Q1
mcq
1 mark
An electron experiences a force (1·6 × 10^-16 N) i^ in an electric field E. The electric field E is :
- A. (1·0 × 10^3 N/C) i^
- B. (1·0 × 10^3 C/N) i^
- C. (1·0 × 10^-3 N/C) i^
- D. (1·0 × 10^-3 C/N) i^
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Q2
mcq
1 mark
Which one of the following is not a scalar quantity ?
- A. Electric field
- B. Voltage
- C. Resistivity
- D. Power
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Q3
mcq
1 mark
The current density due to drift of electrons in a conductor is given by : (symbols have their usual meanings)
- A. n e A vd
- B. e / n A vd
- C. e A / n vd
- D. n e vd
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Q4
mcq
1 mark
Which of the following graphs correctly represents the variation of the magnitude of the magnetic field outside a straight infinite current carrying wire?
- A. (graph)
- B. (graph)
- C. (graph)
- D. (graph)
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Q5
mcq
A particle of mass m and charge q moving with a uniform velocity v = v0x i + v0y j enters a region with a magnetic field B= B0 j . After some time, an electric field E = E0 j is also switched on in the region. The resulting path described by the particle will be :
- A. a circle in x-z plane
- B. a parabola in x-y plane
- C. a helix with constant pitch
- D. a helix with increasing pitch
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Q6
mcq
An inductor, a capacitor and a resistor are connected in series across an ac source of voltage. If the frequency of the source is decreased gradually, the reactance of :
- A. both the inductor and the capacitor decreases.
- B. inductor decreases and the capacitor increases.
- C. both the inductor and the capacitor increases.
- D. inductor increases and the capacitor decreases.
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Q7
mcq
The electromagnetic radiations used to kill germs in water purifiers are called :
- A. Infrared waves
- B. X-rays
- C. Gamma rays
- D. Ultraviolet rays
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Q8
mcq
In the wave picture of light, the intensity I of light is related to the amplitude A of the wave as :
- A. I A
- B. I A1/2
- C. I A^2
- D. I 2 A
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Q9
mcq
In a single-slit diffraction experiment, the width of the slit is halved. The width of the central maximum, in the diffraction pattern, will become :
- A. half
- B. twice
- C. four times
- D. one-fourth
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Q10
mcq
A graph is plotted between the stopping potential (on y-axis) and the frequency of incident radiation (on x-axis) for a metal. The product of the slope of the straight line obtained and the magnitude of charge on an electron is equal to :
- A. h
- B. c/h
- C. c/2h
- D. 2c/h
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Q10
mcq
For a metal. The product of the slope of the straight line obtained and the magnitude of charge on an electron is equal to :
- A. h
- B. c/h
- C. c/2h
- D. 2c/h
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Q11
mcq
Light of frequency 6·4 10^14 Hz is incident on a metal of work function 2·14 eV. The maximum kinetic energy of the emitted electrons is about :
- A. 0·25 eV
- B. 0·51 eV
- C. 1·02 eV
- D. 0·10 eV
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Q12
mcq
The ratio of maximum frequency and minimum frequency of light
- A. 9/11
- B. 5/9
- C. 7/11
- D. 7/16
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Q13
mcq
At a certain temperature in an intrinsic semiconductor, the electrons and holes concentration is 1·5 10^16 m^3...
- A. 3 10^6 m^3
- B. 5 10^7 m^3
- C. 5 10^9 m^3
- D. 6·75 10^38 m^3
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Q13
mcq
At a certain temperature in an intrinsic semiconductor, the electrons and holes concentration is 1.5 x 10^16 m^-3. When it is doped with a trivalent dopant, hole concentration increases to 4.5 x 10^22 m^-3. In the doped semiconductor, the concentration of electrons (ne) will be :
- A. 3 x 10^6 m^-3
- B. 5 x 10^7 m^-3
- C. 5 x 10^9 m^-3
- D. 6.75 x 10^38 m^-3
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Q14
mcq
If a p-n junction diode is reverse biased,
- A. the potential barrier is lowered.
- B. the potential barrier remains unaffected.
- C. the potential barrier is raised.
- D. the current is mainly due to majority carriers.
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Q15
mcq
A voltage signal is described by : v = V0 for 0 < t < T/2, v = 0 for T/2 < t < T for a cycle. Its rms value is :
- A. V0/2
- B. V0
- C. V0/sqrt(2)
- D. 2 V0
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Q16
short answer
Assertion (A) : The internal resistance of a cell is constant. Reason (R) : Ionic concentration of the electrolyte remains same during use of a cell.
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Q17
short answer
Assertion (A) : When radius of a circular loop carrying a steady current is doubled, its magnetic moment becomes four times. Reason (R): The magnetic moment of a circular loop carrying a steady current is proportional to the area of the loop.
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Q18
short answer
Assertion (A): The nucleus X(7,3) is more stable than the nucleus Y(4,3). Reason (R): X(7,3) contains more number of protons.
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Q19
short answer
2 marks
A wire of length l is in the form of a circular loop A of one turn. This loop is reshaped into loop B of three turns. Find the ratio of the magnetic fields at the centres of loop A and loop B for the same current through them.
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Q20
short answer
2 marks
Define displacement current. Briefly explain how this current is different from a conduction current.
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Q21
short answer
2 marks
(a) S le. How did Huygens explain the absence of the backwave?
