Assertion:  Current is passed through a metallic wire so that it becomes red hot. When cold water is poured on half of its portion, the rest of the half portion becomes more hot. 

Reason:  Resistance decreases due to decrease in temperature.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

142.

1 g of steam is sent into 1 g of ice. At thermal equilibrium, the resultant temperature of mixture is

• 270^oC

• 230^oC

• 100^oC

• 120^oC

Assertion:  Water kept in an open vessel will quickly evaporate on the surface of the moon. 

Reason:  The temperature at the surface of the moon is much higher than the boiling point of water.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Dimensional formula of ΔQ, heat supplied to the system is given by

• [ M¹ L² T^-2 ]

• [ M¹ L¹ T^-2 ]

• [ M¹ L² T^-1 ]

• [M¹ L¹ T^-1 ]

Two conductors having same width and length, thickness d₁ and d₂ thermal conductivity K₁ and K₂ are placed one above the another. Find the equivalent thermal conductivity.

• $\frac{\left({\mathrm{d}}_1+ {\mathrm{d}}_2\right) \left({\mathrm{K}}_1 {\mathrm{d}}_2 + {\mathrm{K}}_2 {\mathrm{d}}_1\right)}{2 \left({\mathrm{K}}_1 + {\mathrm{K}}_2\right)}$

• $\frac{\left({\mathrm{d}}_1 - {\mathrm{d}}_2\right) \left({\mathrm{K}}_1 {\mathrm{d}}_2 + {\mathrm{K}}_2 {\mathrm{d}}_1\right)}{2 \left({\mathrm{K}}_1 + {\mathrm{K}}_2\right)}$

• $\frac{{\mathrm{K}}_1 {\mathrm{d}}_1 + {\mathrm{K}}_2 {\mathrm{d}}_2}{{\mathrm{d}}_1 + {\mathrm{d}}_2}$

• $\frac{{\mathrm{K}}_1 + {\mathrm{K}}_2}{{\mathrm{d}}_{1_{ }}+ {\mathrm{d}}_2}$

Assertion:  Maximum air flow due to convection does not occur at the north pole but it occurs at 30°N. 

Reason: There is maximum temperature difference between equator and 30° N.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Emissive and absorptive power of a material at 2000 K is 8 and 10 respectively, calculate the emissivity of IBB (Ideal black body)

• 0.2

• 0.4

• 0.6

• 0.8

Assertion: C_P is always greater than C_V in gases.

Reason: Work done at constant pressure is more than at constant volume

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

When a current is passed in a conductor, 3^o C rise in temperature is observed. If the strength of current is made thrice, then rise in temperature will approximately be

• 36^oC

• 27^o C

• 18^o C

• 9^o C

In  a  metal  with  positive  Thomson  coefficient, current is  passed  from  the  lower  temperature  to  higher   temperature  to  higher  temperature  side. The  heat  will   be

• absorbed

• constant

• evolved

• either 'b' or 'c'