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GULF PHYSICS OLYMPIAD 2015 Class : 12 Total Marks : 90
Time Allotted: 90 mts
SET-1
1. Use ball point pen . 2. Answer by SHADING IN OMR SHEET 3. White ink and Ink killer is not Allowed.
1 An electron traveling horizontally enters a region where a uniform electric field is
directed upward. What is the direction of the force exerted on the electron once it has
entered the field?
(A) to the left
(B) out of the page, toward the reader
(C) upward
(D) downward
2 A conducting sphere has a net charge of -4.8 x 10-17C. What is the approximate
number of excess electrons on the sphere?
(A) 100
(B) 200
(C) 300
(D) 400
3 At which point (or points) is the electric field zero N/C for the two point charges shown
on the x axis?
(A) The electric field is never zero in the vicinity of these charges.
(B) The electric field is zero somewhere on the x axis to the left of the +4q charge.
(C) The electric field is zero somewhere on the x axis to the right of the - 2q charge.
(D) The electric field is zero somewhere on the x axis between the two charges, but this
point is nearer to the -2q charge.
4 A metallic shell has a point charge 'q' kept inside its cavity. Which one of the following
diagrams correctly represents the electric lines of forces
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(A)
(B)
(C)
(D)
5 The charge on an electron is known to be 1.6 x 10 -19coulomb. In a circuit the current
flowing is 1 A. How many electrons will be flowing through the circuit in a second?
(A) 1.6 x 1019
(B) 1.6 x 10-19
(C) 0.625 x 1019
(D) 0.625 x 10-12
6 Two bulbs marked 200 watt-250 volts and 100 watt-250 volts are joined in series to 250
volts supply. Power consumed in circuit is
(A) 33 watt
(B) 67 watt
(C) 100 watt
(D) 300 watt
7 A copper wire of length l and diameter d has potential difference V applied at its two
ends. The drift velocity is dV . If the diameter of wire is made d/3, then drift velocity
becomes
(A) 9 dV
(B) dV / 9
(C) dV /3
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(D) dV
8 In the given circuit diagram, what is the dc source voltage?
(A)
78 V
(B) 39 V
(C) 13 V
(D) 0 V
9 Resistances R1 and R2 are connected respectively in the left gap and right gap of a metre
bridge. If the balance point is located at 55 cm, the ratio R2/R1 is
(A) 4/5
(B) 5/4
(C) 9/11
(D) 11/9
10 A battery of emf V volt is connected to a combination of four identical capacitors (each
of capacitance C farad) arranged as shown in the adjoining figure. What is the amount of
energy supplied by the battery to the capacitor combination?
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(A) CV2/4
(B) CV2/2
(C) CV2/3
(D) 2CV2/3
11 A parallel plate capacitor with air as dielectric has capacitance C. It is charged fully
using a battery of emf V. The battery is then disconnected and the separation between
the plates of the capacitor is doubled. What is the final energy stored in the capacitor?
(A) ½ CV2
(B) CV2
(C) 3CV2/2
(D) 2 CV2
12 If the rms voltage drop across a 15 k resistor is 16 V, the peak current through the
resistor is
(A) 15 mA
(B) 1.5 mA
(C) 10 mA
(D) 1 mA
13 A coil consisting of 50 turns of copper wire has an area of 30 cm2. Determine the peak
magnitude of the sinusoidal voltage produced across the terminals of the coil if it rotates
within a magnetic field of 700 mT at a rate of 3000 rpm?
(A) 5.25 V
(B) 13 V
(C) 25 V
(D) 33 V
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14
Which of the following correctly lists electromagnetic waves in order from longest to
shortest wavelength?
(A) gamma rays, ultraviolet, infrared, microwaves
(B) microwaves, ultraviolet, visible light, gamma rays
(C) radio waves, infrared, gamma rays, ultraviolet
(D) television, infrared, visible light, X-rays
15 An electromagnetic wave is traveling to the east. At one instant at a given point
its E vector points straight up. What is the direction of its B vector?
(A) north
(B)down
(C) east
(D)south
16 The length of a microscope is 12 cm and its magnifying power is 25 for relaxed eye. The
focal length of the eye piece is 4 cm. The distance of the object from the objective is
(A) 2 cm
(B) 2.5 cm
(C) 3 cm
(D) 3.5 cm
17 What wavelength from the electromagnetic spectrum has the longest wavelength?
(A) Visible light
(B) X-rays
(C) Radio waves
(D) Gamma rays
18 The magnifying power of a small telescope is 25 and the separation between its
objective and eye piece is 52 cm in normal setting. The focal lengths of its objective and
eye piece are respectively
(A) 50 cm and 2 cm
(B) 27 cm and 25 cm
(C) 45 cm and 7 cm
(D) 50.5 cm and 1.5 cm
19 What is the emf induced when a 18cm
conducting rod attached to a U-shaped
conductor moves at a speed of 1cm/s
perpendicular to a magnetic field of
strength 37.5 T?
