Model Paper 2 — Physics STD 12 Science — Question

Match the List I with the List II from the combinations shown

(I)	Presbiopia	(A)	Sphero-cylindrical lens
(II)	Hypermetropia	(B)	Convex lens of proper power may be used close to the eye
(III)	Astigmatism	(C)	Concave lens of suitable focal length
(IV)	Myopia	(D)	Bifocal lens of suitable focal length

(a) I-A; II-C; III-B; IV-D

(b) I-B; II-D; III-C; IV-A

(c) I-D; II-B; III-A; IV-C

(d) I-D; II-A; III-C; IV-B

An aeroplane in which the distance between the tips of wings is 50 m is flying horizontally with a speed of 360 km/hr over a place where the vertical components of earth magnetic field is 2.0 . The potential difference between the tips of wings would be

(a) 0.1 V

(b) 1.0 V

(c) 0.2 V

(d) 0.01 V

Dynamo core is laminated because

(a) Magnetic field increases

(b) Magnetic saturation level in core increases

(c) Residual magnetism in core decreases

(d) Loss of energy in core due to eddy currents decreases

A radioactive material undergoes decay by ejecting electrons. The electron ejected in this process is:

The turn ratio of a transformers is given as 2 : 3. If the current through the primary coil is 3 A, thus calculate the current through load resistance

(a) 1 A

(b) 4.5 A

(c) 2 A

(d) 1. 5 A

Consider an electron in the n^th orbit of a hydrogen atom in the Bohr model. The circumference of the orbit can be expressed in terms of the de Broglie wavelength λ of that electron as

(a) (0.259)n λ

(b)  λ

(c) (13.6) λ

(d) n λ

Assertion  : Amongst alpha, beta and gamma rays, a-particle has maximum penetrating power.

Reason      : The alpha particle is heavier than beta and gamma rays.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Inside a uniform spherical shell:

1. The gravitational potential is zero.
2. The gravitational field is zero.
3. The gravitational potential is same everywhere.
4. The gravitational field is same everywhere.

Figure shows a conducting loop being pulled out of a magnetic field with a speed u. Which of the four plots shown in figure may represent the power delivered by the pulling agent as a function of the speed u?