Q1
mcq
1 mark
An electric dipole of dipole moment 1·0 × 10 12 Cm lies along x-axis. An electric field of magnitude 2·0 × 104 NC 1 is switched on at an instant in the region. The unit vector along the electric field is + . The magnitude of the torque acting on the dipole at that instant is :
- A. 0·5 × 10 6 Nm
- B. 1·0 × 10 8 Nm
- C. 2·0 × 10 8 Nm
- D. 4·0 × 10 8 Nm
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Q2
mcq
1 mark
When the switch of the circuit is turned on, the filament of the bulb glows instantaneously because :
- A. the electrons coming from the power source move fast through the initially empty filament.
- B. the filament may be old having low resistance.
- C. electric field is established instantaneously across the filament which pushes the electrons.
- D. free electrons in the filament travel with the speed of light.
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Q3
mcq
1 mark
A particle with charge q moving with velocity = v0 enters a region with magnetic field = B1 + B2. The magnitude of force experienced by the particle is :
- A. qv0 (B1 + B2)
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Q4
mcq
1 mark
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
1 mark
The materials having negative magnetic susceptibility are :
- A. diamagnetic
- B. paramagnetic
- C. ferromagnetic
- D. non-magnetic
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Q6
mcq
1 mark
When current in a coil changes at a steady rate from 8 A to 6 A in 4 ms, an emf of 1 5 V is induced in it. The value of self-inductance of the coil is :
- A. 6 mH
- B. 12 mH
- C. 3 mH
- D. 9 mH
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Q7
mcq
The electric field in space between the plates of a parallel plate capacitor (each of area 2·5 × 10 3 m2) is changing at the rate of 4 106 Vm1s1. The displacement current between the plates of the capacitor is :
- A. 1·8 × 10 5 A
- B. 3·47 × 10 6 A
- C. 8·85 × 10 8 A
- D. 6·32 × 10 4 A
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Q8
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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Q9
mcq
1 mark
Which of the following is a semiconductor?
- A. Sn
- B. Mica
- C. Si
- D. C
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Q9
mcq
Which of the following is an electrical conductor at room temperature ?
- A. Sn
- B. Mica
- C. Si
- D. C
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Q10
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 real
- C. Concave and virtual
- D. Convex and real
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Q11
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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Q12
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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Q13
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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Q14
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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Q15
short answer
Assertion (A) : A series LCR circuit behaves as a pure resistive circuit at resonance. Reason (R) : At resonance, XL = XC gives ω = 1/√(LC).
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Q16
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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Q17
short answer
2 marks
Intrinsic semiconductor has a carrier 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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Q18
short answer
2 marks
In a double slit experiment, the two slits are 1.5 mm apart. The slits are illuminated by a mixture of lights of wavelengths of 600 nm and 400 nm and the interference pattern is observed on a screen 1.5 m away from the slits. Find the minimum distance of the point from the central maximum at which bright fringes of the interference patterns of the two wavelengths coincide.
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Q19
short answer
2 marks
Find the focal length of plano-convex lens of refractive index 1.5 and radius of curvature 10 cm when it is immersed in a liquid of refractive index 1.25.
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Q20
short answer
2 marks
Find the ratio of minimum to maximum wavelength of radiations emitted when electron jumps from higher energy state into ground state of hydrogen atom.
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Q22
short 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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Q22
short answer
3 marks
(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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Q23
short answer
2 marks
(b) Two cells of emf 10 V each, two resistors of 20 ohm and 10 ohm and a bulb B of 10 ohm resistance are connected together as shown in the figure. Find the current that flows through the bulb.
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Q23
short answer
3 marks
(a) A charged particle q moving with a velocity is subjected to a uniform magnetic field acting perpendicular to it. If a uniform electric field is also set up in the region along the direction of velocity, describe the path followed by the particle and draw its shape. (b) How will the magnetic field inside a long solenoid be affected when : (i) the radius of the turns of the solenoid is increased, (ii) the length of solenoid as well as the total number of its turns are doubled ?
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Q24
short answer
3 marks
(a) Differentiate between magnetic flux through an area and magnetic field at a point. (b) A bar magnet is held with its length along the axis of a closed coil. Initially the south pole of the magnet faces the coil. If the magnet is moved towards the coil, explain how a current is induced in the coil and in what direction.
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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) Draw the shape of the refracted wavefront from a convex lens. (b) A plane wave travelling in a medium is incident on a plane surface separating this medium from a rarer medium. Draw a diagram to show the refracted wavefront.
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Q27
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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Q30
short answer
3 marks
(a) (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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Q31
short answer
3 marks
(b) (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.
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Q32
long answer
3 marks
Explain how and where the displacement current exists during the charging of a capacitor. (a) Define wavefront. Draw the shape of the refracted wavefront from a convex lens.
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Q33
long answer
3 marks
A plane wave travelling in a medium is incident on a plane surface separating this medium from a rarer medium. Draw a diagram.
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Q34
long answer
3 marks
What are majority and minority charge carriers of p-type and n-type semiconductors?
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Q35
long answer
3 marks
Explain briefly the formation of diffusion current and drift current in a p-n junction diode.
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Q36
long answer
3 marks
Derive an expression for the resistivity of a conductor in terms of number density of free electrons and relaxation time.
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Q37
long answer
3 marks
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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Q38
long answer
3 marks
(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.
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Q39
long answer
3 marks
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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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 h/2π. 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.
Q40
mcq
1 mark
The expression for the speed of electron v in terms of radius of the orbit (r) and physical constant (K = 1/4πε₀) is :
- A. Not provided
- B. Not provided
- C. Not provided
- D. Not provided
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Q41
mcq
1 mark
The total energy of the atom in terms of r and physical constant K is :
- A. Not provided
- B. Not provided
- C. Not provided
- D. Not provided
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Q42
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 energy are respectively :
- A. 2·48 eV, 2·48 eV
- B. 1·24 eV, 1·24 eV
- C. 2·48 eV, 2·48 eV
- D. 1·24 eV, 1·24 eV
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Q43
mcq
1 mark
The speed of electron in its nth orbit is proportional to :
- A. n
- B. 1/n
- C. n²
- D. 1/n²
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Q44
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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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. The space between P1 and P2 and P2 and P3 is completely filled with mica sheets of dielectric constant 2. Plate P2 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.
Q45
mcq
1 mark
The capacitance of the system between A and B will be :
- A. Not provided
- B. Not provided
- C. Not provided
- D. Not provided
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Q46
mcq
1 mark
The charge on plate P1 is :
- A. Not provided
- B. Not provided
- C. Not provided
- D. Not provided
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Q47
mcq
1 mark
The electric field in the region between P1 and P2 is :
- A. Not provided
- B. Not provided
- C. Not provided
- D. Not provided
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Q48
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 :
- A. Not provided
- B. Not provided
- C. Not provided
- D. Not provided
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Q49
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 :
- A. Not provided
- B. Not provided
- C. Not provided
- D. Not provided
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Q50
long answer
5 marks
Differentiate between peak and rms values of alternating current. How are they related ?
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Q51
long answer
5 marks
A current element X is connected across an ac source of emf V = V0 sin 2 vt. It is found that the voltage leads the current in phase by pi/2 radian. If element X was replaced by element Y, the voltage lags behind the current in phase by pi/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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Q52
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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Q53
long answer
5 marks
Calculate the angle of minimum deviation of an equilateral prism. The refractive index of the prism is sqrt(3). Calculate the angle of incidence for this case of minimum deviation also.
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Q54
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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Q55
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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Q56
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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Q57
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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Q58
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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Q59
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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