JEE 2020: Weekly Quiz 8 (07.07.2019) for JEE & BITSAT Exams

Question 1

What will be the operating temperature of a tube-light of 120 W, if it supposed to be perfectly black body of area 2 cm²?

Question 2

A circular metallic ring of radius R has a small gap of width d. The coefficient of thermal expansion of the metal is

in appropriate units. If we increase the temperature of the fing by an amount ΔT , then width of the gap

Question 3

A cylindrical steel rod of length 0.10

and thermal conductivity 50

is welded end to end to copper rod of thermal conductivity 400

and of the same are of cross section but 0.20

long. The free end of the steel rod is maintained at 100

and that of the copper rod at 0

. Assuming that the rods are perfectly insulated from the surrounding the temperature at the junction of the two rods is

Question 4

Two rods, one made of copper and the other steel of the same length and cross-sectional area are joined together. (The thermal conductivity of copper is 385 Js^-1m^-1K^-1 and steel is 50 Js^-1m^-1K^-1.) If the copper end is held at 100

and the steel end is held at 0

, what is the junction temperature (assuming no other heat losses)?

Question 5

A new temperature scale uses X as a unit of temperature, where the numerical value of the temperature t_{x ,} in this scale is related to the absolute temperature T by t_x-3T+300. If the specific heat of a material using this unit is 1400 J kg^-1X^-1 is specific heat in the S.I System of units is

Question 6

Two bottles

and

have radii

and

and heights

and

respectively with

and

These are filled with hot water at C. Consider that heat loss for the bottles takes place only from side surfaces. If the time the water takes to cool down to C is

and

for bottles A and B, respectively, then

and

are best related as,

Question 7

A black rectangular surface of area 'A' emits energy 'E' per second at 27 °C. If length and breadth are reduced to

of initial value and temperature is raised to 327 °C then 3 energy emitted per second becomes

Question 8

The thermo emf of a thermocouple varies with the temperature θ of the hot junction as E = a θ + bθ² in volts where the ratio a/b is 700 °C. If the cold junction is kept at 0°C, then the neutral temperature is

Question 9

A battery is charged at a potential of 15 V in 8 h when the current flowing is 10A. The battery on discharge supplies a current of 5A for 15 h. The mean terminal voltage during discharge is 14V. The watt-hour efficiency of battery is

Question 10

Which has more luminous efficiency?

Question 11

If the kinetic energy of an electron is increased four times, the wavelength of the de-Broglie wave associated with it would become

Question 12

Among the following which is the best description of water in the solid phase?

Question 13

According to Raoult’s law the relative decrease in solvent vapor pressure over the solution is equal to
(i) mole fraction of solvent
(ii) mole fraction of solute
(iii) no of moles of solute
(iv) none of these
Choose the CORRECT option

Question 14

TAB is a boiling point of solution of two liquids A and B. The binary solution shows negative deviation from Raoult's law. Hence, correct relation of TAB, TA and TB is

Question 15

Maximum deviation from ideal gas is expected from :

Question 16

A

mixture of helium and methane is contained in a vessel at 10 bar pressure. Due to a hole in the vessel, the gas mixture leaks out. The composition of the mixture effusing out initially is :