# A temperature of $$100^{\circ}\text {F}$$ (Fahrenheit scale) is equal to $$T~\text{K}$$ (Kelvin scale). The value of $$T$$ is: 1. $$310.9$$ 2. $$37.8$$ 3. $$100$$ 4. $$122.4$$

Subtopic:  Temperature and Heat |
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A body cools down from $$80^{\circ}\mathrm{C}$$ $\mathrm{to}$ $$70^{\circ}\mathrm{C}$$ in 5 minutes. The temperature of the same body will fall from $$70^{\circ}\mathrm{C}$$$\mathrm{}$ $\mathrm{to}$ $$60^{\circ}\mathrm{C}$$$\mathrm{}$ in:

 1 less than 5 minutes. 2 equal to 5 minutes. 3 more than 5 minutes. 4 can't say anything as the temperature of the surroundings is not known.

Subtopic:  Newton's Law of Cooling |
62%
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If ${\lambda }_{m}$ is the wavelength, corresponding to which the radiant intensity of a block is at its maximum and its absolute temperature is T, then which of the following graph correctly represents the variation of T?

 1 2 3 4

Subtopic:  Wien's Displacement Law |
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A pendulum clock runs faster by 5 seconds per day at $$20^{\circ}\mathrm {C}$$ and goes slow by 10 second per day at $$35^{\circ}\mathrm {C}$$. It shows the correct time at a temperature of:
1. $$27.5^{\circ}\mathrm {C}$$
2. $$25^{\circ}\mathrm {C}$$
3. $$30^{\circ}\mathrm {C}$$
4. $$33^{\circ}\mathrm {C}$$

Subtopic:  Thermal Expansion |
65%
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A constrained steel rod of length l, area of cross-section A, Young's modulus Y and coefficient of linear expansion $\alpha$ is heated through $$t^{\circ}\mathrm{C}$$. The work that can be performed by the rod when heated is:
1. (YA$\alpha$t)(l$\alpha$t)
2. $\frac{1}{2}$(YA$\alpha$t)(l$\alpha$t)
3. $\frac{1}{2}$(YA$\alpha$t)$\frac{1}{2}$(l$\alpha$t)
4. 2(YA$\alpha$t)(l$\alpha$t)

Subtopic:  Thermal Stress |
63%
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Two rods, A and B, of different materials having the same cross-sectional area are welded together as shown in the figure. Their thermal conductivities are ${K}_{1}$ and ${K}_{2}$. The thermal conductivity of the composite rod will be:

1. $\frac{{K}_{1}+{K}_{2}}{2}$
2. $\frac{3\left({K}_{1}+{K}_{2}\right)}{2}$
3. ${K}_{1}+{K}_{2}$
4. $2\left({K}_{1}+{K}_{2}\right)$

Subtopic:  Conduction |
78%
From NCERT
NEET - 2017
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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 watts would be:

 1 225 2 450 3 1000 4 1800
Subtopic:  Stefan-Boltzmann Law |
74%
From NCERT
NEET - 2017
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The coefficients of linear expansion of brass and steel rods are α1 and α2, lengths of brass and steel rods are l1 and l2 respectively. If (l2 - l1) is maintained the same at all temperatures, Which one of the following relations holds good?

1. α1l22 = α2l12

2. α12l= α22l1

3. α1l= α2l2

4. α1l= α2l1

Subtopic:  Thermal Expansion |
83%
From NCERT
NEET - 2016
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A black body is at a temperature of 5760 K. The energy of radiation emitted by the body at a wavelength of 250 nm is U1, at a wavelength of 500 nm is U2 and that at 1000 nm is U3. Given Wien's constant $b=2.88×{10}^{6}$ of the following is correct?
1. U3=0
2. U1>U2
3. U2>U1
4. U1=0

Subtopic:  Wien's Displacement Law |
52%
From NCERT
NEET - 2016
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A piece of ice falls from a height $$h$$ so that it melts completely. Only one-quarter of the heat produced is absorbed by the ice, and all energy of ice gets converted into heat during its fall. The value of $$h$$ is: (Latent heat of ice is $$3.4\times10^5$$ J/kg and $$g=10$$ N/kg)

 1 $$544$$ km 2 $$136$$ km 3 $$68$$  km 4 $$34$$ km
Subtopic:  Calorimetry |
75%
From NCERT
NEET - 2016
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