Q1
mcq
1 mark
1. In a region, the electric potential varies as V = 10 – 50x, where V is in volts and x in meters. The electric field in the region is
- A. 10 N/C along +x
- B. 10 N/C along –x
- C. 50 N/C along +x
- D. 50 N/C along –x
Solution hidden
Log in to view solution →
Q2
mcq
1 mark
2. A conducting wire connects two charged metallic spheres A and B of radii r1 and r2 respectively. The distance between the spheres is very large compared to their radii. The ratio of electric fields, (EA /EB ) at the surfaces of spheres A and B will be
- A. r1/r2
- B. r2/r1
- C. r1^2/r2^2
- D. r2^2/r1^2
Solution hidden
Log in to view solution →
Q3
mcq
1 mark
3. A long straight wire of circular cross-section (radius a) carries a steady current I. The current is uniformly distributed across this cross-section. The magnitude of the magnetic field produced at a point at a distance (a/2) from the axis of the wire will be
- A. Zero
- B. μ0I / 2πa
- C. μ0I / 4πa
- D. μ0I / 6πa
Solution hidden
Log in to view solution →
Q4
mcq
1 mark
4. The shape of the interference fringes in Young’s double-slit experiment, when the distance between the slit and the screen is very large as compared to the slit-separation, is nearly
- A. straight
- B. parabolic
- C. circular
- D. hyperbolic
Solution hidden
Log in to view solution →
Q5
mcq
1 mark
5. An electromagnetic wave passes from vacuum into a dielectric medium with relative electrical permittivity (3/2) and relative magnetic permeability (8/3). Then, its
- A. wavelength is doubled and frequency remains unchanged.
- B. wavelength is doubled and frequency is halved.
- C. wavelength is halved and frequency remains unchanged.
- D. wavelength and frequency both will remain unchanged.
Solution hidden
Log in to view solution →
Q6
mcq
1 mark
6. In a series LCR circuit, the voltage across the resistor, capacitor and inductor is 10 V each. If the capacitor is short circuited, the voltage across the inductor will be
- A. 10 V
- B. 5√2 V
- C. 5/√2 V
- D. 10√2 V
Solution hidden
Log in to view solution →
Q7
mcq
1 mark
7. Electromagnetic waves used in a diagnostic tool in medicine have a wavelength range
- A. 1 nm to 10–3 nm
- B. 400 nm to 1 nm
- C. 1 mm to 700 nm
- D. 0.1 m to 1 mm
Solution hidden
Log in to view solution →
Q8
mcq
1 mark
The ‘distance of closest approach’ of an alpha-particle is ‘d’ when it moves with a velocity head-on towards the target nucleus. If the velocity of alpha particle is halved, the new ‘distance of closest approach’ will be
- A. d/2
- B. 2d
- C. d/4
- D. 4d
Solution hidden
Log in to view solution →
Q9
mcq
1 mark
A concave lens of focal length 10 cm is cut into two identical plano-concave lenses. The focal length of each lens will be
- A. 20 cm
- B. 30 cm
- C. 40 cm
- D. 5 cm
Solution hidden
Log in to view solution →
Q10
mcq
1 mark
Four independent waves are expressed as (i) y1 = A1 sin t (ii) y2 = A2 sin 2 t (iii) y3 = A3 cos t (iv) y4 = A4 sin (t + /3). The interference between two of these waves is possible in
- A. (i) and (iii) only
- B. (iii) and (iv) only
- C. (i), (iii) and (iv) only
- D. All of them
Solution hidden
Log in to view solution →
Q11
mcq
1 mark
Two heaters rated as (P1, V) and (P2, V) are connected in series across a dc source of V2 volt. The power consumed by the combination will be
- A. (P1 + P2)
- B. (P1 + P2)/2
- C. P1 P2 / 2(P1 + P2)
- D. P1 P2 / 4(P1 + P2)
Solution hidden
Log in to view solution →
Q12
mcq
1 mark
In an unbiased p-n junction, at equilibrium, which of the following statements is true ?
- A. Diffusion current is zero but drift current exists.
- B. Diffusion current exists but drift current is zero.
- C. Diffusion and drift currents are equal and opposite.
