## Sunday, October 11, 2009

### IIT JEE Physics Final Revision Set 21

1. Two litre of water at initial temperature of 27° C is heated by a heater of power 1 kW. If the lid of kettle is opened, then heat is lost at the constant rate of 160 J/s. Find the time required to raise the temperature of water to 77° C with the lid open (Specific heat of water 4.2 kJ/kg)

(A) 5 min 40 sec (B) 14 min 20 sec
(C) 8 min 20 sec (D) 16 min 10 sec

2. Ideal gas is contained in a thermally insulated and rigid container and it is heated through a resistance 100Ω by
passing a current of 1A for five minutes, then change in internal energy of the gas is
(A) 0 kJ (B) 30 kJ
(C) 10 kJ (D) 20 kJ

Source: JEE screening 2005

3. Consider the spectral line resulting from the transition n=2 → n=1 in the atoms and ions given below. The shortest wave length is produced by

a. hydrogen atom
b. singly ionized helium
c. deuterium atom
d. doubly ionized lithium

4. State true or false
A beam of white light passing through a hollow prism gives no spectrum

5. State true or false
A charged particle enters a region of uniform magnetic fieldat an angle of 85°C to the magnetic lines of force. The path of the particle is circle.

Source: 1983 JEE paper