MCQ-9

41. A solid cylinder of mass 2 kg and radius 4 cm rotating about its axis at the rate of 3 rpm. The torque required to stop after 2p revolutions is

      (1) 2 × 10^–6 N m        (2) 2 × 10^–3 N m

      (3) 12 × 10^–4 N m      (4) 2 × 10^6 N m

42 . A force F = 20 + 10 y acts on a particle in y-direction where F is in newton and y in meter. Work done by this force to move the particle from y = 0 to y = 1 m is

      (1) 30 J                       (2) 5 J

      (3) 25 J                      (4) 20 J

43.Which of the following acts as a circuit protecting device?

      (1) Conductor

      (2) Inductor

      (3) Switch

      (4) Fuse

44.In the circuits shown below, the readings of

voltmeters and the ammeters will be

     (1) V2 > V1   and   i1 = i2

     (2) V1 = V2  and   i1 > i2

     (3) V1 = V2  and   i1 = i2

     (4) V2 > V1  and   i1 > i2

45. A hollow metal sphere of radius R is uniformly charged. The electric field due to the sphere at a distance r from the centre

(1)       Increases as r increases for r < R and for r > R

(2)     Zero as r increases for r < R, decreases as r increases for r > R

   (3)  Zero as r increases for r < R, increases as r increases for r > R

   (4) Decreases as r increases for r < R and for r > R

EXPLANATION:

41.Answer (1)

42.Answer (3)

43.Answer (4)

Fuse wire has less melting point so when

excess current flows, due to heat produced

in it, it melts.

44.Answer (3)

45.Answer (2)