Dpmt 2007 Physics

DPMT - 2007 PHYSICS 1.

In the potentiometer experiment the are 10 lines in the potentiometer. In first situation null point is at 7th line. If we want to obtain the null point in the 9th line then it can be done by (1) increasing resistance R in series with the battery whose e.m.f. is to be measured (2) decreasing resistance R in series with the battery whose e.m.f. is to be measured (3) increasing resistance R in main circuit (4) decreasing resistance R in main circuit

Sol: Ans [3] 2.

When in hydrogen like ion electron jumps from n = 3 to n = 1 emitted photon has frequency 2.7 × 1015 Hz. When electron jumps from n = 4 to n = 1, the frequency is (1) 1.6 × 1015

(2) 2.8 × 1015

(3) 6.4 × 1015

(4) 4.8 × 1015

Sol: Ans [2]

y A

3.

B

O

x

Standing wave shown in the figure, point A and B reach at y = 0 (1) in same time

(2) time difference is T/4 (B is lagging)

(3) time difference is T/2 (B is lagging)

(4) time difference is T/4 (A is lagging)

Sol: Ans [1] 4.

Reverberation time can’t be controlled by (1) temperature

(2) size of window

(3) volume of room

(4) changing carpet

Sol: Ans [1] 5.

Number of neutron emitted per fission is 1.6 when the energy released per fission is 200 MeV. The number of neutrons emitted per second when 20 MW power is generated (1) 3.9 × 1020

(2) 3.9 × 1019

(3) 1019

(4) 1018

Sol: Ans [4] 6.

Mass of proton is 1.6 × 10–27 kg. The proton enters in the magnetic field of 2 T at an angle 30° with direction of field. The velocity of proton is 2 × 107 m/s. The radius of path described by proton is (1) 3 cm

(2) 4 cm

(3) 5 cm

(4) 6 cm

Sol: Ans [3] Amity Institute for Competitive Examinations : Phones: 24336143/44, 25573111/2/3/4, 95120-2431839/42 -1-

Physics

7.

DPMT-2007

Electron is moving perpendicular to z-axis the magnetic field B0 is present along the z-axis the radius of circular path is a. Angular momentum is (1) eB0 a 2

(3) e2 B0 2 a 2

(2) 0

(4) eB0 a

Sol: Ans [1] 8.

In common base transistor, characteristic curve is Ie

Ie

10 V

10 V

Ie

20 V

20 V

(1)

(2)

(3)

Vbe

Vbe

Ie

10 V 20 V

10 V 20 V

(4)

Vbe

Vbe

Sol: Ans [2] 9.

A ball is dropped from height h on the ground where coefficient of restitution is e. After one bounce the maximum height is (1) e2 h

(2)

e h

(3) eh

(4)

eh

Sol: Ans [1] 10. An object of length 2.5 cm is placed at the principal axis is concave mirror at a distance 1.5 f. The image height is (1) + 5cm

(2) – 5 cm

(3) –1 cm

(4) + 1 cm

Sol: Ans [2] 11.

If µs is coefficient static friction and µk is coefficient of kinetic friction then (1) no relation between µs and µk

(2) generally µs > µk

(3) generally µs = µk

(4) generally µs < µk

Sol: Ans [2] 12. No force is required for (1) an object moving is straight line with constant velocity (2) an object moving in circular motion (3) an object moving with constant acceleration (4) an object moving in elliptical path Sol: Ans [1] 13. For four basic forces, maximum and minimum range is of (1) gravitational, nuclear

(2) weak, electromagnetic

(3) gravitational, electromagnetic

(4) electromagnetic, gravitational

Sol: Ans [1]

Amity Institute for Competitive Examinations : Phones: 24336143/44, 25573111/2/3/4, 95120-2431839/42 -2-

DPMT-2007

Physics

14. Kinetic energy of particles of mass 10 g and 40 gm is same, the ratio of their linear momentum (1) 1/4

(2) 1/2

(3) 1/ 2

(4)

2 /1

Sol: Ans [2] 15. Moment of inertia of a ring about is diameter is I the moment of inertia of the same ring about the axis perpendicular to its plane and passing through centre is (1) I/2

(2) 2I

(3) I/4

(4) 4I

Sol: Ans [2] 16. The acceleration due to gravity at a depth d is g d and at height h above the surface of earth is g h . If d = 2h, then the ratio g d /g h is equal to (1) 1

(2) 1/2

(3) 2/1

(4) 1/4

Sol: Ans [1] 17. A lift accelerates upward then deaccelerates and stops at higher floor. The apparent weight of the body in the later parts of its motion is (1) more than actual weight

(2) less than actual weight

(3) no change

(4) equal to actual weight

Sol: Ans [2] 18. Cu and Al wire each of length l = 20 cm and Area of cross section A = 50 mm2 . Their resistivity ρ Cu = 1.69 × 10–8 Ωm and ρ Al = 2.75 × 10–8 Ωm. If they are joined end to end then total resistance of combination is (1) 0.01 × 10–2

(2) 4.44

(3) 0.888

(4) 1 × 10–2

Sol: Ans [1] 19. According to uncertainty principle for an electron time measurement will become uncertain if following is measured with high certainty (1) energy

(2) momentum

(3) location

(4) velocity

Sol: Ans [1] 20. 12 V battery is applied in forward bias across a circuit having PN junction and resistance R in series. 0.6 V potential is drop across PN junction, and current is 2 × 10–3 amp. The resistance R is (1) 5.7 × 102