- D. Both the diffusion and drift currents exist but are unequal.
Solution hidden
Log in to view solution →
Q13
short answer
1 mark
Assertion (A) : All atoms have a net magnetic moment. Reason (R) : A current loop does not always behave as a magnetic dipole.
Solution hidden
Log in to view solution →
Q14
short answer
1 mark
Assertion (A) : If accelerated electrons are passed through a narrow slit, a diffraction pattern is observed. Reason (R) : Electrons behave as both particles and waves.
Solution hidden
Log in to view solution →
Q15
short answer
1 mark
Reason (A) : The mass of a nucleus is less than the sum of the masses of the constituent nucleons. Reason (R) : Energy is absorbed when the nucleons are bound together to form a nucleus.
Solution hidden
Log in to view solution →
Q16
short answer
1 mark
Reason (A) : In Bohr model of hydrogen atom, the energy levels are discrete and quantised. Reason (R) : In a hydrogen atom, the electrostatic force on the electron provides the necessary centripetal force to it to revolve around the nucleus.
Solution hidden
Log in to view solution →
Q17
short answer
2 marks
In a photoelectric experiment, the emitter plate is irradiated with radiation of 200 nm. The photocurrent becomes zero when the collector plate potential is – 0.80 V. Calculate the work function (in eV) of the emitter.
Solution hidden
Log in to view solution →
Q18
short answer
2 marks
A beam of light consisting of two wavelengths 400 nm and 600 nm is used to illuminate a single slit of width 1 mm. Find the least distance of the point from the central maximum where the dark fringes due to both wavelengths coincide on the screen placed 1.5 m from the slit.
Solution hidden
Log in to view solution →
Q19
short answer
2 marks
In a Young’s double-slit experimental set-up with slit separation 0.6 mm a beam of light consisting of two wavelengths 440 nm and 660 nm is used to obtain interference pattern on a screen kept 1.5 m in front of the slits. Find the least distance of the point from the central maximum where the bright fringes due to both the wavelengths coincide.
Solution hidden
Log in to view solution →
Q19
short answer
2 marks
A wire of length L is bent round into (i) a square coil having N turns and (ii) a circular coil having N turns. The coil in both cases is free to turn about a vertical axis coinciding with the plane of the coil, in a uniform, horizontal magnetic field and carry the same currents. Find the ratio of the maximum value of the torque acting on the square coil to that on the circular coil.
Solution hidden
Log in to view solution →
Q20
short answer
2 marks
What is the order of magnitude of drift velocity of electrons in a conductor ? Deduce the relation between the current flowing through a conductor and drift velocity of electrons in it.
Solution hidden
Log in to view solution →
Q21
short answer
2 marks
Draw the plot of potential energy of a pair of nucleons as a function of their separation. Write two important conclusions that can be drawn from this plot.
Solution hidden
Log in to view solution →
Q23
long answer
3 marks
Using Gauss’s law, deduce an expression for electric field at a point due to a uniformly charged infinite plane thin sheet.
Solution hidden
Log in to view solution →
Q23
long answer
3 marks
A parallel plate capacitor of capacitance C has a dielectric slab between its plates. It is charged to a potential difference V by connecting it across a battery. The battery is then disconnected. If the dielectric slab is now withdrawn from the capacitor, how will the following be affected? (a) Capacitance of the capacitor, (b) Energy stored in the capacitor, and (c) The potential difference between the plates of the capacitor. Justify your answer in each case.
Solution hidden
Log in to view solution →
Q24
long answer
Two large thin plane sheets, each having surface charge density are held close and parallel to each other in air. What is the net electric field at a point (i) inside and (ii) outside, the sheets ?
Solution hidden
Log in to view solution →
Q24
long answer
3 marks
Figure shows a narrow beam of electrons entering with a velocity of 3 x 10^7 m/s, symmetrically through the space between two parallel horizontal plates P1 P1' and P2 P2' kept 2 cm apart. If each plate is 3 cm long, calculate the potential difference V.
Solution hidden
Log in to view solution →
Q25
long answer
Obtain the condition of balance of a Wheatstone bridge.