(A) 3.0V
(B) 2.1V
(C) 0.07V
(D) 0.03V
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20 What are the possible dimensions for a rectangular coil that has a magnetic flux of 9.5
Weber when in a magnetic field of strength 19T at an angle of 600 from the
perpendicular to the plane of the coil?
(A) 80cm 70cm
(B) 360cm30cm
(C) 120cm80cm
(D) 1000cm 100cm
21 When the frequency of the source voltage decreases, the impedance of a parallel RC
circuit
(A) increases
(B) does not change
(C) decreases to zero
(D)decreases
22 In a Young's double-slit experiment, the slit separation is doubled. To maintain the same
fringe spacing on the screen, the screen-to-slit distance D must be changed to
(A) D/2
( B) D/ 2
(C) 2 D
(D) 2D
23 A moving coil galvanometer of resistance 100 Ω is used as an ammeter using a
resistance 0.1Ω. The maximum deflection current in the galvanometer is 100 μA. Find
the current in the circuit, so that the ammeter shows maximum deflection.
(A) 10.01A
(B) 100.1A
(C) 1.01A
(D) 1000.1A
24 An electric field due to a positive charge is
represented by the diagram. Which of the
following points has higher potential?
(A) A
(B)B
(C) C
(D)D
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25 A non-uniform electric field is represented
by equipotential lines. How much work is
done by the electric field when a positive
charge of magnitude 1 µC moves from point
A to point E?
(A) 0 µJ
(B) 20 µJ
(C) 40 µJ
(D) 60 µJ
26 In Young’s experiment , the distance between two slits is d/3 and the
distance between the screen and the slit is 3D . The number of fringes in 1/3 m
on the screen , formed by monochromatic light of wavelength 3 λ , will be
A) D / 9Dλ
B) d / 27 D λ
C) d / 81 D λ
D) d/ D λ
27 The path difference between two interfering waves at a point on the screen is
λ / 8 . The ratio of intensity at this point and that at the central fringe will be
A) 0.853
B) 8.53
C) 85.3
D) 853
28 Focal length of a convex lens of refractive index 1.5 is 2 cm. Focal length of
this lens when immersed in a liquid of refractive index of 1.25 will be
A) 10 cm
B) 2.5 cm
C) 5 cm
D) 7.5 cm
29 Angle of minimum deviation for a prism of refractive index 1.5 , is equal to
the angle of the prism .Then the angle of the prism is (Given cos 41 o = 0.75)
A) 62 o
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B) 41o
C) 82 0
D) 31 o
30 The magnification produced by an astronomical telescope for normal
adjustment is 10 and the length of the telescope is 1.1 m. The magnification
when the image is formed at least distance of distinct vision (D = 25 cm ) is
A) 6
B) 14
C) 18
D) 16
31 X-rays are used to irradiate sodium and copper surfaces in two separate
experiments and stopping potential determined . This stopping potential is
A) Equal in both cases
B) greater for sodium
C) greater for copper
D) infinite in both cases
32 If α – particle and proton are accelerated through the same potential difference
, then the ratio of de – Broglie wavelength of α –particle and proton is
A) 2
B)
C)
D)
33 The correct curve between the stopping potential Vs and intensity of incident
light I is
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34 The threshold wavelength for photoelectric emission from a material is 4800
Ao . Photoelectrons will be emitted from the material , when it is illuminated
with light from a
(A) 40 W blue lamp
(B) 40 W green lamp
(C)100 W yellow lamp
(D ) 100 W red lamp
35 In an atom , the two electrons move round the nucleus in circular orbits of
radii R and 4 R . The ratio of the time taken by them to complete one
revolution is
(A) 1/4
(B ) 4/1
(C ) 8/1
( D) 1/8
36
37
The ratio of minimum to maximum wavelength in Balmer series is
(A) 5 : 9
(B) 5 : 36
(C) 1 : 4
(D) 3: 4
The graph is a plot of binding energy per nucleon Eb against the nuclear mass
M. A, B, C , D , E , F correspond to different nuclei. Consider four reactions
( i )A+B C + ε (ii ) C A + B + ε
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(iii )D + E F + ε ( iv )F D + E + ε
Where ε is the energy released.
