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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

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(C) 12.27 A

(D) 0.1227 A

60. The refractive index and permeability of a medium are respectively 1.5 & 5x10-7 H/m. The

relative permittivity of the medium is nearly

(A)25

(B)15

(C)6

(D)81