here balancing lenght is

(d) (i) Static charges produce __ field while moving charges produce ___ field.

Ans: Electric field, Magnetic field.

(ii) Write the analogous equation is. Electricity if in magnetism it is expressed τ=m×B and mention the unit of m.

Ans: τ=P×E=m=Am²

(e) (i) Can a changing magnetic field exert froce on a stationary charge? Also can a moving charge exert froce/troque on a stationary magnet? Try to give your answer by a brife statement of your own.

Ans: A changing magnetic field exert froce on a stationary charge because it induces ele ctric field. Also a moving charge exert/torque on a stationary magnet: because a moving charge is equivalent to current and current produces the magnetic field and that exert froce on other magnet.

(ii) In a rainy season you are running with your umbrella opened in a place where the horizontal component of Earth’s magnetic field is 0.26G.If the length of your umbrella is 80cm and your speed is 20km/hr, calculate the motivation emf developed across its shaft.

Ans: B=.26×10^-4(T);l=8m

V=20k|m|h; V= 20×5/18 m/s

E=B×L×V=.26×10^-4×.8×20×5/18.

(f) (i) A plane electromagnetic wave is propagating in space along x-axis. If the magnetic field component of the wave is as given below, write an expression for its electric field. B_y= 2×10^-7sin (kx-ωt)

Ans: E₀₌B_0.c;E₀/B₀=C.=E₀=2×10^-7×3×10⁸=60

E_z=E₀Sin(K_x-W_t)=60 sin(K_x– W_t).

(ii) __ layer in the atmosphere plays a protective role,and hence it’s depletion by__ gas is a matter of international concern.

Ans: Ozone, CFC.

(g) (i) Rays parallel to each other but not parallel of the principal axis of a con cave mirror will meet reflection at the __ . Draw a diagram in support of your answer:

Ans: focal plane,

(ii) Write two conditions for a ray to suffer total internal reflection.

Ans: (a) i>C, (b) Incident ray should travel in optically danger medium.

(h) (i) How many processes are there to produce induced emf or current as mentioned in your textbook? If an area A is placed in a magnetic field B so that the normal to the area makes 45° with the megnetic field , what will be the flux throught the area?

Ans: Three process are there to produce induced emf or current as mentioned in text book .Q=BA CosQ.

(ii) State Lenz’s law. Name the other law of nature that it obeys.

Ans: If a magnet is moved towards or away from the coil, an induced current is produced in the circuit. According to Lenz’s law, this curre opposes the cause that is the motion of the magnet. Hence work is to be done to move the magnet against this force. It is this work which is transformed into the electrical energy of the induced current. Thus the electrical energy is obtained at the cost of mechanical energy spent.

Hence, Lenz’s law is in conformity with the law of conservation of energy.

Lenz’s law obeys the law of conservation of energy and newton’s third law.

(I) (i) Write the mathematical expression of the postulate that an electron has to strictly follow in order to revolve round the nucleus.Name the scientist who proposed it in 1913.

Ans: L=nh/2π; Neil Bohr proposed it in 1913.

(ii) Calculate the energy in joule that is equivalent to 1MeV.

Ans: 1Mev=1×10⁶×1.6×10^-19J.

(j) (i) The total energy of an electron in the first orbit is -13.6 eV. Does it mean that-

(a) the electron is bound with the nucleus?

Ans: Yes.

(b) energy will be required to remove the electron to infinity?

Ans: +13.6 ev.

(k)(i) The transistor works as an amplifier, with its emitter-base junction__biased. In this state the transistor is said to be in__ state.

Ans: Forward; Reverse; Active.

(ii) What are logic gates? Draw the symbol and write the truth table of a NOT gate.

Ans: Logic Gates are the basic building blocks of digital electronics. It is a digital circuit which follows logical relationship between input and Output.

Symbol:——-(NOT GATE) truth table:

(l) (i) What do you understand by the terms signal and noise in communication system?

Ans: Signal: Information in electrical form Suitable for transmision.

Noise: Unwanted signal disturb transmision.

(ii) The approximate bandwidth required to transmit___ is 20kHz and to transmit___is 4.2 MHz.

Ans: music, video signal.

3.(a) (i) Show that in a particular way of combination of capacitors the equivalent capacitance C is expressed as given below and name the particular combination.C ₁+c₂+c+₃+…….+c_n

Ans: In Parallel Commission,the total capacitor C is C ₁+c₂+c+₃+…….+c_n

Where , C ₁+c₂+c+₃+…….+c_nare individual capacitances.

