ISC Board Class 12 Physics Sample Paper 2024-25: Download Sample Paper PDF With Answer Key!

Question 1

(A)

In questions (i) to (vii) below, choose the correct alternative (a), (b), (c) or (d) for each of the questions given below:

(i)

Figure 1 below shows a circuit containing an ammeter A, a galvanometer G and a plug key K. When the key is closed:

[1]

(a)

both G and A show deflections.

(b)

neither G nor A shows deflection.

(c)

G shows deflection but A does not.

(d)

A shows deflection but G does not.

(ii)

A circular coil having N turns of radius R carrying a current I is used to produce a magnetic field B at its centre O. If this coil is opened and rewound such that the radius of the newly formed coil is 2R, carrying the same current I, what will be the magnetic field at the centre O? (Analysis)

[1]

(a)

2B

(b)

B

(c)

B/2

(d)

B/4

(iii)

Magnetic susceptibility of a diamagnetic substance: (Recall)

[1]

(a)

decreases with the increase in its temperature.

(b)

is not affected by the change in temperature.

(c)

increases with an increase in its temperature.

(d)

first increases then decreases with an increase in its temperature.

(iv)

The de Broglie wavelength of an electron in the first Bohr’s orbit of a hydrogen

atom is equal to: (Understanding)

[1]

(a)

diameter of the first orbit.

(b)

circumference of the first orbit.

(c)

radius of the second orbit.

(d)

h/2π.

(v)

An ideal PN junction diode offers: (Recall)

[1]

(a)

zero resistance in forward as well as reverse bias.

(b)

infinite resistance in forward as well as reverse bias.

(c)

zero resistance in forward, but infinite resistance in reverse bias.

(d)

infinite resistance in forward, but zero resistance in reverse bias.

(vi)

Given below are two statements marked Assertion and Reason. Read the two statements and choose the correct option.

Assertion: An astronomical telescope has an objective lens with having large focal length.

Reason: The magnifying power of an astronomical telescope varies directly with the focal length of the objective lens. (Understanding)

[1]

(a)

Both Assertion and Reason are true and Reason is the correct explanation for Assertion.

(b)

Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.

(c)

Assertion is false and Reason is true.

(d)

Both Assertion and Reason are false.

(vii)

Given below are two statements marked, Assertion and Reason. Read the two statements and choose the correct option.

Assertion: If the critical angle of the glass-air pair (μg = 3/2) is θ1 and that of the water-air pair (μw = 4/3) is θ2, then the critical angle for the water-glass pair will lie between θ1 and θ2.

Reason: A medium is optically denser if its refractive index is greater.

(Analysis)

[1]

(a)

Both Assertion and Reason are true and Reason is the correct explanation for Assertion.

(b)

Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.

(c)

Assertion is false and Reason is true.

(d)

Both Assertion and Reason are false.

(B)

Answer the following questions briefly:

(i)

Current I flowing through a metallic wire is gradually increased. Show graphically how heating power (P) developed in it varies with the current (I). (Application)

[1]

(ii)

Explain why the core of a transformer is always laminated.

(Recall)

[1]

(iii)

Why does a car driver use a convex mirror as a rear-view mirror?

(Recall)

[1]

(iv)

Represent diagrammatically how the incident planar wavefronts of wavelength λ pass through an aperture of size d, when d is approximately equal to λ. (Understanding)

[1]

(v)

What is meant by “Dual nature of matter”?

(Recall)

[1]

(vi)

What happens when an electron collides with a positron?

(Recall)

[1]

(vii)

What energy conversion takes place in a solar cell?

(Recall)