Solution hidden
Log in to view solution →
Q25
short answer
3 marks
An ac voltage Vi = 12 sin (100 pi*t) V is applied between points A and B in a network of two ideal diodes and three resistors as shown in figure. During the positive half-cycle of the input voltage Vi supplied to the network. (a) Identify which of the two diodes will conduct and why? (b) Redraw an equivalent circuit diagram to show the flow of current. (c) Calculate the output voltage drops V0 across the three resistors when the input voltage attains its peak value.
Solution hidden
Log in to view solution →
Q26
long answer
Find net resistance of the network of resistors connected between A and B, as shown in figure.
Solution hidden
Log in to view solution →
Q26
short answer
3 marks
Briefly explain the two important processes that occur during the formation of a p-n junction.
Solution hidden
Log in to view solution →
Q27
short answer
3 marks
(a) Draw the ray diagram to show the image formation by a refracting telescope and write the expression for angular magnification for the telescope in normal adjustment. (b) Give two reasons to explain why a reflecting telescope is preferred over a refracting telescope.
Solution hidden
Log in to view solution →
Q28
short answer
3 marks
(a) State the two conditions under which total internal reflection occurs. (b) A transparent container contains layers of three immiscible transparent liquids A, B and C of refractive indices n, 3/4 n and 2/3 n, respectively. A laser beam is incident at the interface between A and B at an angle theta as shown in figure. Prove that the beam does not enter region C at all for sin theta > 2/3.
Solution hidden
Log in to view solution →Reading Passage
A galvanometer is used to detect or/and measure small currents in an electrical circuit. It essentially works on the fact that a current-carrying coil experiences a deflecting torque when placed in a magnetic field. This deflection in the coil can be measured and it is related to the current flowing in the coil, the number of turns in the coil, area of the coil and the magnetic field. A hair spring attached to the coil provides a counter torque and helps in measuring the deflection. A galvanometer can be converted to an ammeter or a voltmeter of desired range by using suitable resistances.
Q29
short answer
4 marks
A galvanometer is used to detect or/and measure small currents in an electrical circuit. It essentially works on the fact that a current-carrying coil experiences a deflecting torque when placed in a magnetic field. This deflection in the coil can be measured and it is related to the current flowing in the coil, the number of turns in the coil, area of the coil and the magnetic field. A hair spring attached to the coil provides a counter torque and helps in measuring the deflection. A galvanometer can be converted to an ammeter or a voltmeter of desired range by using suitable resistances.
Solution hidden
Log in to view solution →
Q31
long answer
5 marks
(a) An electric dipole consists of two point charges q and –q separated by a distance 2a. Derive an expression for the electric field E due to this dipole at a point distant r from the centre of the dipole on the equatorial plane. Write the expression for the electric field at a far off point, i.e. r >> a. (b) A dipole is placed in x-y plane such that charges q and –q are located at x = a and x = b respectively. There exists an electric field E = 2i N/C in the region. Calculate the force F and torque τ experienced by the dipole.
Solution hidden
Log in to view solution →
Q32
long answer
5 marks
(a) Using the relation for refraction at a curved spherical surface, derive the expression for lens maker’s formula. (b) Three lenses L1, L2 and L3, each of focal length 40 cm, are placed coaxially. The distance between L1 and L2 and between L2 and L3 are 120 cm and 20 cm respectively. An object is kept at a distance of 80 cm to the left of lens L1. Find the distance of the final image formed from the object.
Solution hidden
Log in to view solution →
Q33
long answer
5 marks
(a) State Faraday’s law of electromagnetic induction. (b) Derive an expression for the self-inductance of an air-filled long solenoid of length l and cross-sectional area A having N turns. (c) A conducting rod of length 50 cm, with one end pivoted, is rotated with angular speed of 60 rpm in a uniform magnetic field of 4.0 mT directed perpendicular to the plane of rotation of rod. Find the emf induced in the rod.
Solution hidden
Log in to view solution →
Q34
mcq
The torque on the coil remains constant irrespective of the coil’s orientation during rotation due to
- A. use of soft iron core which increases the magnetic field.
- B. radial magnetic field
- C. hair spring which provides the counter torque
- D. eddy current in the iron core which causes damping.