The General formula for effective capacitance C for parallel commission of n Capacitors follows₁+c₂+c+₃+…….+c_n.

(ii) Mention at least two factors on which capacity of a capacitor does depend. Define the unit of capacitance. Find out the dimensions of capacitance using the dimensions of charge and potential difference.

Ans: (i) Geometrical Configuration.

(ii) Nature of insulating between conductors.

(Unit of Capacitane) farad.

Dimension →M^–¹L^–²T⁴A²

C = Q/V = Q/W/Q = Q²/W =

A²T²/ML²T^-2.M^-1,L^-2,T⁴A².

(b) (i) Show that current in each resistor of the following diagram is zero.

Ans: When potential difference is same current can’t flow.

(ii) What do you mean by mobility of mobile charges? Whether it is positive or negative. Show that mobility is expressed as given below, where the symbols have their usual meaning. U= eπ/m

Ans: The mobility of a charge carrier is defined as the drift velocity of the charge carrier per unit electric field.

(c) (i) Ej and Bk are electric and magnetic fields respectively placed in a region. A charge q is moving with velocity vi into the region.

show that v = E/B. Name the arrangement of E and B fields.

(iii) What is a galvanometer? A galvanometer has a resistance of 50Ω. If across its terminals resistance of 5Ω is connected,calculate the fraction of current that flows through the galvanometer.

Ans: Galvanometer is a device to detect the small current.

50i_g= 5(i – i_g) =10=i / i_g-1⇒11= i / i_g⇒i_g / i = 1/11.

(d) (1) What is mutual inductance? S₁ and S₂are two long coaxial solenoids of radii r₁and r₂where r₁<<r₂. S₁ and S₂ have equal lengths /. If n₁and n₂ be the number of turns/length and I₁be the current flowing through S₂, find an expression for mutual inductance M₁₂of S₁ with respect to S₂.

Ans: Mutual inductane is where the magnetic field generated by a coil of wire induces voltage in an coil of wire. where a current I₁flow through the outer circular coil. The field at the centre of the coil’s B₂ = μ₀l₂ / 2r₂. Since the other co-axially placed coil has a very smal radius, B₂ may be considered constant, overits cross-sectional areas,

Hence,

(ii) Two concentric coils having radii r₁ and r₂are placed coaxially, where r₁<<r₂ obtain an expression for mutual inductance M₁₂of the inner coil with respect to the outer coil. Define self-inductance.

Ans: N₁ = no. of turns per unit length of inner coil

N₂ = no. of turns per unit length of outer coil

R₁= and r, radius

L = length of coil (both)

L₁= current flowing in inner coil

Magnetic field B due to this current

Bis only inside coil 1

Outside coil IB=0

Magnetic flux through I turn of coil 2 due to B is = Bx Area = μ₀ n₁i₁

Total no. of turns in coil 2⁼n₂^×L

Mutual inductance M is = M^×i

So, M=μ0n₁n₂zr₂L

Self-inductance is the tendency of a coil to resist changes in current in itself. Whenever current changes through a coil, they induce an EMF, which is proportional to the rate of change of current through the coil. Created by Mahesh

Shenoy.

(e) (i) Arrange the following words, so that it becomes a meaningful sentence. “A parallel plate capacitor of very low frequency cannot pass through an alternating current.” Write in brief about the need of displacement current.

Ans: Low Frequency AC Can’t pass through parallel plate capacitor.

(a) Makes’Ampare- Maxwell law more consistant.

(b) Shows the symmetry of laws of electricity and mequetism.

(ii) Write M (Microwaves), U (Ultraviolets), R(Radio waves), V (Visible waves), X(X-rays), I(infrared waves) and G(Gamma rays) in the order of decreasing frequency.

Ans: G>X>U>V>I>R.

Give a short description of any one of the following:

(a) Sky waves

Ans: Sky waves: Sky wave refers to the propagation of Ratio waves reflected or refracted back toward Earth from the ionosphare an electrically charged layer of the upper atmosphere.

(b) Space waves

Ans: Space waves: The component of an electromagnetic wave that travels directly from transmitter to receiver without being reflected.

(f) (i) A beam of light converges at a point P. If a lens is placed in the path of convergent beam at a distance of 12cm from P, at what point does the beam converge if the lens is a convex lens of focal length 20cm? Draw a neat diagram of it.

Ans: U-12 C: M

1/v- 1/u = 1/f ⇒1/v -1/12 = 1/20 ⇒1/v = 1/20+1/12⇒1/v = 3 + 5/60

V= 60/8=7.5 C.M.

