Three rods of Copper, Brass and Steel are welded together to from a Y –shaped structure. Area of cross – section of each rod = 4 cm². End of the copper rod is maintained at 100^oC where as ends of brass and steel are kept at 0^oC. Lengths of the copper, brass and steel rods are 46, 13 and 12 cms respectively. The rods are thermally insulated from surroundings except at ends. Thermal conductivities of copper, brass and steel are 0.92, 0.26 and 0.12 CGS units respectively. Rate of heat flow through copper rod is:

• 1.2 cal/s

• 2.4 cal/s

• 4.8 cal/s

• 4.8 cal/s

One mole of diatomic ideal gas undergoes a cyclic process ABC as shown in the figure. The process BC is adiabatic. The temperatures at A, B and C are 400 K, 800 K and 600 K respectively. Choose the correct statement:

• The change in internal energy in the process AB is -350 R.

• The change in internal energy in the process BC is -500 R.

• The change in internal energy in the whole cyclic process is 250 R.

• The change in internal energy in the whole cyclic process is 250 R.

An open glass tube is immersed in mercury in such a way that a length of 8 cm extends above the mercury level. The open end of the tube is then closed and sealed and the tube is raised vertically up by additional 46 cm. What will be the length of the air column above mercury in the tube now? (Atmospheric pressure = 76 cm of Hg)

• 16 cm

• 22 cm

• 38 cm

• 38 cm

A particle moves with simple harmonic motion in a straight line. In first τ s, after starting from rest it travels a distance a, and in next τ s it travels 2a, in the same direction, then

• amplitude of motion is 3a

• time period of oscillations is 8τ

• amplitude of motion is 4a

• amplitude of motion is 4a

A pipe of length 85 cm is closed from one end. Find the number of possible natural oscillations of the air column in the pipe whose frequencies lie below 1250 Hz. The velocity of sound in air is 340 m/s.

• 12

• 8

• 6

• 6

Match List-I (Electromagnetic wave type) with List-II (Its association/application) and select the correct option from the choices given below the lists:

• A	B	C	D
  4	3	2	1

• A	B	C	D
  1	2	4	3

• A	B	C	D
  3	2	1	4

• A	B	C	D
  3	2	1	4

The current voltage relation of the diode is given by I = e(1000V/T-1) mA, where the applied voltage V is in volt and the temperature T is in kelvin. If a student makes an error measuring ± 0.01V while measuring the current of 5mA at 300K, what will be the error in the value of current in mA?

• 0.2 mA

• 0.02 mA

• 05 mA

• 05 mA

18.

Assume that an electric field  exists in space. Then the potential difference V_A – V_O, where VO is the potential at the origin and V_A the potential at x = 2 m is:

• 120 J

• -120 J

• -80 J

• -80 J

A parallel plate capacitor is made of two circular plates separated by a distance of 5 mm and with a dielectric of dielectric constant 2.2 between them. When the electric field in the dielectric is 3 × 104 V/m, the charge density of the positive plate will be close to

• 6 x 10^-7 C/m²

• 3  x 10^-7 C/m²

• 3 x 10⁴ C/m²

• 3 x 10⁴ C/m²

In a large building, there are 15 bulbs of 40 W, 5 bulbs of 100 W, 5 fans of 80 W and 1 heater of 1kW. The voltage of the electric mains is 220 V. The minimum capacity of the main fuse of the building will be

• 8 A

• 10 A

• 12 A

• 12 A