Q1
mcq
A body acquires charge 8·0 × 10 12 C. The mass of the body :
- A. increases by 4·5 × 10 7 kg
- B. decreases by 1·0 × 10 6 kg
- C. decreases by 4·55 × 10 23 kg
- D. increases by 9·1 × 10 23 kg
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Q2
mcq
A current flows through a cylindrical conductor of radius R. The current density at a point in the conductor is j = r (along its axis), here is a constant and r is distance from the axis of the conductor. The current flowing through the portion of the conductor from r = 0 to r = is proportional to :
- A. R
- B. R2
- C. R3
- D. R4
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Q3
mcq
A particle having charge +q enters a uniform magnetic field as shown in the figure. The particle will describe :
- A. a circular path in XZ plane
- B. a semicircular path in XY plane
- C. a helical path with its axis parallel to Y-axis
- D. a semicircular path in YZ plane
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Q4
mcq
A bar magnet is initially at right angles to a uniform magnetic field. The magnet is rotated till the torque acting on it becomes one-half of its initial value. The angle through which the bar magnet is rotated is :
- A. 30
- B. 45
- C. 60
- D. 75
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Q5
mcq
Which one out of the following materials is not paramagnetic ?
- A. Aluminium
- B. Sodium Chloride
- C. Calcium
- D. Copper Chloride
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Q6
mcq
An ammeter connected in series in an ac circuit reads 10 A. The maximum value of current at any instant in the circuit is :
- A. 10 2 A
- B. A
- C. A
- D. A
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Q7
mcq
The amplitude of electric field in an electromagnetic wave in free space is 1000 Vm 1. The amplitude of the magnetic field in this electromagnetic wave is :
- A. 3·0 × 10 3 T
- B. 3·33 × 10 8 T
- C. 3·0 × 1011 T
- D. 3·33 × 10 6 T
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Q8
mcq
The magnification produced by a spherical mirror is 2·0. The mirror used and the nature of the image formed will be
- A. Convex and virtual
- B. Concave and rea
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Q9
mcq
Choose the correct statement :
- A. Photons of light show diffraction whereas electrons do not show diffraction.
- B. Electrons have momentum whereas photons do not have momentum.
- C. Photons of light and electrons both exhibit dual nature.
- D. All electromagnetic radiations do not have photons.
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Q10
mcq
A beam of red light and a beam of blue light have equal intensities. Which of the following statements is true ?
- A. The blue beam has more number of photons than the red beam.
- B. The red beam has more number of photons than the blue beam.
- C. Wavelength of red light is lesser than wavelength of blue light.
- D. The blue light beam has lesser energy per photon than that in the red light beam.
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Q11
mcq
Which of the following is an electrical conductor at room temperature ?
- A. Sn
- B. Mica
- C. Si
- D. C
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Q12
mcq
A long straight wire is held vertically and carries a steady current in upward direction. The shape of magnetic field lines produced by the current-carrying wire are :
- A. horizontal straight lines directed radially out from the wire.
- B. straight lines parallel to the current-carrying wire.
- C. concentric horizonal circles around the wire.
- D. coaxial helixes around the wire.
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Q13
short answer
Assertion (A) : n-type semiconductor is not negatively charged. Reason (R) : Neutral pentavalent impurity atom doped in intrinsic semiconductor (neutral) donates its fifth unpaired electron to the crystal lattice and becomes a positive donor.
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Q14
short answer
Assertion (A) : A series LCR circuit behaves as a pure resistive circuit at resonance. Reason (R) : At resonance, XL = XC gives = .
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Q15
short answer
Assertion (A) : In double slit experiment if one slit is closed, diffraction pattern due to the other slit will appear on the screen. Reason (R) : For interference, at least two waves are required.
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Q16
short answer
Assertion (A) : For monochromatic incident radiation, the emitted photoelectrons from a given metal have speed ranging from zero to a certain maximum value. Reason (R) : Each metal has a definite work function.
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Q17
long answer
2 marks
(a) In the given figure, three identical bulbs P, Q and S are connected to a battery. (i) Compare the brightness of bulbs P and Q with that of bulb S when key K is closed. (ii) Compare the brightness of the bulbs S and Q when the key K is opened. Justify your answer in both cases.
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Q18
long answer
2 marks
OR (b) Two cells of emf 10 V each, two resistors of 20 and 10 and a bulb B of 10 resistance are connected together as shown in the figure. Find the current that flows through the bulb.
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Q18
short answer
2 marks
Find the angle of diffraction (in degrees) for first secondary maximum of the pattern due to diffraction at a single slit. The width of the slit and wavelength of light used are 0·55 mm and 550 nm, respectively.