(ii) State superposition principle of waves. Mention at least one example of coherent source of light. What will be the phase difference between two light waves, if the path difference between them is 2.5A?

Ans: When two or more waves overlap in space, the resultant disturbance is equal to the algebric sum of the individual disturbances. Laser Light is an example of coherent source of light.

π → 2π

2.5π → 5π

(g) (i) The kinetic energy of an electron is 120eV. Calculate its momentum and speed.

Ans: P = √2mE_k

⇒P = √2m×120

∴ P= MV.

⇒√2m×120= MV

⇒√2m×120= M²V

⇒240= MV.

P= MV

⇒240 = P

∴(240)²= 2M×120

⇒240×240²= 2M×120

⇒240=M

(ii) Write a few lines on any one of the following:

(a) Wave nature of matter

Ans: A particle of Man (m),moving with velocity (v) could behave like a wave under suitable condition. And the corresponding wave related to that matter is called matter wave.

(b) Davisson and Germer experiment (no need to draw diagram).

Ans: Davission and Germer experiment- The Davisson – GERNER Experiment was a 1923-27 experiment by clinton Davisson and Lester Germer at western Electric in which electrons, scattered by the surface of a crystel of nickel metal, displayed a differection pattern.

(h) (i) Name the formula given below. Using the value 1.097×10^-7m¹, if needed, find the wavelength of H_aline. Arrange H_a H_band H_A line in the spectrum of hydrogen in the order of decreasing wavelength.1/A=R(1/2²-1/n²) 1/2+2+1/2=3

Ans: Dalmer Formula: 1/λ = R (1/2²-1/n²) = the value of R=1.97×10^7m-1

1/λ=1.097×10⁷(1/2²-1/3²)m^-1= 1.522×10⁶m^-1∴λ = 656.3nm

H∝> H_B>H⋎

(ii) Name the processes of the following nuclear reactions:

(i) (i) Draw a neat and labelled diagram of a full-wave rectifier indicating the primary and secondary of the centre tap transformer, two junction diodes, one load resistance and a capacitor for filtration of ripples. Moreove the wave patterns after passing through each diode and also through the load resistor.

Ans: A device or a circuit which rectifies both halves of each cycle of an alternating voltage is called a full-wave rectifier.

Electric circuit: The alternating voltage to be rectified is applied across the primary coil (P₁P₂) of a transformer with a center-tapped secondary coil (S₁S₂). The terminals S₁ and S₂ of the secondary are connected to the two p-regions of two junction diodes D₁ and D₂ respectively. The center-tap Tis connected to the ground. The load resistance RL is connected across the common n-regions and the ground.

Full-wave rectifier circuit

P₁P_2,S₁S₂-Primary and secondary transformer,

T-Centre -tap on secondary,

D₁D₂-Junction diodes,

R_L-Load resistance,

I_L-load current,

V_i-AC input voltage,

V-Dc output voltage,

Working: During the one-half cycle of the input, terminal S₁ of the secondary is positive while S₂ is negative with respect to the ground (the centre-tap T). During this half cycle, diode D₁is forward biased and conducts, while diode D₂ is reverse basid and does not conduct.The direction of current l_L through R_L is in the sense shown.

Voltage waveforms for a full-wave rectifier

(a) input (b) output

During the next half-cycle of the input voltage, S₂ becomes positive while S, is negative with respect to T. Diode D₂ now conducts sending a IL through R_L in the same sense as before. D₁ now does not conduct. Thus, the current through R_L flows in the same direction, i.e., it is unidirectional, for both halves or the full wave of the input. This is called full-wave rectification. The output voltage has a fixed polarity but varies periodically with the time between zero and a maximum value. The above figure shows the input and output voltage waveforms, The pulsating de output voltage of a full-wave rectifier has twice the frequency of the input.

(ii) Describe any one optoelectronic junction device mentioned in your textbook.

Ans: Photodiodes. solar cells are the examples of optoelectronic function device mentioned in textbook.

4. (a) (i) What is an ac generator? A coil of area A, number of turns N is rotating

in a magnetic field B with steady angular speed ω. Show that the system generates alternating current or emf at any time t. Draw a graph of ε vs t. Name three types of such generators.

