A body cools down from \(80^{\circ}\mathrm{C}\) \(70^{\circ}\mathrm{C}\)
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. |
If 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. |
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. \(33^{\circ}\mathrm {C}\)
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 \(t^{\circ}\text{C}\). 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. \(2(YA\alpha t)(l\alpha t)\)
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. \(122.4\)
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 and . The thermal conductivity of the composite rod will be:
1.
2.
3.
4.
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 |
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. α12l2 = α22l1
3. α1l1 = α2l2
4. α1l2 = α2l1
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 of the following is correct?
1. U3=0
2. U1>U2
3. U2>U1
4. U1=0
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 |