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Q22
short answer
2 marks
The refractive indices of two media A and B are 2 and 2 respectively. What is the critical angle for their interface?
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Q23
short answer
2 marks
(a) Draw a graph showing the variation of binding energy per nucleon as a function of mass number A. The binding energy per nucleon for heavy nuclei (A 170) decreases with the increase in mass number. Explain.
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Q24
short answer
2 marks
Explain the roles of diffusion current and drift current in the formation of the depletion layer in a p-n junction diode.
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Q25
short answer
2 marks
Explain the property of a p-n junction which makes it suitable for rectifying alternating voltages. Differentiate between a half-wave and a full-wave rectifier.
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Q26
short answer
3 marks
A potential difference V is applied across a conductor of length l and uniform cross-section area A. How will the (i) electric field E, (ii) drift velocity vd, and (iii) current density j be affected when (a) V is doubled and (b) l is halved (keeping other factors constant)?
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Q27
short answer
3 marks
What is an expression for the mutual inductance of two long coaxial solenoids, each of length l but having different number of turns N1 and N2 and radii r1 and r2 (r2 > r1).
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Q28
short answer
3 marks
(a) An ac source v = vm sin t is connected across an ideal capacitor. Derive the expression for the (i) current flowing in the circuit, and (ii) reactance of the capacitor. Plot a graph of current i versus t.
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Q28
long answer
3 marks
(b) A series combination of an inductor L, a capacitor C and a resistor R is connected across an ac source of voltage in a circuit. Obtain an expression for the average power consumed by the circuit. Find power factor for (i) purely inductive circuit, and (ii) purely resistive circuit.
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Q29
long answer
3 marks
Calculate the wavelength of de Broglie waves associated with a proton having 500 eV energy. How will the wavelength be affected for an alpha particle having the same energy?
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Q30
long answer
3 marks
(a) (i) Prove that the nuclear density is same for all nuclei. (ii) Draw a plot of potential energy of a pair of nucleons as a function of their separation. Draw two inferences from this plot.
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Q30
long answer
3 marks
(b) (i) Draw a graph to show the variation of the number of scattered particles detected (N) in Geiger-Marsden experiment as a function of scattering angle ( ). (ii) Discuss briefly two conclusions that can be drawn from this graph and how they lead to the discovery of nucleus in an atom.
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Q31
long answer
5 marks
(a) (i) Define electric flux and write its SI unit. (ii) Use Gauss's law to derive the expression for the electric field due to a uniformly charged infinite plane sheet. (iii) A cube of side L is kept in space, as shown in the figure. An electric field E = (Ax + B) i^ exists in the region. Find the net charge enclosed by the cube.
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Q31
long answer
5 marks
(b) (i) Define electric potential at a point and write its SI unit. (ii) Two capacitors are connected in series. Derive an expression of the equivalent capacitance of the combination. (iii) Two point charges + q and q are located at points (3a, 0) and (0, 4a) respectively in x-y plane. A third charge Q is kept at the origin. Find the value of Q, in terms of q and a, so that the electrostatic potential energy of the system is zero.
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Q32
long answer
5 marks
(a) (i) Write the principle and explain the working of a moving coil galvanometer. A galvanometer as such cannot be used to measure the current in a circuit. Why ? (ii) Why is the magnetic field made radial ?
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Q38
long answer
5 marks
Why is the magnetic field made radial in a moving coil galvanometer ? How is it achieved ?
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Q39
long answer
5 marks
Derive an expression for magnetic field on the axis of a current carrying circular loop.
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Q40
long answer
5 marks
Write any two points of difference between a diamagnetic and a paramagnetic substance.
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Q41
long answer
5 marks
Draw a ray diagram showing the formation of a real image of (ii) A 1·8 m tall person stands in front of a convex lens of focal length 1 m, at a distance of 5 m. Find the position and height of the image formed.
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Q42
long answer
5 marks
Draw a ray diagram showing refraction of a ray of light through a triangular glass prism. Hence, obtain the relation for the refractive index ( ) in terms of angle of prism (A) and angle of minimum deviation ( m).
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Q43
long answer
5 marks
The radii of curvature of the two surfaces of a concave lens are 20 cm each. Find the refractive index of the material of the lens if its power is 5·0 D.
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A beam of electrons moving horizontally with a velocity of 3 107 m/s enters a region between two plates as shown in the figure. A suitable potential difference is applied across the plates such that the electron beam just strikes the edge of the lower plate.
Q44
short answer
1 mark
How long does an electron take to strike the edge ?
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Q45
short answer
1 mark
What is the shape of the path followed by the electron and why ?
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Q46
short answer
2 marks
Find the potential difference applied.
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Q47
short answer
2 marks
Find the magnitude and direction of the magnetic field which should be created in the space between the plates so that the electron beam goes straight undeviated.
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Diffraction of light is bending of light around the corners of an object whose size is comparable with the wavelength of light. Diffraction actually defines the limits of ray optics. This limit for optical instruments is set by the wavelength of light. An experimental arrangement is set up to observe the diffraction pattern due to a single slit.
Q48
short answer
1 mark
How will the width of central maximum be affected if the wavelength of light is increased ?
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Q49
short answer
1 mark
Under what condition is the first minimum obtained ?
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Q50
short answer
2 marks
Write two points of difference between interference and diffraction patterns.
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Q51
short answer
2 marks
Two students are separated by a 7 m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see each other even though they can converse easily ?
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