## Monday, October 12, 2009

### IIT JEE Physics Final Revision Set 32

1. STATEMENT -1
In a Meter Bridge experiment, null point for an unknown resistance is measured. Now, the unknown
resistance is put inside an enclosure maintained at a higher temperature. The null point can be obtained at
the same point as before by decreasing the value of the standard resistance.
and
STATEMENT-2
Resistance of a metal increases with increase in temperature.
(A) STATEMENT – 1 is True, STATEMENT- 2 is True; STATEMENT -2 is a correct explanation for
STATEMENT -1
(B) STATEMENT – 1 is True, STATEMENT- 2 is True; STATEMENT -2 is NOT a correct explanation
for STATEMENT -1
(C) STATEMENT-1 is True, STATEMENT-2 is False
(D) STATEMENT-1 is False, STATEMENT-2 is True

2. STATEMENT – 1
Two cylinders, one hollow (metal) and the other solid (wood) with the same mass and identical
dimensions are simultaneously allowed to roll without slipping down an inclined plane from the same
height. The hollow cylinder will reach the bottom of the inclined plane first.
and
STATEMENT – 2
By the principle of conservation of energy, the total kinetic energies of both the cylinders are identical
when they reach the bottom of the incline.
(A) STATEMENT – 1 is True, STATEMENT- 2 is True; STATEMENT -2 is a correct explanation for
STATEMENT -1
(B) STATEMENT – 1 is True, STATEMENT- 2 is True; STATEMENT -2 is NOT a correct explanation
for STATEMENT -1
(C) STATEMENT-1 is True, STATEMENT-2 is False
(D) STATEMENT-1 is False, STATEMENT-2 is True

3. STATEMENT – 1
The stream of water flowing at high speed from a garden hose pipe tends to spread like a fountain when
held vertically up, but tends to narrow down when held vertically down.
and
STATEMENT – 2
In any steady flow of an incompressible fluid, the volume flow rate of the fluid remains constant.
(A) STATEMENT – 1 is True, STATEMENT- 2 is True; STATEMENT -2 is a correct explanation for
STATEMENT -1
(B) STATEMENT – 1 is True, STATEMENT- 2 is True; STATEMENT -2 is NOT a correct explanation for STATEMENT -1
(C) STATEMENT-1 is True, STATEMENT-2 is False
(D) STATEMENT-1 is False, STATEMENT-2 is True

Paragraph
In a mixture of H and He+ gas (He+ is singly ionized He atom), H atoms and He+ ions are excited to their respective first excited states. Subsequently, H atoms transfer their total excitation energy to He+ ions (by collisions). Assume that the Bohr model of atom is exactly valid.

4. The quantum number n of the state finally populated in He+ ions is
(A) 2 (B) 3 (C) 4 (D) 5

5. The wavelength of light emitted in the visible region by He+ ions after collisions with H atoms is
(A) 6.5 × 10-7 m (B) 5.6 × 10-7 m
(C) 4.8 × 10-7 m (D) 4.0 × 10-7 m

6. The ratio of the kinetic energy of the n = 2 electron for the H atom to that of He+ ion is

a. 1/4 b. 1/2 c. 1 d. 2