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# IIT-JEE-Physics-Paper1-2007

## Paper 1

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1.     A resistance of 2 W is connected across one gap of a meter-bridge (the length of the wire is 100 cm) and an unknown resistance, greater than 2W, is connected across the other gap. When the resistances are interchanged, the balance point shifts by 20 cm. neglecting any corrections, the unknown resistance is

(A)    3Ω

(b)    4Ω

(C)    5Ω

(D)    6Ω

2.     In an experiment to determine the focal length (f) of a concave mirror by the n-v method, a student places the object pin A or the principal axis at a distance x from the pole P. The student looks at the pin and its inverted image from a distance keeping his/her eye in line with PA. When the student shifts his/her eye towards left, the image appears to the right of the object pin. Then,

(A)    x < f

(B)    f < x < 2f

(C)    x = 2f

(D)    x > 2f

3.     Two particles of mass m each are tied at the ends of a light string of length 2a. The whole system is kept on a frictionless horizontal surface with the string held tight so that each mass is at a distance 'a' from the center P (as shown in the figure). Now, the mid-point of the string is pulled vertically upwards with a small but constant for F. As a result, the particles move towards each other on the surface. The magnitudes of acceleration, when the separation between them becomes 2x, is

(A) F/2m a/√(a2 - x2 )

(B) F/2m x/√(a2 - x2 )

(C) F/2m x/a

(D) F/2m √(a2 - x2 )/x

4.     A long, hollow conducting cylinder is kept coaxially inside another long, hollow conducting cylinder of larger radius. Both the cylinders are initially electrically neutral.

(A)    A potential difference appears between the two cylinders when a charge density is given to the inner cylinder.

(B)    A potential difference appears between the two cylinders when a charge density is given to the outer cylinder

(C)    No potential difference appears between the two cylinders when a uniform line charge is kept along the axis of the cylinders

(D)    No potential difference appears between the two cylinders when a same charge density is given to both the cylinders

5.     Consider a neutral conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then,

(A)    negative and distributed uniformly over the surface of the sphere

(B)    negative and appears only at the point on the sphere closest to the point charge

(C)    negative and distributed non-uniformly over the entire surface of the sphere

(D)    zero

6.     A circuit is connected as shown in the figure with the switch S open. When the switch is closed, the total amount of charge that flows from Y to X is

(A)    0

(B)    54 µC

(C)    27 µC

(D)    81 µC

7.     A ray of light traveling in water is incident on its surface open to air. The angle of incidence is, which is less than the critical angle. Then there will be

(A)    only a reflected ray and no refracted ray

(B)    only a refracted ray and no reflected ray

(C)    a reflected ray and a refracted ray and the angle between them would be less than 180o - 2θ

(D)    a reflected ray and a refracted ray and the angle between them would be greater than 180o - 2θ

8.     In the options given below, let E denote the rest mass energy of a nucleus and n a neutron. The correct option is

(A) E(236U92) > E(137I53) + E(97Y39) + 2E(n)

(B) E(236U92) < E(137I53) + E(97Y39) + 2E(n)

(C) E(236U92) < E(140Ba56) + E(94Kr36) + 2E(n)

(D) E(236U92) = E(140Ba56) + E(94Kr36) + 2E(n)

9.     The largest wavelength in the ultraviolet region of the hydrogen spectrum is 122 nm. The smallest wavelength in the infrared region of the hydrogen spectrum to the nearest integer) is

(A)    802 nm

(B)    823 nm

(C)    1882 nm

(D)    1648 nm