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Q19
short answer
2 marks
An equiconvex lens is made of glass of refractive index 1·55. If the focal length of the lens is 15·0 cm, calculate the radius of curvature of its surfaces.
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Q20
short answer
2 marks
Calculate the mass of an alpha-particle in atomic mass unit (u). Given: Mass of a normal helium atom = 4·002603 u; Mass of carbon atom = 1·9926 × 10^-26 kg.
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Q21
short answer
2 marks
A sample of semiconductor has a hole concentration of 8 × 10^8 m^-3. On doping with impurity atoms, the hole concentration becomes 8 × 10^12 m^-3. (a) Identify (i) the type of dopant and (ii) the extrinsic semiconductor so formed. (b) Calculate the electron concentration in the extrinsic semiconductor.
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Q23
long answer
3 marks
(i) Derive an expression for the resistivity of a conductor in terms of number density of free electrons and relaxation time. (ii) The figure shows the plot of current through a cross-section of wire over two different time intervals. Compare the charges (Q1 and Q2) that pass through the cross-section during these time intervals.
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Q23
short answer
3 marks
(a) Write vector form of Biot-Savart law. (b) Two insulated long straight wires, each carrying 2·0 A current are kept along xx and yy axis as shown in the figure. Find the magnitude and direction of resultant magnetic field at point P (4m, 5m).
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Q24
long answer
3 marks
(i) A battery of emf E and internal resistance r is connected to a variable external resistance R. (I) Obtain the expression for current I in the circuit and the value of maximum current the battery can supply. (II) Obtain the terminal voltage V across the battery and its maximum possible value. (ii) The above battery sends a current I1 when R = R1 and a current I2 when R = R2. Obtain the internal resistance of the battery in terms of I1, I2, R1 and R2.
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Q25
short answer
3 marks
(a) State any three characteristics of electromagnetic waves. (b) Briefly explain how and where the displacement current exists during the charging of a capacitor.
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Q26
short answer
3 marks
A double slit set-up was initially placed in a tank filled with water and the interference pattern was obtained using a laser light. When water is replaced by a transparent liquid of refractive index n > n_water, what will be the effect on the following? (a) Speed, frequency and wavelength of the light of laser beam. (b) The fringe width, shape of interference fringes and shift in the position of central maximum.
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Q27
short answer
3 marks
Explain the following observations: (a) Photoelectric emission does not occur from a surface when the frequency of the light incident on it is less than a certain minimum value. (b) It is the frequency, and not the intensity of the incident light which affects the maximum kinetic energy of the photoelectrons. (c) The cut-off voltage (Vo) versus frequency (v) of the incident light curve is a straight line with a slope.
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Q28
short answer
3 marks
(a) What are majority and minority charge carriers of p-type and n-type semiconductors? (b) Explain briefly the formation of diffusion current and drift current in a p-n junction diode.
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A parallel plate capacitor consists of two conducting plates kept generally parallel to each other at a distance. When the capacitor is charged, the charge resides on the inner surfaces of the plates and an electric field is set up between them. Thus, electrostatic energy is stored in the capacitor. parallel and equidistant from each other. The space between P1 and P2and P2 and P3 is completely filled with mica sheets of dielectric constant 2 is connected to point A and other plates P1 and P3 are connected to point B. Point A is maintained at a positive potential with respect to point B and the potential difference between A and B is V.
Q30
mcq
1 mark
The capacitance of the system between A and B will be :
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Q31
long answer
(a) (i) Two point charges + q and q are held at (a, 0) and ( a, 0) in x-y plane. Obtain an expression for the net electric field due to the charges at a point (0, y). Hence, find electric field at a far off point (y >> a). (ii) Three point charges of 2 nC, 1 nC, and + 5 nC are kept at the vertices A, B and C of an equilateral triangle of side 0·2 m. Find the total amount of work done in shifting the charges from A to A1, B to B1 and C to C1.
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Q32
mcq
1 mark
The electric field in the region between P1 and P2 is :
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Q33
mcq
1 mark
The separation between the plates of same area (L2) of a parallel plate air capacitor having capacitance equal to that of this system, will be :
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Q34
mcq
1 mark
If the source of potential difference applied between A and B is removed, and then A and B are connected by a conducting wire, the net charge on the system will be :
- D. Zero
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A hydrogen atom consists of an electron revolving in a circular orbit of radius r with certain velocity v around a proton located at the nucleus of the atom. The electrostatic force of attraction between the revolving electron and the proton provides the requisite centripetal force to keep it certain stable orbits. The angular momentum of the electron in these orbits is some integral multiple of Further, when an electron makes a transition from one orbit of higher energy to that of lower energy, a photon is emitted having energy equal to the difference between energies of the initial and final states. Assuming the mass and charge of an electron as m and e respectively, answer the following questions.
