MCQ-6

26. A body weighs 250 N on the surface of the earth. How much will it weigh half way down to the centre of the earth ?

     (1) 125 N             (2) 200 N

     (3) 250 N             (4) 100 N

27. Six similar bulbs are connected as shown in the figure with a DC source of emf E and zero internal resistance.

 The ratio of power consumption by the bulbs when

(i) all are glowing and

(ii) in the situation when two from section A and one from    section B are glowing, will be :

      (1) 4 : 9                (2) 9 : 4

      (3) 1 : 2                (4) 2 : 1

28. For a p-type semiconductor, which of the following statements is true ?

     (1) Electrons are the majority carriers and trivalent atoms are the dopants.

     (2) Holes are the majority carriers and trivalent atoms are the dopants.

     (3) Holes are the majority carriers and pentavalent atoms are the dopants.

     (4) Electrons are the majority carriers and pentavalent atoms are the dopants.

29. Average velocity of a particle executing SHM in one complete vibration is :

 (1) Aw/2

     (2) Aw

     (3) Aw^2/2

     (4) Zero

30. The unit of thermal conductivity is :

(1) J m K–1                     (2) J m–1 K–1

(3) W m K–1                    (4) W m–1 K–1

EXPLANATION:

26) Answer:(1)

27) Answer:(1)

28) Answer:(2)

 In p-type semiconductor, an intrinsic

semiconductor is doped with trivalent

impurities, that creates deficiencies of

valence electrons called holes which are

majority charge carriers.

29) Answer:(4)

30) Answer:(4)