Q1
mcq
1 mark
A thin plastic rod is bent into a circular ring of radius R. It is uniformly charged with charge density. The magnitude of the electric field at its centre is :
- A. 2 R0
- B. Zero
- C. 0R
- D. 40R
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Q2
mcq
1 mark
Ten capacitors, each of capacitance 1 µF, are connected in parallel to a source of 100 V. The total energy stored in the system is equal to :
- A. 10 2 J
- B. 10 3 J
- C. 0·5 10 3 J
- D. 5·0 10 2 J
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Q3
mcq
1 mark
Consider the circuit shown in the figure. The potential difference between points A and B is :
- A. 6 V
- B. 8 V
- C. 9 V
- D. 12 V
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Q4
mcq
1 mark
A loop carrying a current I clockwise is placed in x y plane, in a uniform magnetic field directed along z-axis. The tendency of the loop will be to :
- A. move along x-axis
- B. move along y-axis
- C. shrink
- D. expand
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Q5
mcq
A 10 cm long wire lies along y-axis. It carries a current of 1.0 A in positive y-direction. A magnetic field B = (5 mT)j + (8 mT)k exists in the region. The force on the wire is :
- A. (0·8 mN)i
- B. (0·8 mN)i
- C. (80 mN)i
- D. (80 mN)i
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Q6
mcq
A galvanometer of resistance G is converted into an ammeter of range 0 to I A. If the current through the galvanometer is 0.1% of I A, the resistance of the ammeter is :
- A. G/999
- B. G/1000
- C. G/1001
- D. G/100·1
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Q7
mcq
The reactance of a capacitor of capacitance C connected to an ac source of frequency n is X. If the capacitance of the capacitor is doubled and the frequency of the source is tripled, the reactance will become :
- A. X/6
- B. 6X
- C. X/3
- D. X/2
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Q8
mcq
In the four regions, I, II, III and IV, the electric fields are described as : Region I : Ex = E0 sin (kz - wt) Region II : Ex = E0 Region III : Ex = E0 sin kz Region IV : Ex = E0 cos kz The displacement current will exist in the region :
- A. I
- B. IV
- C. II
- D. III
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Q9
mcq
The transition of electron that gives rise to the formation of the second spectral line of the Balmer series in the spectrum of hydrogen atom corresponds to :
- A. nf = 2 and ni = 3
- B. nf = 3 and ni = 4
- C. nf = 2 and ni = 4
- D. nf = 2 and ni = 5
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Q10
mcq
Ge is doped with As. Due to doping,
- A. the structure of Ge lattice is distorted.
- B. the number of conduction electrons increases.
- C. the number of holes increases.
- D. the number of conduction electrons decreases.
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Q11
mcq
Two beams, A and B whose photon energies are 3·3 eV and 11·3 eV respectively, illuminate a metallic surface (work function 2·3eV) successively. The ratio of maximum speed of electrons emitted due to beam A to that due to beam B is :
- A. 3
- B. 9
- C. 1/3
- D. 1/9
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Q12
mcq
The waves associated with a moving electron and a moving proton have the same wavelength. It implies that they have the same :
- A. momentum
- B. angular momentum
- C. speed
- D. energy
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Q13
short answer
Assertion (A) : In photoelectric effect, the kinetic energy of the emitted photoelectrons increases with increase in the intensity of the incident light. Reason (R) : Photoelectric current depends on the wavelength of the incident light.
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Q14
short answer
Assertion (A) : The mutual inductance between two coils is maximum when the coils are wound on each other. Reason (R) : The flux linkage between two coils is maximum when they are wound on each other.
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Q15
short answer
Assertion (A) : Two long parallel wires, freely suspended and connected in series to a battery, move apart. Reason (R) : Two wires carrying current in opposite directions repel each other.
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Q16
short answer
Assertion (A) : Plane and convex mirrors cannot produce real images under any circumstance. Reason (R) : A virtual image cannot serve as an object to produce a real image.
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Q17
short answer
2 marks
Find the temperature at which the resistance of a wire made of silver will be twice its resistance at 20 C. Take 20C as the reference temperature and temperature coefficient of resistance of silver at 20 C = 4·0 10 3 K -1.
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Q18
short answer
2 marks
Monochromatic light of frequency 5·0 1014 Hz passes from air into a medium of refractive index 1·5. Find the wavelength of the light (i) reflected, and (ii) refracted at the interface of the two media.
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Q19
short answer
2 marks
A plano-convex lens of focal length 16 cm is made of a material of refractive index 1.4. Calculate the radius of the curved surface of the lens.