Solution hidden
Log in to view solution →
Q35
mcq
The best way to increase current sensitivity of a galvanometer is by
- A. increasing number of turns of the coil
- B. increasing area of coil and magnitic field strength
- C. decreasing area of coil and magnetic field strength
- D. increasing torsional constant of the hair spring
Solution hidden
Log in to view solution →
Q36
mcq
A moving coil galvanometer has a coil with area of cross-section 4.0 x 10–3 m2 and number of turns 50. The coil is rotating in a magnetic field of 0.25 T. The torque acting on the coil when a current of 5 A passes through it is
- A. 1.0 N m
- B. 2.0 N m
- C. 0.50 N m
- D. 0.25 N m
Solution hidden
Log in to view solution →
Q37
mcq
A galvanometer coil has a resistance of 15 Ω and the meter shows full scale deflection for a current of 3 mA. The value of resistance required to convert it into a voltmeter of range (0 – 12 V) is
- A. 4015 Ω
- B. 3985 Ω
- C. 415 Ω
- D. 385 Ω
Solution hidden
Log in to view solution →
Q38
mcq
A galvanometer with coil of resistance 20 Ω shows full scale deflection for a current of 5 mA. To convert it into an ammeter of range (0 – 10 A), a resistance of
- A. 0.05 Ω should be connected in series with it.
- B. 0.05 Ω should be connected in parallel with it.
- C. 0.01 Ω should be connected in parallel with it.
- D. 0.01 Ω should be connected in series with it.
Solution hidden
Log in to view solution →
Q39
mcq
From the graph, the work functions of A and B are (h is Planck’s constant and e value of charge on an electron)
- A. ν1 and ν2
- B. V1 and V2
- C. hν1 and hν2
- D. hν1/e and hν2/e
Solution hidden
Log in to view solution →
Q40
mcq
For radiation of frequency ν > ν2 incident on the surfaces of A and B, the maximum kinetic energy of ejected electron is
- A. greater for metal A because it has a smaller work function.
- B. greater for metal B because it has a larger work function.
- C. greater for metal B because it has higher threshold frequency.
- D. the same for both metal A and metal B because it is independent of work functions of metals.
Solution hidden
Log in to view solution →
Q41
mcq
If the intensity of the incident radiation for both metals A and B, is doubled keeping its frequency constant, then
- A. the slope of the parallel lines will increase.
- B. the slope of the parallel lines will decrease.
- C. the threshold frequencies for both A and B will decrease.
- D. the slope of the parallel lines will not change but more electrons will be emitted per second.
Solution hidden
Log in to view solution →
Q42
mcq
The threshold frequency for a metal surface is ν0. If the radiation of frequency 3ν0 illuminates the surface, the maximum kinetic energy (KE) of photoelectrons is E1. If the frequency were increased to 60, the maximum KE of the photoelectrons becomes E2. Then E1/E2 equals
- A. 1/3
- B. 1/2
- C. 2/5
- D. 3/4
Solution hidden
Log in to view solution →
Q43
mcq
Let m be the slope of the graph line for metal B. If e is the value of electron charge, then Planck’s constant ‘h’ is given by
- A. me
- B. 1/me
- C. m/e
- D. e/m
Solution hidden
Log in to view solution →
Q47
long answer
5 marks
(a) State Faraday’s law of electromagnetic induction. (b) Derive an expression for the self-inductance of an air-filled long solenoid of length l and cross-sectional area A having N turns.
Solution hidden
Log in to view solution →
Q48
long answer
A conducting rod of length 50 cm, with one end pivoted, is rotated with angular speed of 60 rpm in a uniform magnetic field of 4.0 mT directed perpendicular to the plane of rotation of rod. Find the emf induced in the rod.
Solution hidden
Log in to view solution →
Q49
long answer
OR (a) Draw a labelled diagram of a step-up transformer. State the principle on which it works and obtain the ratio of secondary voltage to primary voltage in terms of number of turns and currents in the two coils.
Solution hidden
Log in to view solution →
Q50
short answer
(b) The ratio of the number of turns in the primary to the secondary of an ideal transformer is 1 : 5. If 5 kW power at 200 V is supplied to the primary, find (i) current in the primary
Solution hidden
Log in to view solution →