(2) 5.7 × 103

(3) 5.7 × 104

(4) 5.7 × 105

Sol: Ans [2] 21. When two springs of spring force constant K and 2K are connected in series then force constant becomes KS, if they are connected in parallel then force constant becomes Kp . Ratio Ks /Kp is (1) 2/9

(2) 1/2

(3) 2/1

(4) 1/3

Sol: Ans [1]

Amity Institute for Competitive Examinations : Phones: 24336143/44, 25573111/2/3/4, 95120-2431839/42 -3-

Physics

DPMT-2007

22. And inductor of inductance 10 H is connected in series with a resistance R = 6 ohm. A 12 volt battery is connected for a long time. When the circuit is switched off, the induced emf in inductor, if current reduces to zero in 10 ms, is (1) 1000 V

(2) 2000 V

(3) 3000 V

(4) 4000 V

Sol: Ans [2] 23. Series AC circuit has inductance L, resistance R and angular frequency ω, the quality factor Q is (1)

 ωL     R 

2

(2)

ωL R

(3)

R ωL

(4)

 R     ωL 

2

Sol: Ans [2] 24. At a certain place on earth BH = 1/ 3 BV dip angle is (1) 60°

(2) 30°

(3) 45°

(4) 90°

Sol: Ans [1] 25. For a wave to under go total internal reflection (iC is critical angle and i incidence angle) (1) light moves from rarer to denser medium and i > iC (2) light moves from denser to rarer medium and i > iC (3) light moves from rarer to denser medium and i < iC (4) light moves from denser to rarer medium and i < iC Sol: Ans [2] 26. Source of sound and observer are moving towards each other, the observer will hear (1) high frequency, high wavelength

(2) low frequency, low wavelength

(3) high frequency, low wavelength

(4) low frequency, high wavelength

Sol: Ans [3] 27. When a waves enters in a medium which does not change (1) frequency

(2) wavelength

(3) velocity

(4) amplitude

(2) Nibble

(3) Bit

(4) none of these

Sol: Ans [1] 28. Group of 8 bits is called (1) Byte Sol: Ans [2] 29. If output in a logic gate is low for atleast one input to be high (1) AND gate

(2) OR gate

(3) NOR gate

(4) NAND gate

Sol: Ans [3]

Amity Institute for Competitive Examinations : Phones: 24336143/44, 25573111/2/3/4, 95120-2431839/42 -4-

DPMT-2007

Physics

30. Air bubble in water behaves as (1) sometimes concave, sometimes convex lens

(2) concave lens

(3) convex lens

(4) always refracting surface

Sol: Ans [2] 31. It is given n e = 7 × 1011 per meter3 and n h = 5 × 1012 per meter3 . The semiconductor is (1) p type

(2) intrinsic

(3) n type

(4) insulator

Sol: Ans [1] 32. A hollow spherical pendulum field with mercury has time period T if mercury is thrown out completely then the new time period (1) increases

(2) decreases

(3) same

(4) none of these

Sol: Ans [3] 33. If number of nucleon increase, then binding energy per nucleon of the nucleus (1) first increases and then decreases with mass number (2) continuously increases with mass number (3) continuously decreases with mass number (4) remains constant with mass number Sol: Ans [1] B

34.

A

D

Sun C

Then maximum rotational kinetic energy of a planet moving around the Sun is at position (1) A

(2) B

(3) D

(4) C

Sol: Ans [3] 35. A particle is moving with constant acceleration then the correct graph is (V velocity, y displacement and t time) y

V

a

(1)

(2) t

V

(3) t

(4) t

Sol: Ans [3]

Amity Institute for Competitive Examinations : Phones: 24336143/44, 25573111/2/3/4, 95120-2431839/42 -5-

t

Physics

DPMT-2007

36. For a car not to turn safely on a curved road (1) speed is slow

(2) distance between tyres is large

(3) centre of gravity for car is low

(4) high friction force

Sol: Ans [4] 37. For beats to be produced (1) frequency of sources should be different and amplitude should be same (2) frequency of sources should be same and amplitude should be different (3) frequency of sources should be different and amplitude should be different (4) frequency of sources should be same and amplitude should be same Sol: Ans [1] 38. Find the temperature which is same in Celsius and Fahrenheit scale (1) 40° C

(2) – 40°C

(3) 80° C

(4) –80°C

Sol: Ans [2] 39. If the orbital radius of the earth is made 4 times then find the duration of the year if earlier it was T (1) T

(2) 2T

(3) 4T

(4) 8T

Sol: Ans [4] 40. If the resistance of the wire is made four times keeping potential difference across it constant then the number of times heat produced in it varies by (1) 4

(2) 1/4

(3) 2

(4) 1/2

Sol: Ans [2] 41. If for a heat engine temperature of the sink is 50°C and its efficiency is 50% then temperature of the source is (1) 273°C

(2) 373°C

(3) 100°C

(4) 200°C

(3) 12

(4) 6

Sol: Ans [2] 42. Coordination number for BCC crystal is (1) 4

(2) 8

Sol: Ans [2] 43. Which of the following is true regarding projectile motion (1) horizontal velocity of projectile is constant

(2) vertical velocity of projectile is constant

(3) acceleration is not constant

(4) momentum is constant

Sol: Ans [1]

bacd Amity Institute for Competitive Examinations : Phones: 24336143/44, 25573111/2/3/4, 95120-2431839/42 -6-