All India Pre-Medical / Pre-Dental Entrance Examination

CBSE Guess > AIPMT > AIPMT 2007 Screening > Physics

AIPMT 2007 Physics Screening

Q. 21. The electric and magnetic field of an electromagnetic wave are

1. in phase and perpendicular to each other
2. in phase and parallel to each other
3. in opposite phase and perpendicular to each other
4. in opposite phase and parallel to each other

Sol.

Correct choice: (1)

Q. 22. A small coin is resting on the bottom of a beaker filled with a liquid. A ray of light from the coin travels upto the surface of the liquid and moves along its surface (see figure). How fast is the light traveling in the liquid?

Sol . Correct choice: (2)

Q. 23. Charges +q and -q are placed at points A and B respectively which are a distance 2L apart, C is the midpoint between A and B. The work done in moving a charge +Q along the semicircle CRD is

Sol. At C potential

Correct choice: (1)

Q. 24. A hollow cylinder has a charge q coulomb within it. If f is the electric flux in units of volt × meter associated with the curved surface B, the flux linked with the plane surface A in units of volt × meter will be

Sol. Correct choice: (2)

Q. 25. Three point charges +q, - 2q and +q are placed at points (x = 0, y = a, z = 0), (x = 0, y = 0, z = 0) and (x = a, y = 0, z = 0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are

Sol . Correct choice: (3)

Q. 26. Two condensers, one of capacity C and the other of capacity C/2, are connected to a V-volt battery, as shown. The work done in charging fully both the condensers is

Sol. Correct choice: (4)

Q. 27. The total power dissipated in Watts in the circuit shown here is

1. 4
2. 16
3. 40
4. 54

Sol . Correct choice: (4)

Q. 28. A steady current of 1.5 amp flows through a copper voltameter for 10 minute. If the electrochemical equivalent of copper is 30´10 ^-5 gm coulomb^-1 , the mass of copper deposited on the electrode will be

1. 0.27 gm
2. 0.40 gm
3. 0.50 gm
4. 0.67 gm

Sol . m = Zit; m = 0.27gm Correct choice: (1)

Q. 29. If the cold junction of a thermo-couple is kept at 0⁰C and the hot junction is kept at T⁰C, then the relation between neutral temperature (Tn ) and temperature of inversion (Ti ) is

Sol . Correct choice: (2)

Q. 30. Three resistances P, Q, R each of and an unknown resistance S form the four arms of a Wheatstone bridge circuit. When a resistance of is connected in parallel to S the bridge gets balanced. What is the value of S?

Sol .

Correct choice: (3)

Q. 31. The resistance of an ammeter is and its scale is graduated for a current upto 100 Amps. After an additional shunt has been connected to this ammeter it becomes possible to measure currents upto 750 Amperes by this meter. The value of shunt-resistance is

Sol.

Correct choice: (3)

Q. 32. Under the influence of a uniform magnetic field a charge-particle is moving in a circle of radius R with constant speed V. The time period of the motion

1. depends on R and not on V
2. depends on V and not on R
3. depends on both R and V
4. is independent of both R and V

Sol. Correct choice: (4)

Q. 33. A charged particle (charge q ) is moving in a circle of radius R with uniform speed v . The associated magnetic moment is given by

1. qvR
2. qv R / 2
3. qv R²
4. qvR² / 2

Sol. Correct choice: (2)

Q. 33. A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move

1. along a straight line
2. in an elliptical orbit
3. in a circular orbit
4. along a parabolic path

Sol. As velocity, magnetic field and electric field are mutually perpendicular. Correct choice: (3)

Q. 34. A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move

1. along a straight line
2. in an elliptical orbit
3. in a circular orbit
4. along a parabolic path

Sol. As velocity, magnetic field and electric field are mutually perpendicular. Correct choice: (3)

Q. 35. The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flu f linked with the primary coil is given by is a constant, the output voltage across the secondary coil is

1. 30 volts
2. 90 volts
3. 120 volts
4. 220 volts

Sol. Correct choice: (3)

Q. 36. What is the value of inductance L for which the current is a maximum in a series LCR circuit with

1. 10 mH
2. 100 mH
3. 1 mH
4. cannot be calculated unless R is known

Sol. Correct choice: (2)

Q. 37. A transformer is used to light a 100W and 110V lamp from a 220V mains. If the main current is 0.5A, the efficiency of the transformer is approximately

1. 10%
2. 30%
3. 50%
4. 90%

Sol. Correct choice: (4)

Q. 38. Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature then it will show

1. diamagnetism
2. paramagnetism
3. anti ferromagnetism
4. no magnetic property

Sol . Fact based Correct choice: (2)

Q. 39. A 5 watt source emits monochromatic light of wavelength . When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0 m, the number of photoelectrons liberated will

1. be reduced by a factor of 2
2. be reduced by a factor of 4
3. be reduced by a factor of 8
4. be reduced by a factor of 16

Q. 40. Monochromatic light of frequency is produced by a laser. The power emitted is . The number of photons emitted, on the average, by the source per second is

Sol . Correct choice: (2)