PHYSICS

PAPER – 1

(THEORY)

Section A

Answer all questions.

Question 1

(A) Choose the correct alternative (a), (b),(c) or (d)for each of the questions given below: [5×1]
(i) Ohm‟s law in vector form is:
(a) V = I.R
(b) J =  E
(c) J =  E
(d) E=  J
(ii) Current flowing through a long solenoid is varied. Then, magnetic flux density of the magnetic field inside it varies:
(a) inversely with I
(b) inversely with I2
(c) directly with I
(d) directly with I2
(iii) A convex lens, made of glass, is immersed in water. As a result, its focal length will:
(a) increase
(b) decrease
(c) double
(d) remain same
(iv) de Broglie wavelength of a moving particle is . Its momentum is given by:
(v) Half Life of a certain radioactive substance is 69·3 days. Its disintegration constant is:
(a) 0.010 day-1
(b) 0.100 day-1
(c) 0.001 day-1
(d) 1.00 day-1

(B) Answer the following questions briefly and to the point: [7×1]
(i) How will the sensitivity of a potentiometer change with increase in current flowing through its wire?
(ii) Which of the two; an ammeter or a voltmeter, has a greater resistance?
(iii) Why is soft iron preferred to steel in making the core of a transformer?
(iv) When would a moving charged particle travel undeviated in a uniform magnetic field?
(v) Complete the ray diagram shown in Figure 1, given that the critical angle for air-glass pair is ic=42o .

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