Ans: AC Generator converts the mechanical energy into electrical energy. From Faraday’s law the induced Emf for the rotating coil of N turns,

Then, ε =- N dob/dt = -NBA d/dt (coswt)

Thus the instantaneons value of emf is ε = NBAω sinωt. Here, NBAw is the maximum value of the emf, which occurs when sinωt=±1. Since the value of sine function varies between +1 & -1 the sign or polarity of the emf changing with time.

(i) Hydro electric, (ii) Thermal (iii) Nuclear power.

(ii) Define rms value of ac. Show that the ratio of rms value of ac to its peak value is 0.707. An electric bulb which operates at 12V de is connected to an ac source and glows normally, what would be the peak value of the source?

Ans: rms current is the equivalent DC current that would produce the same average power loss as AC.

Ims = i₀(ii) Define rms value of ac. Show that the ratio of rms value of ac to its peak value is 0.707. An electric bulb which operates at 12V de is connected to an ac source and glows normally, what would be the peak value of the source?

Ans: rms current is the equivalent DC current that would produce the same average power loss as AC.

ims = i₀√2=.707i₀

V_dc=Vrms=12V

V = 12√2volt.

(iii) Discuss ac voltage connected to a resistor (R). When an inductor (L) and a capacitor (C) are connected to ac voltage separately then the currents in both the cases are expressed as given below. Write a few lines on each of the following.

i=i_m sin(ωt-π/2)

i=i_m sin(ωt+π/2)

Ans:

(b) (i) Find out an expression for fringe width in Young’s double slit experiment. screen is placed at a distance of 1m from the slits, calculate the fringe width of Light of wavelength 500nm is incident on two slits which are 1mm apart. If the the fringe pattern formed on the screen.

Ans: B=XD/d = 500×10^-9×1m./10^-3m

Considering a point p at a distance x from c.The path difference between two waves arriving at p.

(ii) When the double slit in Young’s experiment is replaced by a single slit, name the pattern of fringes formed on the screen. What is the phenomenon due to which we see colours when a CD is viewed? Mention at least one difference in the fringe pattern observed due to interference and diffraction phenomena. Describe a simple experiment by which you can observe the diffraction phenomenon in your home.

Ans: Diffraction pattern In CD colour results due to phenomenon of diffraction in which small ripples on the surface of it breakup white light into the colour of rainbow. The width of the fringes in case of diffraction is not equal white of fringe width in case of interfence is equal. One can easily demonstrate diffraction using a candle or a small bright flashlight bulb and a shift made with two pencils.

(iii) What do you mean by polarisation of light? Name the law which gives us the intensity of emergent light when passes through a polariser at different angles. Mention two ways of observing polarisation as described in your textbook. State Brewster’s law. Find out the Brewster angle when there is transition of light from air to glass.

(Hints: tan 1.5= 0.026, sin 1.5=0.026,cos1.5=0.99, tan^-11.5≈56)

Ans: Polarisation of light – The process of transforming unpolarized light waves to a polarized light waves is called polarised of light.

Malus Law.

Scatering & Reflection.

μ = tanip

ip = tan^–¹ μ = tan ^–¹(1.5) = 56

(c) (i) Write an expression for mass defect using ΔM,Z,m_p,A,m_n and M where the symbols have their usual meaning. Define binding energy of a nucleus.Obtain the binding energy in Me V of a nitrogen nucleus. Given,

m(14/4N) = 14.00307u

m_{H =}1.007825u

m_n= 1.008665u

I_u=931.5MeV/c²

Ans: ΔM=Zmp+(A-Z) mn-M

Binding Energy, amount of energy required to separate a particle from a system of particles or to disperse all the particles of the system.

IU=1.6605×10^-27kg.

Equivalent Energy= 1.6605×10^-27x(2.9979×10⁸)²kgm^2/s²

=1.4924×10^-10j.=1.4924×10^-10/1.602×10^-19 ev=931.5 Mev or IU=931.5Mev/c²

For 14/7 N=14.00307×931.5=13,044.

(iii) Draw a schematic labelled diagram of a nuclear reactor based on thermal neutron fission. What is a moderator? Give two examples of moderator. Write a few lines on controlled thermonuclear fission.

Ans:

Systematic diagram of a nuclear reactor based on thermal newtron fussion. Moderators slows the speed of the neutrons. It is also known as a neutron Moderators. Thermo nuclear reaction, fusion of two light atomic nuclei into a single heavier nucleus by a collision of the two interacting particles at extremly high temperature, with the consequent release of a relatively large amount of energy.

(iii) You are given two circuits consisting NAND gates as shown below. Fill up the truth table for each. Are NOR gates considered as universal? If Yes or No, answer why.