In which reaction is ε positive ?
(A) (i) and (iii)
(B) (ii) and (iv)
(C ) (ii) and (iii)
(D) (i) and (iv)
38 The ground state energy of hydrogen atom is – 13.6 e V . What is the potential
energy of the electron in this state ?
(A) 0 eV
(B) – 27.2 eV
(C) 1 eV
( D) 2 eV
39 A radioactive element X with half life 2 hours decays giving a stable element
Y . After a time t , ratio of X and Y atoms is 1 : 16 . Time t is
(A) 6 hrs
(B) 4 hrs
(C ) 8 hrs
( D ) 16 hrs
40
The wavelength of matter wave is independent of
(A) Mass
(B) velocity
( C) momentum
(D) charge
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41 If a semiconductor has an intrinsic carrier concentration of
1.41 x 1016 / m3 when doped with 1021 / m3 phosphorus atoms , then the
concentration of holes / m3 at room temperature will be
(A) 2x 1021
(B) 2x 1011
(C) 1.41 x 1010
(D) 1.41x 10 16
42 In a common emitter amplifier , using output resistance of 5000 Ω and input
resistance of 2000 Ω , if the peak value of input signal voltage is 10 mV and β
= 50 , then peak value of output voltage is
(A) 5 x 10 -6 V
(B) 12.5 x 10 -4 V
(C) 1.25 V
(D) 125 V
43 In a npn transistor , the collector current is 10 mA. If 90 % of the electrons
emitted reach the collector , then the emitter current will be
(A) 9mA
(B)11mA
(C)1mA
(D)0.1mA
44 In the following circuit the output Y becomes zero for the input
A A
B
Y
C
(A) A= 1 , B = 0 , C = 0
(B) A=0 ,B=1 , C=1
(C)A = 1 , B = 1 , C = 0
(D) A =0 ,B=1 ,C=0
45 A photodetector used to detect the wavelength of 1700 nm , has energy gap of
about
(A) 0.73 eV
(B) 0.073 eV
(C) 7.3 eV
(D) 1.16eV
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46
Intelsat satellite works as a
(A)Transmitter
(B) Repeater
(C)Absorber
(D) None of the above
47 Which one of the following is correct ?
(A) A single geostationary satellite can cover the whole part of the earth for
microwave communication
(B) Atleast three geostationary satellites in the same orbit around earth can
cover the whole part of the earth for microwave communication
(C) The first Indian communication satellite is Apple
(D) The satellite communication is not like the line of sight microwave
communication.
48 A TV tower has a height of 75 m . What is the maximum area upto which this
TV communication can be possible ?
(A) 1509 km2
(B)3018 km2
(C)2254 km2
D)6036km2
49 The length of a half wave dipole at 30 megahertz is
(A) 10 m
(B)50 m
(C) 5 m
(D) 100 m
50 In amplitude modulation , if modulation index is more than 100 % , then
(A) Efficiency increases
(B) power increases
(C) the wave gets distorted
(D) none of the above
51.The energy of infra red rays is greater than that of
(A) X –rays.
(B) visible light
(C) Microwaves
(D) gamma rays
52. A concave lens and a convex lens separated by a distance d are then put into contact .The
focal length of the combination.
(A) decreases
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(B) increases
(C) becomes zero
(D)remains the same.
53.In a LCR circuit, the capacitance is changed from C to 2C.For the resonant frequency to
remain unchanged ,the inductance should be changed from L to
(A) 4L
(B) 2L
(C) L/2
(D) L/4
54. In a LCR circuit, the voltage across each of the components L,C, and R is 50V.The voltage
across the LC combination will be
(A)50V
(B)zero
(C)50√2 V
(D) 100V
55. Which among the following cannot be polarized?
(A) Infra red rays.
(B) ultrasonic waves
(C) visible light
(D) micro waves
56. Which among the following works under forward bias?
(A) Photodiode
(B) Zener diode
(C) Solar cell
(D) PN junction diode
57. The following statements describes the size and level of doping in the three components
of a transistor which of them is not true.
(A) emitter is heavily doped and moderate in size.
(B) collector is moderately doped and larger in size
(C) emitter is moderately doped and moderate in size.
(D) base is thin and lightly doped.
58. Two nuclei have their mass numbers in the ratio 8: 1. The ratio of their nuclear densities is
(A) 8:1
(B) 64:1
(C) 2:1
(D) 1:1
59.What is the deBroglie wavelength of an electron accelerated by 100V is
(A) 1.227A
(B) 122.7 A