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Q19
short answer
2 marks
An object is placed 30 cm in front of a concave mirror of radius of curvature 40 cm. Find the (i) position of the image formed and (ii) magnification of the image.
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Q20
short answer
2 marks
Consider a neutron (mass m) of kinetic energy E and a photon of the same energy. Let n and p be the de Broglie wavelength of neutron and the wavelength of photon respectively. Obtain an expression for pn.
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Q21
short answer
2 marks
Plot a graph showing the variation of current with voltage for the material GaAs. On the graph, mark the region where : (a) resistance is negative, and (b) Ohm's law is followed.
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Q23
short answer
3 marks
A cube of side 0·1 m is placed, as shown in the figure, in a region where electric field E = 500 x i exists. Here x is in meters and E in NC1. Calculate the flux passing through the cube.
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Q24
short answer
3 marks
Define current density. Is it a scalar or a vector? An electric field E is maintained in a metallic conductor. If n be the number of electrons (mass m, charge e) per unit volume in the conductor and its relaxation time, show that the current density j = E, where = m / ne2.
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Q25
short answer
3 marks
What is a Wheatstone bridge? Obtain the necessary conditions under which the Wheatstone bridge is balanced.
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Q25
long answer
3 marks
An inductor, a capacitor and a resistor are connected in series with an ac source v = vm sin wt. Derive an expression for the average power dissipated in the circuit. Also obtain the expression for the resonant frequency of the circuit.
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Q26
short answer
3 marks
A proton with kinetic energy 1·3384 10 14 J moving horizontally from north to south, enters a uniform magnetic field B of 2·0 mT directed eastward. Calculate the speed of the proton.
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Q26
long answer
3 marks
(a) Electromagnetic wave wavelength is often related to the characteristic size of the system producing the radiation. Give two examples to justify this statement. (b) (i) Long distance radio broadcasts use short-wave bands. Why? (ii) Optical and radio telescopes are built on the ground, but X-ray astronomy is possible only from satellites orbiting the Earth. Why?
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Q27
short answer
3 marks
A proton with kinetic energy 1·3384 10 14 J moving horizontally from north to south, enters a uniform magnetic field B of 2·0 mT directed eastward. Calculate the radius of the path traced by the proton. [Take (q/m) for proton = 1·0 108 C/kg]
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Q27
long answer
3 marks
Write the drawbacks of Rutherford's atomic model. How did Bohr correct them? Show that the distances between different orbits of Bohr atom are not equal.
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Q28
long answer
3 marks
(a) State any two properties of a nucleus. (b) Why is the density of a nucleus much more than that of an atom? (c) Show that the density of the nuclear matter is the same for all nuclei.
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A lens is a transparent medium bounded by two surfaces, with one or both surfaces being spherical. The focal length of a lens is determined by the radii of curvature of its two surfaces and the refractive index of its medium with respect to that of the surrounding medium. The power of a lens is reciprocal of its focal length. If a number of lenses are kept in contact, the power of the combination is the algebraic sum of the powers of the individual lenses.
Q32
mcq
1 mark
A double-convex lens, with each face having same radius of curvature R, is made of glass of refractive index n. Its power is :
- A. (n-1)/R
- B. 2(n-1)/R
- C. (n-1)/2R
- D. 2(2n-1)/R
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Q33
mcq
1 mark
A double-convex lens of power P, with each face having same radius of curvature, is cut into two equal parts perpendicular to its principal axis. The power of one part of the lens will be :
- A. 2P
- B. P
- C. 4P
- D. P/2
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Q34
mcq
1 mark
The above two parts are kept in contact with each other as shown in the figure. The power of the combination will be :
- A. P/2
- B. P
- C. 2P
- D. 4P
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Q35
mcq
1 mark
A double-convex lens of power P, with each face having same radius of curvature, is cut along its principal axis. The two parts are arranged as shown in the figure. The power of the combination will be :
- A. Zero
- B. P
- C. 2P
- D. P/2
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Q36
mcq
1 mark
Two convex lenses of focal lengths 60 cm and 20 cm are held coaxially in contact with each other. The power of the combination is :
- A. 6.6 D
- B. 15 D
- C. 1/15 D
- D. 1/80 D
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Junction Diode as a Rectifier : The process of conversion of an ac voltage into a dc voltage is called rectification and the device which performs this conversion is called a rectifier. The characteristics of a p-n junction diode reveal that when a p-n junction diode is forward biased, it offers a low resistance and when it is reverse biased, it offers a high resistance. Hence, a p-n junction diode conducts only when it is forward biased. This property of a p-n junction diode makes it suitable for its use as a rectifier. Thus, when an ac voltage is applied across a p-n junction, it conducts only during those alternate half cycles for which it is forward biased. A rectifier which rectifies only half cycle of an ac voltage is called a half-wave rectifier and one that rectifies both the half cycles is known as a full-wave rectifier.