Q35
mcq
1 mark
The expression for the speed of electron v in terms of radius of the orbit (r) and physical constant (K = ) is :
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Q36
mcq
1 mark
The total energy of the atom in terms of r and physical constant K is :
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Q37
mcq
1 mark
A photon of wavelength 500 nm is emitted when an electron makes a transition from one state to the other state in an atom. The change in the total energy of the electron and change in its kinetic
- A. 2·48, 2·48
- B. 1·24, 1·24
- C. 2·48, 2·48
- D. 1·24, 1·24
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Q38
mcq
1 mark
The speed of electron in its nth orbit is proportional to :
- A. n
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Q39
mcq
1 mark
An electron makes a transition from 3·4 eV state to the ground state in hydrogen atom. Its radius of orbit changes by : (radius of orbit of electron in ground state = 0·53 Å)
- A. 0·53 Å
- B. 1·06 Å
- C. 1·59 Å
- D. 2·12 Å
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Q41
long answer
5 marks
Two point charges +q and -q are held at (a, 0) and (-a, 0) in x-y plane. Obtain an expression for the net electric field due to the charges at a point (0, y). Hence, find electric field at a far off point (y >> a).
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Q42
long answer
5 marks
Three point charges of 2 nC, 1 nC, and + 5 nC are kept at the vertices A, B and C of an equilateral triangle of side 0.2 m. Find the total amount of work done in shifting the charges from A to A1, B to B1 and C to C1. Here A1, B1 and C1 are the midpoints of sides AB, BC and CA, respectively.
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Q43
long answer
5 marks
State Gauss's law. Using it, derive an expression for the electric field due to a uniformly charged thin spherical shell of radius r at a point at a distance y from the centre of the shell such that (I) y > r, and (II) y < r.
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Q44
long answer
5 marks
A point charge of + 2 nC is kept at the origin of a three-dimensional coordinate system. Find the type and magnitude of the charge which should be kept at (0, 0, 6m) so that the potential due to the system becomes zero at (0, 0, 2m).
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Q45
long answer
5 marks
Define motional emf. Derive an expression for motional emf by using the principle of conservation of energy.
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Q46
long answer
5 marks
A square shaped loop of side l is initially lying outside a region of uniform magnetic field as shown in the figure. The loop is moved towards right with a constant velocity v till it goes out of the region of magnetic field. (I) What will be the directions of induced current when the loop enters the field and when it leaves the field ? (II) Draw the plots showing the variation of magnetic flux Φ linked with the loop with time t and variation of induced emf E with time t. Mark the relevant values of E, Φ and t on the graphs.
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Q47
long answer
5 marks
Differentiate between peak and rms values of alternating current. How are they related?
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Q48
long answer
5 marks
A current element X is connected across an ac source of emf V = V0 sin 2πνt. It is found that the voltage leads the current in phase by π/2 radian. If element X was replaced by element Y, the voltage lags behind the current in phase by π/2 radian. (I) Identify elements X and Y by drawing phasor diagrams. (II) Obtain the condition of resonance when both elements X and Y are connected in series to the source and obtain expression for resonant frequency. What is the impedance value in this case?
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Q49
long answer
5 marks
An object is placed 30 cm from a thin convex lens of focal length 10 cm. The lens forms a sharp image on a screen. If a thin concave lens is placed in contact with the convex lens, the sharp image on the screen is formed when the screen is moved by 45 cm from its initial position. Calculate the focal length of the concave lens.
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Q50
long answer
5 marks
Calculate the angle of minimum deviation of an equilateral prism. The refractive index of the prism is √3. Calculate the angle of incidence for this case of minimum deviation also.
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Q51
long answer
5 marks
A physics teacher wants to demonstrate interference with the help of double slit experiment using a laser beam of 633 nm wavelength. Since the hall is large enough, interference pattern is formed on the wall 5.0 m from the slits. For clear and comfortable view by all the students they want the fringe width 5 mm. (I) Find the slit separation for obtaining the desired interference pattern. (II) How far will the first minimum be from the central maximum?
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Q52
long answer
5 marks
A parallel beam of light of wavelength 650 nm passes through a slit of width 0.6 mm. The diffraction pattern is obtained on a screen kept 60 cm away from the slit. Find the distance between first order minima on both sides of the central maximum.
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