NEET Physics - New - Thermal Properties of Matter

Question - 1

A spherical black body with a radius of 12 cm radiates 450 watt power at 500 K. If the radius were halved and the temperature doubled, the power radiated in watt would be____

• A 225
• B 450
• C 1000
• D 1800

Question - 2

The two ends of a metal rod are maintained at temperatures $100^{\circ} \mathrm{C}$ and $110^{\circ} \mathrm{C}$. The rate of heat flow in the rod is found to be $4.0 \mathrm{~J} / \mathrm{s}$. If the ends are maintained at temperatures $200^{\circ} \mathrm{C}$ and $210^{\circ} \mathrm{C}$, the rate of heat flow will be____

• A $16.8 \mathrm{~J} / \mathrm{s}$
• B $8.0 \mathrm{~J} / \mathrm{s}$
• C $4.0 \mathrm{~J} / \mathrm{s}$
• D $44.0 \mathrm{~J} / \mathrm{s}$

Question - 3

On observing light from three different stars P, Q and R, it was found that intensity of violet colour is maximum in the spectrum of P, the intensity of green colour is maximum in the spectrum of R and the intensity of red colour is maximum in the spectrum of Q. If $T_{P}, T_{Q}$ and $T_{R}$ are the respective absolute temperature of P, Q and R, then it can be concluded from the above observations that ___________ .

• A $T_{P}>T_{R}>T_{Q}$
• B $T_{P}<T_{R}<T_{Q}$
• C $T_{P}<T_{Q}<T_{R}$
• D $T_{P}>T_{Q}>T_{R}$

Question - 4

Certain quantity of water cools from $70^{\circ} \mathrm{C}$ to $60^{\circ} \mathrm{C}$ in the first 5 minutes and to $54^{\circ} \mathrm{C}$ in the next 5 minutes. The temperature of the surroundings is______

• A $45^{\circ} \mathrm{C}$
• B $20^{\circ} \mathrm{C}$
• C $42^{\circ} \mathrm{C}$
• D $10^{\circ} \mathrm{C}$

Question - 5

Steam at $100^{\circ} \mathrm{C}$ is passed into $20 \mathrm{~g}$ of water at $10^{\circ} \mathrm{C}$. When water acquires a temperature of $80^{\circ} \mathrm{C}$, the mass of water present will be:
[Take specific heat of water $=1 \mathrm{cal} \mathrm{g}^{-1}{ }^{\circ} \mathrm{C}^{-1}$ and latent heat of steam $=540 \mathrm{cal} \mathrm{g}^{-1}$ ]_____

• A $24 \mathrm{~g}$
• B $31.5 \mathrm{~g}$
• C $42.5 \mathrm{~g}$
• D $22.5 \mathrm{~g}$

Question - 6

Two metal rods 1 and 2 of same lengths have same temperature difference between their ends. Their thermal conductivities are K1 and K2 and cross sectional areas A1 and A2, respectively. If the rate of heat conduction in rod 1 is four times that in rod 2, then ______

• A $K_{1} A_{1}=K_{2} A_{2}$
• B $K_{1} A_{1}=4 K_{2} A_{2}$
• C $K_{1} A_{1}-2 \bar{K}_{2} A_{2}$
• D $4 K_{1} A_{1}=K_{2} A_{2}$

Question - 7

The density of water at 20o C is 998 kg / m3 and at 40o C is 992 kg / m3. The coefficient of volume expansion of water is_____.

• A $10^{-4 / \rho} \mathrm{C}$
• B $3 \times 10^{-4 / 0} \mathrm{C}$
• C $2 \times 10^{-4 / \rho} \mathrm{C}$
• D $6 \times 10^{-4 / 9} \mathrm{C}$

Question - 8

The molar specific heats of an ideal gas at constant pressure and volume are denoted by CP and CV respectively. If $Y=\frac{C_{P}}{C_{V}}$ and R is the universal gas constant, then CV is equal to_____

• A $\frac{R}{(y-1)}$
• B $\frac{(\gamma-1)}{R}$
• C $\mathrm{g} R$
• D $\frac{1+\gamma}{1-\gamma}$

Question - 9

A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using______

• A Wien's displacement law
• B Kirchoff's law
• C Newton's law of cooling
• D Stefan's law

Question - 10

A slab of stone of area $0.36 \mathrm{~m}^{2}$ and thickness $0.1 \mathrm{~m}$ is exposed on the lower surface to steam at $100^{\circ} \mathrm{C}, \mathrm{A}$ block of ice at $0^{\circ} \mathrm{C}$ rests on the upper surface of the slab. In one hour $4.8 \mathrm{~kg}$ of ice is melted. The thermal conductivity of slab is (Given latent heat of fusion of ice $=3.36 \times 10^{5} \mathrm{Jkg}^{-1}$)_____

• A $1.24 \mathrm{~J} / \mathrm{m} / \mathrm{s} /{ }^{\circ} \mathrm{C}$
• B $1.29 \mathrm{~J} / \mathrm{m} / \mathrm{s} /{ }^{\circ} \mathrm{C}$
• C $2.05 \mathrm{~J} / \mathrm{m} / \mathrm{s} /{ }^{\circ} \mathrm{C}$
• D $1.02 \mathrm{~J} / \mathrm{m} / \mathrm{s} /{ }^{6} \mathrm{C}$