Nsep

An isolated metallic object is charged in vacuum to a potential V₀ using a suitable source, its electrostatic energy being W₀. It is then disconnected from the source and immersed in a large volume of dielectric with dielectric constant K. The electrostatic energy of the sphere in the dielectric is :

(A)  K²W₀

(B)   K W₀

(C)   W_0/K²

(D)  W₀/K

An object is placed 30 cm away from a symmetric convex lens and an image two thirds of the size of the object is produced. The object is moved by a distance of 20 cm so as to get a magnified image. Now we get 

(a)  a real image of magnification 

(b)  a virtual image of magnification 5 

(c)  a real image at a distance of 40 cm 

(d)  a virtual image at a distance of 60 cm

If the threshold of hearing is assumed to be the reference (0 dB), then the threshold of pain is taken to be 120 dB. Let the corresponding sound intensities be I₀ and I respectively. Then I₀/I is

(a) 120 (b) 10¹² (c) 10^-12 (d) 10^1.2 

The variation of amplitude A with respect to time t is shown as

Refer to the circuit given below. Output voltage V₀ is measured between points a and b. Then,

(a)  the peak value of V₀ is 2.5 V above the minimum if the diode is assumed to be ideal 

(b)  the positive half cycle of the input is clipped 

(c)  the circuit acts as a rectifier 

(d)  the peak value V₀ is about 3.2 V above the minimum if D is silicon diode (non-ideal)

Which of the following will give a straight line graph? 

(a) log A against t (b) log A against1/t (c) A against t² (d) A² against t

A convex lens and concave lens are kept in contact and the combination is used for the formation of image of a body by keeping it at different places on the principal axis. The image formed by this combination of lenses can be : 

(A) Magnified, inverted and real

(B)  Diminished, inverted and real

(C) Diminished, erect and virtual

(D) Magnified, erect and virtual 

The frequency of the pendulum having maximum amplitude is 

(a)  f₀ / 2 

(b)  f₀ 

(c)   2 f₀ 

(d)  not related to  f₀

It is claimed that the strips S and S¹ serve two purposes I. to decide the end points of the wire and II. To keep the wires in place, then 

(a)  both I and II are important 

(b)  I is more important than II 

(c)  II is more important than I 

(d)  both are equally important

A ball is dropped onto a horizontal surface from a height of 36 cm. After bouncing several times it comes to rest covering a total distance of 100 cm measured in a vertical direction. The percentage loss in its kinetic energy after its first impact is

(a) 36 (b) 64 (c) 53 (d) 96