48. A capacitor is charged using an external battery with a resistance x in series. The dashed line shows the variation of ln I with respect to time. If the resistance is changed to 2x, the new graph will be

a) P b) Q

c) R d) S

Ans : b)

is inversely proportional to x.

49. A 280 days old radioactive substance shows an activity of 6000 dps, 140 days later it's activity becomes 3000 dps. What was its initial activity ?

a) 20000 dps b) 24000 dps

c) 12000 dps d) 6000 dps

Ans : b)

, and

50. Two identical rods are connected between two containers one of them is at and another is at . If rods are connected in parallel then the rate of melting of ice gm/sec. If they are connected in series then rate is . Then the ratio is

a) 2 b) 4

c) 1/2 d) 1/4

Ans: d)

and

51. A particle starts sliding down a frictionless inclined plane. If is the distance travelled by it from time sec, the ratio is

a) b)

c) d)

Ans : a)

52. A small bar magnet is being slowly inserted with constant velocity inside a solenoid as in fig. Which graph best represents the relationship between emf induced with time

a) b)

c) d)

Ans :c)

53. A point object is placed at the centre of a glass sphere of radius 6 cm and refractive index 1.5. The distance of virtual image from the surface is

a) 6 cm b) 4 cm

c) 12 cm d) 9 cm

Ans : a)

Object is at centre of curvature, hence image will also be at centre of curvature.

54. A proton has kinetic energy E = 100keV which is equal to that of a photon. The wavelength of photon is and that of proton is . The ratio of is proportional to

a) b)

c) d)

Ans :b)