Q37
mcq
1 mark
The root mean square value of an alternating voltage applied to a full-wave rectifier is V0/√2. Then the root mean square value of the rectified output voltage is :
- A. V0/√2
- B. V0^2/2
- C. 2√2V0
- D. V0/2√2
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Q38
mcq
1 mark
In a full-wave rectifier, the current in each of the diodes flows for :
- A. Complete cycle of the input signal
- B. Half cycle of the input signal
- C. Less than half cycle of the input signal
- D. Only for the positive half cycle of the input signal
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Q39
mcq
1 mark
In a full-wave rectifier :
- A. Both diodes are forward biased at the same time.
- B. Both diodes are reverse biased at the same time.
- C. One is forward biased and the other is reverse biased at the same time.
- D. Both are forward biased in the first half of the cycle and reverse biased in the second half of the cycle.
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Q40
mcq
1 mark
An alternating voltage of frequency of 50 Hz is applied to a half-wave rectifier. Then the ripple frequency of the output will be :
- A. 100 Hz
- B. 50 Hz
- C. 25 Hz
- D. 150 Hz
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Q41
mcq
1 mark
A signal, as shown in the figure, is applied to a p-n junction diode. Identify the output across resistance RL :
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Q42
long answer
5 marks
Derive an expression for potential energy of an electric dipole p in an external uniform electric field E. When is the potential energy of the dipole (1) maximum, and (2) minimum ?
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Q43
long answer
5 marks
An electric dipole consists of point charges 1·0 pC and + 1·0 pC located at (0, 0) and (3 mm, 4 mm) respectively in x y plane. An electric field E = 1000 V i is switched on in the region. Find the torque acting on the dipole.
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Q44
long answer
5 marks
An electric dipole (dipole moment p = p i ), consisting of charges q and q, separated by distance 2a, is placed along the x-axis, with its centre at the origin. Show that the potential V, due to this dipole, at a point x, (x >> a) is equal to p/4pi epsilon_0 x^2.
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Q45
long answer
5 marks
Two isolated metallic spheres S1 and S2 of radii 1 cm and 3 cm respectively are charged such that both have the same charge density. They are placed far away from each other and connected by a thin wire. Calculate the new charge on sphere S1.
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Q46
long answer
4 marks
A resistor and a capacitor are connected in series to an ac source v = vm sin wt. Derive an expression for the impedance of the circuit.
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Q47
short answer
4 marks
When does an inductor act as a conductor in a circuit ? Give reason for it.
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Q48
long answer
5 marks
An electric lamp is designed to operate at 110 V dc and 11 A current. If the lamp is operated on 220 V, 50 Hz ac source with a coil in series, then find the inductance of the coil.
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Q49
long answer
5 marks
Draw a labelled diagram of a step-up transformer and describe its working principle. Explain any three causes for energy losses in a real transformer.
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Q50
short answer
A step-up transformer converts a low voltage into high voltage. Does it violate the principle of conservation of energy ? Explain.
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Q51
short answer
5 marks
A step-up transformer has 200 and 3000 turns in its primary and secondary coils respectively. The input voltage given to the primary coil is 90 V. Calculate : (1) The output voltage across the secondary coil (2) The current in the primary coil if the current in the secondary coil is 2·0 A.
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Q52
long answer
5 marks
A ray of light passes through a triangular prism. Show graphically, how the angle of deviation varies with the angle of incidence ? Hence define the angle of minimum deviation.
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Q53
long answer
A ray of light is incident normally on a refracting face of a prism of prism angle A and suffers a deviation of angle δ. Prove that the refractive index n of the material of the prism is given by n = sin A / sin(A - δ).
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Q54
short answer
5 marks
The refractive index of the material of a prism is √2. If the refracting angle of the prism is 60°, find the (1) Angle of minimum deviation, and (2) Angle of incidence.
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Q55
long answer
5 marks
State Huygens principle. A plane wave is incident at an angle i on a reflecting surface. Construct the corresponding reflected wavefront. Using this diagram, prove that the angle of reflection is equal to the angle of incidence.
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Q56
short answer
What are the coherent sources of light ? Can two independent sodium lamps act like coherent sources ? Explain.
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Q57
short answer
5 marks
A beam of light consisting of a known wavelength 520 nm and an unknown wavelength λ experiment produces two interference patterns such that the fourth bright fringe of unknown wavelength coincides with the fifth bright fringe of known wavelength. Find the value of λ.
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